java基础第十讲——数据库、单例设计模式、服务器、项目(数据库—服务器—网络)

目录

数据库
单例设计模式
单例设计模式与数据库的结合
PreparedStatement
MVC设计模式
事务
服务器
项目(数据库—服务器—网络)

数据库

MySQL(在windows下忽略大小写)

DATABASE 数据库
TABLE 表
字段 属性 主键(一个TABLE中不能重复，能够使用这个值确定一条数据) 外键(一个表中的数据持有别的表中的主键)
auto_increment 主键自增长
创建数据库

CREATE DATABASE Clazz

创建表

CREATE TABLE Student(Sno int NOT NULL PRIMARY KEY AUTO_INCREMENT,Sname varchar(30) NOT NULL, Ssex char(3),Sage char(3));

增 insert

insert into Student values (1,'King','男','21')

删 delete

delete from Student where Sname = 'Gone'

改 update

update Student set Sage = '25' where Sname = 'Went'

查 select

select Sname,Ssex,Sage from Student where Sage>20

/** * jdbc的连接测试 *  * @author Administrator * */public class Test {    public static void main(String[] args) {        // 连接数据库的驱动        String driver = "com.mysql.jdbc.Driver";        // URL指向要访问的数据库名        String url = "jdbc:mysql://localhost:3306/Clazz";        // MySQL配置时的用户名        String user = "root";        // java连接MySQL配置时的密码        String password = "123456";        try {            Class.forName(driver);//加载驱动            Connection connection = DriverManager.getConnection(url, user, password);            Statement statement = connection.createStatement();            String insert = "insert into Student (Sname,Ssex,Sage) values('WZ','男','28')";// 增            String delete = "delete from Student where Sno = '2012200968'";// 删            String update = "update Student set Sname = 'Wz' where Sname = 'WZ'";// 改            String select = "select * from Student";// 查 ////          statement.execute(insert);// 增、删、改的时候用execute()            ResultSet resultSet = statement.executeQuery(select);// 查的时候用executeQuery()            resultSet.first();// 先把游标放在第一位            while (!resultSet.isAfterLast()) {// 判断游标是否在最后一位的后边                String name = resultSet.getString("Sname");                String age = resultSet.getString("Sage");                resultSet.next();// 游标下移                System.out.println(name+" "+age);            }        } catch (ClassNotFoundException e) {            e.printStackTrace();        } catch (SQLException e) {            e.printStackTrace();        }    }}

结果

单例设计模式

单例设计模式
让其他类调用时只创建一个对象

1、将构造器改为private修饰
2、私有静态属性
3、写一个public static(可以加一个锁，防止多线程是创建多个对象)方法 用static可以

让其他类用”.”调用

单例设计模式与数据库的结合

public class SQLManager {    //单例设计模式    private Statement statement;    public Statement getStatement() {        return statement;    }    public void setStatement(Statement statement) {        this.statement = statement;    }    //2、声明私有静态本类的对象    private static SQLManager manager;    //3、静态公有的线程锁的方法 返回当前类的对象    public static synchronized SQLManager newInstence(){        if (manager == null) {            manager = new SQLManager();        }        return manager;    }    //1、私有构造方法    private SQLManager(){        //连接数据库的驱动        String driver = "com.mysql.jdbc.Driver";        //URL指向要访问的数据库名        String url = "jdbc:mysql://localhost:3306/Users";        //MySQL配置时的用户名        String user = "root";        //java连接MySQL配置时的密码        String password = "123456";        try {            Class.forName(driver);            Connection connection = DriverManager.getConnection(url, user, password);            if (!connection.isClosed()) {                statement = connection.createStatement();                statement.execute("create table if not exists user"                        + "(id int NOT NULL PRIMARY KEY AUTO_INCREMENT ,user_name varchar(30) NOT NULL,password varchar(20))");                System.out.println("已连接");            }        } catch (ClassNotFoundException e) {            // TODO Auto-generated catch block            e.printStackTrace();        } catch (SQLException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }    }}

注册时

button.addActionListener(new ActionListener() {            public void actionPerformed(ActionEvent arg0) {                String username = textField.getText();                char[] passwords = passwordField.getPassword();//得到密码框中显式密码，返回的是char[]                String password = "";                for (int i = 0; i < passwords.length; i++) {                    password += passwords[i];                }                //用正则表达式检测用户名和密码是否符合规范                Pattern patternName = Pattern.compile("^\\w+$");                 Matcher matcherName = patternName.matcher(username);                boolean name = matcherName.matches();                Pattern patternPassword = Pattern.compile("^\\w+$");                Matcher matcherPassword = patternPassword.matcher(password);                boolean word = matcherPassword.matches();                if (name&&word) {                    Statement statement = SQLManager.newInstence().getStatement();                    String select = String.format("select * from user where user_name = '%s'", username);                    try {                        ResultSet result = statement.executeQuery(select);                        result.last();//找到符合用户名的信息的最后一个                        int i = result.getRow();//得到最后一个符合用户名的行数                        if (i>0) {                            System.out.println("此用户已注册");                        }else {                            String insert = String.format("insert into user(user_name,password) values('%s','%s')", username,password);                            statement.execute(insert);                            System.out.println("注册成功");                        }                    } catch (SQLException e) {                        e.printStackTrace();                    }                }else if (!name) {                    System.out.println("名称不符合注册标准");                }else if (!word) {                    System.out.println("密码不符合标准");                    passwordField.setText("");                }            }        });

登录时

button_1.addActionListener(new ActionListener() {            public void actionPerformed(ActionEvent e) {                Statement st = SQLManager.newInstence().getStatement();                String username = textField.getText();                char[] passwords = passwordField.getPassword();                String password = "";                for (char c : passwords) {                    password += c;                }                String select = String.format("select * from user where user_name = '%s' and password = '%s'", username,password);                try {                    ResultSet result = st.executeQuery(select);                    result.last();                    int num = result.getRow();                    if (num>0) {                        System.out.println("登录成功");                    }else {                        System.out.println("未注册");                    }                } catch (SQLException e1) {                    e1.printStackTrace();                }            }        });

PreparedStatement

Statement时’or 1=’1 会自登陆，对程序造成影响
一般用PreparedStatement
statement.setString(1, username);第一个参数是语句中的第几个”?”,第二个参数是当前”?”需要传入的值。

public boolean SignIn(String username,String password) {        Connection connection = SQLManager.newInstence().getConnection();        try {            if (!connection.isClosed()) {                //用PreparedStatement消除'or 1='1的现象                PreparedStatement preparedStatement = connection.prepareStatement("select * from user where user_name = ? and password = ?");                preparedStatement.setString(1, username);                preparedStatement.setString(2, password);                ResultSet resultSet = preparedStatement.executeQuery();                resultSet.last();                int num = resultSet.getRow();                return num == 1;            }        } catch (SQLException e2) {            // TODO Auto-generated catch block            e2.printStackTrace();        }        return false;    }

MVC设计模式

一种设计模式，也是一种必须学会的编程思想
Model-View-Control
模型(model)－视图(view)－控制器(controller)。模型、视图、控制器的分层处理

/** * 此类只进行数据库的连接 * @author Administrator * */public class SQLManager {    //单例设计模式    private Statement statement;    private Connection connection;    public Connection getConnection() {        return connection;    }    public void setConnection(Connection connection) {        this.connection = connection;    }    public Statement getStatement() {        return statement;    }    public void setStatement(Statement statement) {        this.statement = statement;    }    //2、声明私有静态本类的对象    private static SQLManager manager;    //3、静态公有的线程锁的方法 返回当前类的对象    public static synchronized SQLManager newInstence(){        if (manager == null) {            manager = new SQLManager();        }        return manager;    }    //1、私有构造方法    private SQLManager(){        init();    }    public void init(){        //连接数据库的驱动                String driver = "com.mysql.jdbc.Driver";                //URL指向要访问的数据库名                String url = "jdbc:mysql://localhost:3306/Users";                //MySQL配置时的用户名                String user = "root";                //java连接MySQL配置时的密码                String password = "123456";                try {                    Class.forName(driver);                    connection = DriverManager.getConnection(url, user, password);                } catch (ClassNotFoundException e) {                    // TODO Auto-generated catch block                    e.printStackTrace();                } catch (SQLException e) {                    // TODO Auto-generated catch block                    e.printStackTrace();                }    }}

/** * 此类只进行数据库中的信息交互 * @author Administrator * */public class SQLOperate {    private SQLOperate() {    }    public synchronized static SQLOperate newInstance(){        if (operate == null) {            operate = new SQLOperate();        }        return operate;    }    private static SQLOperate operate;    /**     * 用户登录的数据操作     * @param username  用户名     * @param password  密码     * @return  如果true表示登录成功，false表示登录失败     */    public boolean SignIn(String username,String password) {        Connection connection = SQLManager.newInstence().getConnection();        try {            if (!connection.isClosed()) {                //用PreparedStatement消除'or 1='1的现象                PreparedStatement preparedStatement = connection.prepareStatement("select * from user where user_name = ? and password = ?");                preparedStatement.setString(1, username);                preparedStatement.setString(2, password);                ResultSet resultSet = preparedStatement.executeQuery();                resultSet.last();                int num = resultSet.getRow();                return num == 1;            }        } catch (SQLException e2) {            // TODO Auto-generated catch block            e2.printStackTrace();        }        return false;    }    /**     * 用户注册时的数据操作     * @param username  用户名     * @param password  用户密码     */    public void DengLu(String username,String password){        Connection connection = SQLManager.newInstence().getConnection();        try {            PreparedStatement statement = connection.prepareStatement("select * from user where user_name = ?");            statement.setString(1, username);            ResultSet set = statement.executeQuery();            set.last();            int num = set.getRow();            if (num>0) {                System.out.println("此用户名已注册");            }else {                PreparedStatement statement2 = connection.prepareStatement("insert into user(user_name,password) values(?,?)");                statement2.setString(1, username);                statement2.setString(2, password);                statement2.execute();                System.out.println("注册成功");            }        } catch (SQLException e) {            e.printStackTrace();        }    }}

//注册的视图(部分)public void actionPerformed(ActionEvent arg0) {                String username = textField.getText();                char[] passwords = passwordField.getPassword();//得到密码框中显式密码，返回的是char[]                String password = "";                for (int i = 0; i < passwords.length; i++) {                    password += passwords[i];                }                //用正则表达式检测用户名和密码是否符合规范                Pattern patternName = Pattern.compile("^\\w+$");                 Matcher matcherName = patternName.matcher(username);                boolean name = matcherName.matches();                Pattern patternPassword = Pattern.compile("^\\w+$");                Matcher matcherPassword = patternPassword.matcher(password);                boolean word = matcherPassword.matches();                if (name&&word) {                    SQLOperate.newInstance().DengLu(username, password);//调用数据库造作类中的方法，实现分层                }else if (!name) {                    System.out.println("名称不符合注册标准");                }else if (!word) {                    System.out.println("密码不符合标准");                    passwordField.setText("");                }            }//登录时的视图(部分)public void actionPerformed(ActionEvent e) {                String username = textField.getText();                char[] passwords = passwordField.getPassword();                String password = "";                for (char c : passwords) {                    password += c;                }                boolean isSignIn = SQLOperate.newInstance().SignIn(username, password);                if (isSignIn) {                    System.out.println("登录成功");                }else {                    System.out.println("登录失败");                }            }

事务

事务(一组不可拆分的操作) 关键字commit
例：银行ATM提款 输入金额-播放录音-打开取钱口-吐钱-钱拿。其中有一个出错就无法取款。即回滚到初始位置
//将connection设置为不自动提交
connection.setAutoCommit(false);
…需要执行的代码块
statement.addBatch(sql)将sql语句添加到执行列表中统一执行
statement.executeBatch();执行列表中的语句
(可以提高SQL语句的执行效率)
…
connection.commit();//从connection.setAutoCommit(false)到commit是一个事务，中间一条出错，会回滚至前边。

String sql1 = "insert into user(user_name,password) values ('fsdkjhs','sdf')";                    String sql2 = "insert into user(user_name,password) values ('fsdkjs','sdfd')";                    String sql3 = "insert into user(user_name,passwords) values ('fsdkjdashs','sddfsf')";                    String sql4 = "insert into user(user_name,password) values ('fs','sdf')";                    String sql5 = "insert into user(user_name,password) values ('ffdssdkjhs','sdsf')";                    //数据库连接默认每一条sql语句是一个事务，会单独执行，自动提交                    //将connection设置为不自动提交                    connection.setAutoCommit(false);//                  statement.addBatch(sql)将sql语句添加到执行列表中统一执行                    statement.addBatch(sql1);                    statement.addBatch(sql2);                    statement.addBatch(sql3);                    statement.addBatch(sql4);                    statement.addBatch(sql5);                    statement.executeBatch();                    connection.commit();//从connection.setAutoCommit(false)到commit是一个事务，中间一条出错，会回滚至前边。

服务器

搭建一个服务器 创建serverlet用来给前端提供数据使用tomcat
新建一个Dynamic Web Project
在WebContent中新建一个index.xml如图
在index.xml中的

<body>    <a> HelloWorld!</a></body>

运行后如图：
将其生成的地址复制到浏览器上：

搭建一个简易服务器：

搭建服务器ServLet
HTTpUrlConnection
HTTpClient

(服务器与用户之间的信息交互)

新建一个Servlet
soGet 直接连接在url后边，是显式的
doPost 隐式的，比doGet安全

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {//其中第一个参数是指用户向服务器提交的数据。//第二个参数是指服务器向用户发送的数据。        // TODO Auto-generated method stub        response.getWriter().append("Served at: ").append(request.getContextPath());    }

doGet方法在网址后边跟上要提交的数据 用?隔开,例如：
localhost:8080/MyServiceTest?username=zhangsan&password=1234
注：”?”前没有”/”

用户与服务器之间的交互：（doGet方法）
使用浏览器提交数据默认的编码格式ISO-8859-1 得到string username编码格式8859-1

/** * 此类为汉字编码的转变类 * @author Administrator * */public class Encoding {    /**     * 将ISO-8859-1的字符串转换成UTF-8的字符串     * @param string    需要转换的字符串     * @return  返回转换好的字符串     */    public static String getEncoding(String string) {        try {            byte[] array = string.getBytes("ISO-8859-1");            string = new String(array, "UTF-8");        } catch (UnsupportedEncodingException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }        return string;    }}/** * Servlet implementation class MyServlet */@WebServlet("/MyServlet")public class MyServlet extends HttpServlet {    private static final long serialVersionUID = 1L;    /**     * @see HttpServlet#HttpServlet()     */    public MyServlet() {        super();        // TODO Auto-generated constructor stub    }    /**     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)     */    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {        // TODO Auto-generated method stub//      response.getWriter().append("Served at: ").append(request.getContextPath());        String username = request.getParameter("username");        String passwrod = request.getParameter("password");        username = Encoding.getEncoding(username);//将用户提交给服务器的ISO-8859-1字符串转型成UTF-8        String s = "得到的用户名："+username+"密码："+passwrod;        System.out.println(s);        response.setHeader("Content-type", "text/html;charset=UTF-8");        //让浏览器以UTF-8编码格式解析        response.getWriter().append(s);    }    /**     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)     */    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {        // TODO Auto-generated method stub        doGet(request, response);    }}

HTTpUrlConnection

doGet方法

    /**     * HTTpUrlConnection的doGet方法     * @param username  用户名     * @param password  密码     */    public void HTTpUrldoGet(String username, String password) {        String urlString = "http://localhost:8080/HTTpTest_Servelet//ServeletTest?username=" + username + "&"                + "password=" + password;        try {            URL url = new URL(urlString);            HttpURLConnection connection = (HttpURLConnection) url.openConnection();            connection.setRequestMethod("GET");            // 设置接受的数据类型            connection.setRequestProperty("Accept-Charset", "utf-8");            // 设置可以接受序列化的java对象            connection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");            int code = connection.getResponseCode();            System.out.println(code);            if (code == HttpURLConnection.HTTP_OK) {                InputStream is = connection.getInputStream();                BufferedReader br = new BufferedReader(new InputStreamReader(is));                String line = br.readLine();                while (line != null) {                    System.out.println(line);                    line = br.readLine();                }            }        } catch (MalformedURLException e) {            // TODO Auto-generated catch block            e.printStackTrace();        } catch (IOException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }    }

doPost方法

    /**     * HTTpUrlConnection的doPost方法     * @param username  用户名     * @param password  密码     */    public void HTTpUrldoPost(String username, String password) {        String urlString = "http://localhost:8080/HTTpTest_Servelet//ServeletTest";        try {            URL url = new URL(urlString);            HttpURLConnection connection = (HttpURLConnection) url.openConnection();            connection.setRequestMethod("POST");            // 设置接受的数据类型            connection.setRequestProperty("Accept-Charset", "utf-8");            // 设置可以接受序列化的java对象            connection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");            //设置可以读取服务器返回的信息，默认为ture            connection.setDoInput(true);            //设置客户端可以给服务器提交信息，默认是false。post方法必须设置为true            connection.setDoOutput(true);            //post方法不允许使用缓存            connection.setUseCaches(false);            String params = "username="+username+"&password="+password;            connection.getOutputStream().write(params.getBytes());            int code = connection.getResponseCode();            System.out.println(code);            if (code == HttpURLConnection.HTTP_OK) {                InputStream is = connection.getInputStream();                BufferedReader br = new BufferedReader(new InputStreamReader(is));                String line = br.readLine();                while(line!=null){                    System.out.println(line);                    line = br.readLine();                }            }        } catch (IOException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }    }

HTTpClient

doGet方法

    /**     * HTTpClient的doGet方法     * @param username  用户名     * @param password  密码     */    public static void HTTpClientdoGet(String username,String password) {        String urlString = "http://localhost:8080/HTTpTest_Servelet//ServeletTest?username=" + username + "&"                + "password=" + password;        HttpClientBuilder builder = HttpClientBuilder.create();//创建HttpClientBuilder        HttpClient client = builder.build();        HttpGet get = new HttpGet(urlString);//得到get方法        get.setHeader("Content-Type", "application/x-www-form-urlencoded; charset=UTF-8");//设定服务器接收后数据的读取方式为utf-8        try {            HttpResponse response = client.execute(get);//执行            StatusLine statusLine =  response.getStatusLine();//获得返回的的表头，包含HTTp状态码            int code = statusLine.getStatusCode();//获得HTTp状态码            System.out.println(code);            if (code == HttpURLConnection.HTTP_OK) {                HttpEntity entity = response.getEntity();//得到返回的数据实体                InputStream is = entity.getContent();//得到输入流                BufferedReader br = new BufferedReader(new InputStreamReader(is));                String line = br.readLine();                while(line!=null){                    System.out.println(line);                    line = br.readLine();                }            }        } catch (IOException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }    }

doPost方法

    /**     * HTTpClient的doPost方法     * @param username  用户名     * @param password  密码     */    public static void HTTpClientdoPost(String username,String password) {        String urlString = "http://localhost:8080/HTTpTest_Servelet//ServeletTest";        HttpClientBuilder builder = HttpClientBuilder.create();        HttpClient client = builder.build();        HttpPost post = new HttpPost(urlString);//设置post方法        NameValuePair pair1 = new BasicNameValuePair("username", username);//设置参数        NameValuePair pair2 = new BasicNameValuePair("password", password);        ArrayList<NameValuePair> list = new ArrayList<>();//将参数放进参数列表        list.add(pair1);        list.add(pair2);        try {            post.setEntity(new UrlEncodedFormEntity(list,"UTF-8"));//设置发送到服务器的数据的格式为utf-8            post.setHeader("Content-Type", "application/x-www-form-urlencoded; charset=UTF-8");//设定服务器接收后数据的读取方式为utf-8            HttpResponse response = client.execute(post);//执行            StatusLine statusLine = response.getStatusLine();//获得返回过来的表头，包含Http的状态码            int code = statusLine.getStatusCode();            if (code==HttpURLConnection.HTTP_OK) {                HttpEntity entity = response.getEntity();//得到数据实体                InputStream is = entity.getContent();                BufferedReader br = new BufferedReader(new InputStreamReader(is));                String line = br.readLine();                while(line!=null){                    System.out.println(line);                    line = br.readLine();                }            }        } catch (UnsupportedEncodingException e) {            // TODO Auto-generated catch block            e.printStackTrace();        } catch (ClientProtocolException e) {            // TODO Auto-generated catch block            e.printStackTrace();        } catch (IOException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }    }

项目(网络—服务器—数据库)

1.服务器导包tomact。lib文件夹下mysql包、json包
2.界面中导包json包
注意：MVC编程思想
界面：

    //登录的按钮    JButton btnHttpclientdopost = new JButton("登录");        btnHttpclientdopost.addActionListener(new ActionListener() {            public void actionPerformed(ActionEvent e) {                String username = textField.getText();                char[] array = passwordField.getPassword();                String password = "";                for (char c : array) {                    password += c;                }                //用正则表达式检测用户名和密码是否符合规范                Pattern patternName = Pattern.compile("^\\w+$");                 Matcher matcherName = patternName.matcher(username);                boolean name = matcherName.matches();                Pattern patternPassword = Pattern.compile("^\\w+$");                Matcher matcherPassword = patternPassword.matcher(password);                boolean word = matcherPassword.matches();                if (name&&word) {                    String line = HttpClientOperate.newInstance().login(username, password);                    System.out.println(line);//调用网络操作中的登录方法                    //显示登录后的界面                EventQueue.invokeLater(new Runnable() {                    public void run() {                        try {                            SelectFrame frame = new SelectFrame();                            frame.setVisible(true);                        } catch (Exception e) {                            e.printStackTrace();                        }                    }                });            }        });                }else if (!name) {                    System.out.println("名称不符合注册标准");                }else if (!word) {                    System.out.println("密码不符合标准");                    passwordField.setText("");                }    //注册的按钮    JButton button = new JButton("还没注册?注册");        button.addActionListener(new ActionListener() {            public void actionPerformed(ActionEvent arg0) {            //调用注册的界面                EventQueue.invokeLater(new Runnable() {                    public void run() {                        try {                            RegisterFrame frame = new RegisterFrame();                            frame.setVisible(true);                        } catch (Exception e) {                            e.printStackTrace();                        }                    }                });            }        });/**登录后的界面按钮*/JButton button = new JButton("查询所有人");        button.addActionListener(new ActionListener() {            public void actionPerformed(ActionEvent arg0) {                String line = HttpClientOperate.newInstance().select();//调用网络操作中的查询方法                System.out.println(line);//              textArea.setText(line);            }        });     /**注册的界面按钮*/JButton button = new JButton("注册");        button.addActionListener(new ActionListener() {            public void actionPerformed(ActionEvent arg0) {                HttpClientOperate.newInstance().setType("register");//设置reister注册的type                String username = textField.getText();                char[] array = passwordField.getPassword();                String password = "";                for (char c : array) {                    password += c;                }                //用正则表达式检测用户名和密码是否符合规范                Pattern patternName = Pattern.compile("^\\w+$");                 Matcher matcherName = patternName.matcher(username);                boolean name = matcherName.matches();                Pattern patternPassword = Pattern.compile("^\\w+$");                Matcher matcherPassword = patternPassword.matcher(password);                boolean word = matcherPassword.matches();                if (name&&word) {                    String line = HttpClientOperate.newInstance().register(username, password);//调用网络操作中的注册方法                    System.out.println(line);                }else if (!name) {                    System.out.println("名称不符合注册标准");                }else if (!word) {                    System.out.println("密码不符合标准");                    passwordField.setText("");                }            }        });     

点击按钮后的网络操作

/** * 点击按钮后的网络操作 * @author Administrator * */public class HttpClientOperate {    public HttpClientOperate() {    }    private static HttpClientOperate operate;    public static HttpClientOperate newInstance() {        if (operate == null) {            operate = new HttpClientOperate();        }        return operate;    }    /**     * 根据type得到Register 将json提交到服务器,并接收服务器返回的json，并解析     * @param username     * @param password     * @return  返回json     */    public String register(String username,String password) {        JSONObject object = new  JSONObject();        object.put("type", "Register");        JSONObject data = new JSONObject();        data.put("username", username);        data.put("password", password);        object.put("data", data);        String urlString = "http://localhost:8080/MyServiceTest//MyServlet";        HttpClientBuilder builder = HttpClientBuilder.create();        HttpClient client = builder.build();        HttpPost post = new HttpPost(urlString);        NameValuePair pair = new BasicNameValuePair("json", object.toString());        ArrayList<NameValuePair> list = new ArrayList<>();        list.add(pair);        try {            post.setEntity(new UrlEncodedFormEntity(list,"UTF-8"));            post.setHeader("Content-Type", "application/x-www-form-urlencoded; charset=UTF-8");            HttpResponse response =client.execute(post);            int code = response.getStatusLine().getStatusCode();            System.out.println(code);            if (code == HttpURLConnection.HTTP_OK) {                HttpEntity entity = response.getEntity();                InputStream is = entity.getContent();                BufferedReader br = new BufferedReader(new InputStreamReader(is));                StringBuffer buffer = new StringBuffer();                String line = br.readLine();                while(line!=null){                    buffer.append(line);                    line = br.readLine();                }                return buffer.toString();            }        } catch (UnsupportedEncodingException e) {            // TODO Auto-generated catch block            e.printStackTrace();        } catch (ClientProtocolException e) {            // TODO Auto-generated catch block            e.printStackTrace();        } catch (IOException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }        return null;    }    /**     * 根据type得到Login 将json提交到服务器,并接收服务器返回的json，并解析     * @param username     * @param password     * @return  返回json     */    public String login(String username,String password) {        JSONObject object = new  JSONObject();        object.put("type", "Login");        JSONObject data = new JSONObject();        data.put("username", username);        data.put("password", password);        object.put("data", data);        String urlString = "http://localhost:8080/MyServiceTest//MyServlet";        HttpClientBuilder builder = HttpClientBuilder.create();        HttpClient client = builder.build();        HttpPost post = new HttpPost(urlString);        NameValuePair pair = new BasicNameValuePair("json", object.toString());        ArrayList<NameValuePair> list = new ArrayList<>();        list.add(pair);        try {            post.setEntity(new UrlEncodedFormEntity(list,"UTF-8"));            post.setHeader("Content-Type", "application/x-www-form-urlencoded; charset=UTF-8");            HttpResponse response =client.execute(post);            int code = response.getStatusLine().getStatusCode();            System.out.println(code);            if (code == HttpURLConnection.HTTP_OK) {                HttpEntity entity = response.getEntity();                InputStream is = entity.getContent();                BufferedReader br = new BufferedReader(new InputStreamReader(is));                String line = br.readLine();                StringBuffer buffer = new StringBuffer();                while(line!=null){                    buffer.append(line);                    line = br.readLine();                }                return buffer.toString();            }        } catch (UnsupportedEncodingException e) {            // TODO Auto-generated catch block            e.printStackTrace();        } catch (ClientProtocolException e) {            // TODO Auto-generated catch block            e.printStackTrace();        } catch (IOException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }        return null;    }    /**     * 根据type得到Select 将json提交到服务器,并接收服务器返回的json，并解析     * @param username     * @param password     * @return  返回json     */    public String select() {        JSONObject object = new  JSONObject();        object.put("type", "Select");        String urlString = "http://localhost:8080/MyServiceTest//MyServlet";        HttpClientBuilder builder = HttpClientBuilder.create();        HttpClient client = builder.build();        HttpPost post = new HttpPost(urlString);        NameValuePair pair = new BasicNameValuePair("json", object.toString());        ArrayList<NameValuePair> list = new ArrayList<>();        list.add(pair);        try {            post.setEntity(new UrlEncodedFormEntity(list,"UTF-8"));            post.setHeader("Content-Type", "application/x-www-form-urlencoded; charset=UTF-8");            HttpResponse response =client.execute(post);            int code = response.getStatusLine().getStatusCode();            System.out.println(code);            if (code == HttpURLConnection.HTTP_OK) {                HttpEntity entity = response.getEntity();                InputStream is = entity.getContent();                BufferedReader br = new BufferedReader(new InputStreamReader(is));                String line = br.readLine();                StringBuffer buffer = new StringBuffer();                while(line!=null){                    buffer.append(line);                    line = br.readLine();                }                return buffer.toString();            }        } catch (UnsupportedEncodingException e) {            // TODO Auto-generated catch block            e.printStackTrace();        } catch (ClientProtocolException e) {            // TODO Auto-generated catch block            e.printStackTrace();        } catch (IOException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }        return null;    }}

服务器Servlet

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {        // TODO Auto-generated method stub        //用户通过浏览器向服务器提交信息且输出        String json = request.getParameter("json");        JSONObject obj = JSONObject.fromObject(json);//根据json串得到jsonobject        String type = obj.getString("type");        String massage = "";        //根据type调用不同的方法        if (type.equals(Types.REGISTER)) {            JSONObject data = obj.getJSONObject("data");            String username = data.getString("username");            String password = data.getString("password");            massage = SQLOperate.newIntence().returnRegistMsg(username, password);//调用服务器数据库操作类中的注册方法        }        else if (type.equals(Types.LOGIN)) {            JSONObject data = obj.getJSONObject("data");            String username = data.getString("username");            String password = data.getString("password");            massage = SQLOperate.newIntence().renturnLogin(username, password);//调用服务器数据库操作类中的登录方法        }else if (type.equals(Types.SELECT)) {            massage = SQLOperate.newIntence().renturnSelect();//调用服务器数据库操作类中的查询方法        }        response.setHeader("Content-type", "text/html;charset=UTF-8");//让浏览器以UTF-8编码格式解析        //服务器响应客户端的信息        response.getWriter().append(massage);    }    /**     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)     */    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {        // TODO Auto-generated method stub        doGet(request, response);    }/** * 注册类型的常量类 * @author Administrator * */public class Types {    /**注册的类型*/    public static final String REGISTER = "Register";    /**登录的类型*/    public static final String LOGIN = "Login";    /**查询的类型*/    public static final String SELECT = "Select";}

服务器的数据库连接类

/** * 数据库连接类 * @author Administrator * */public class SQLManage {    private Connection connection;    public Connection getConnection() {        return connection;    }    private static SQLManage manage;    public static synchronized SQLManage newInstance() {        if (manage == null) {            manage = new SQLManage();        }        return manage;    }    private SQLManage(){        String driver = "com.mysql.jdbc.Driver";        String url = "jdbc:mysql://localhost:3306/users";        String user = "root";        String password = "123456";        try {            Class.forName(driver);            connection = DriverManager.getConnection(url, user, password);        } catch (ClassNotFoundException e) {            e.printStackTrace();        } catch (SQLException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }    }}

服务器的数据库操作类

/** * 数据库操作类 * @author Administrator * */public class SQLOperate {    public SQLOperate() {    }    private static SQLOperate operate;    public static synchronized SQLOperate newIntence() {        if (operate == null) {            operate = new SQLOperate();        }        return operate;    }    /**     * 数据库中注册的方法     * @param username  用户名     * @param passwrod  密码     * @return  返回结果信息     */    public String returnRegistMsg(String username,String password) {        int code = 0;        JSONObject obj = new JSONObject();        Connection connection = SQLManage.newInstance().getConnection();        try {            PreparedStatement statement = connection.prepareStatement("select * from user where user_name = ?");            statement.setString(1, username);            ResultSet set = statement.executeQuery();            set.last();            int num = set.getRow();            if (num>0) {                obj.put("code", 0);                obj.put("message", "用户名被注册");            }else {                PreparedStatement statement2 = connection.prepareStatement("insert into user(user_name,password)values(?,?)");                statement2.setString(1, username);                statement2.setString(2, password);                statement2.execute();                obj.put("code", 1);                obj.put("message", "注册成功");            }        } catch (SQLException e) {            // TODO Auto-generated catch block            obj.put("code", 0);            obj.put("message", "注册失败");            e.printStackTrace();        }        return obj.toString();    }    /**     * 数据库中登录的方法     * @param username  用户名     * @param passwrod  密码     * @return  返回结果信息     */    public String renturnLogin(String username,String password){        int code = 0;        JSONObject obj = new JSONObject();        Connection connection = SQLManage.newInstance().getConnection();        try {            PreparedStatement statement =connection.prepareStatement("select * from user where user_name = ?");            statement.setString(1, username);            ResultSet resultSet = statement.executeQuery();            resultSet.last();            int num = resultSet.getRow();            if (num>0) {                PreparedStatement statement2 = connection.prepareStatement("select * from user where password = ? and user_name = ?");                statement2.setString(1, password);                statement2.setString(2, username);                ResultSet resultSet2 = statement2.executeQuery();                resultSet2.last();                int num2 = resultSet2.getRow();                if (num2>0) {                    obj.put("code", 1);                    obj.put("massage", "登陆成功");                }else {                    obj.put("code",0 );                    obj.put("massage", "密码不正确");                }            }else {                obj.put("code", 2);                obj.put("massage", "此用户未注册");            }        } catch (SQLException e) {            // TODO Auto-generated catch block            obj.put("code", 0);            obj.put("massage", "登录失败");            e.printStackTrace();        }        return obj.toString();    }    /**     * 数据库中查询的方法     * @return  返回结果信息     */    public String renturnSelect(){        int code = 0;        JSONObject obj = new JSONObject();        Connection connection = SQLManage.newInstance().getConnection();        try {            PreparedStatement statement =connection.prepareStatement("select * from user ");            ResultSet resultSet = statement.executeQuery();            resultSet.first();            JSONArray array = new JSONArray();            while(!resultSet.isAfterLast()){                JSONObject item = new JSONObject();                item.put("name", resultSet.getString("user_name"));                array.add(item);                resultSet.next();            }            obj.put("code", 1);            obj.put("name", array);            obj.put("massage", "成功");        } catch (SQLException e) {            // TODO Auto-generated catch block            obj.put("code", 0);            obj.put("massage", "查询失败");            e.printStackTrace();        }        return obj.toString();    }}