《老罗Android》学习之服务器端Web编程

1. JavaWeb实现用户注册功能 
  框架：Register之下分成三个包：
action：控制层，dao：数据访问层，service：服务层
这就是标准的MVC的开发模式。
action包下：RegisterServlet.java ，从页面得到注册信息，注册到mySQL中去。

@WebServlet("/RegisterServlet")public class RegisterServlet extends HttpServlet {private static final long serialVersionUID = 1L;private RegisterService service;       public RegisterServlet() {        super();    }protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {this.doPost(request,response);  //都用doPost方法}protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {String path = request.getContextPath();//获得上下文路径response.setContentType("text/html;charset=utf-8");//服务器端的编码格式，客户端提交页码的格式要一致PrintWriter out = response.getWriter(); //打印信息String username = request.getParameter("username");String pswd = request.getParameter("pswd");String realname = request.getParameter("realname");List<Object> params = new ArrayList<Object>();params.add(username);params.add(pswd);params.add(realname);;out.println("-username--->:"+username);boolean flag = service.registerUser(params);  //注册if (flag) {request.getSession().setAttribute("username", username);response.sendRedirect(path + "/main.jsp");}out.flush();out.close();}@Overridepublic void init() throws ServletException {service = new RegisterDao();  //生成注册对象} }

dao包下：RegisterDao.java， 调用JDBC去实现注册的功能

public class RegisterDao implements RegisterService{private JdbcUtils utils = null;public RegisterDao() {utils = new JdbcUtils();}//完成了对用户注册的dao的编写@Overridepublic boolean registerUser(List<Object> params) {boolean flag = false;String sql = "insert into user(username,pswd,realname) values(?,?,?)";try {// 先获得链接utils.getConnection();flag = utils.updateByPreparedStatement(sql, params);System.out.println("-flag-->>" + flag);} catch (Exception e) {e.printStackTrace();//打印出出错信息} finally {// 关闭数据库的链接utils.releaseConn();}return flag;}}

service包下：RegisterService.java， 定义注册的接口

public interface RegisterService {//完成用户的注册功能public boolean registerUser(List<Object> params);}

2. JavaWeb实现用户登录功能 
  框架：Login之下同样分成三个包：
action：控制层，dao：数据访问层，service：服务层
action包下：LoginServlet.java ，查找SQL数据库中是否已经注册了这个用户。

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {String path = request.getContextPath(); //获得路径response.setContentType("text/html;charset=utf-8");PrintWriter out = response.getWriter();String username = request.getParameter("username");String pswd = request.getParameter("pswd");   //得到用户和密码List<Object> params = new ArrayList<Object>();params.add(username);params.add(pswd);boolean flag = service.login(params);  //调用login方法if (flag) {request.getSession().setAttribute("username", username);response.sendRedirect(path + "/main.jsp");//跳转到主界面}out.flush();out.close();}

dao包下：LoginDao.java， 调用JDBC去实现查询功能

public boolean login(List<Object> params) {boolean flag = false;String sql = "select * from user where username=? and pswd=?";try {jdbcUtils.getConnection();Map<String, Object> map = jdbcUtils.findSimpleResult(sql, params);flag = !map.isEmpty() ? true : false;//空是默认值} catch (Exception e) {e.printStackTrace();} finally {jdbcUtils.releaseConn();}return flag;}

service包下：LoginService.java， 定义查询的接口.
2.增加过滤功能
新建MyFilter的class,让它实现javax.servlet(自己添加的包servlet-api-2.4.jar)  Interface.

public class MyFilter implements Filter {public MyFilter() {}@Overridepublic void destroy() {}@Overridepublic void doFilter(ServletRequest request, ServletResponse response,FilterChain chain) throws IOException, ServletException {// 过滤用户的请求，判断是否登录HttpServletRequest httpServletRequest = (HttpServletRequest) request;//请求String path = httpServletRequest.getContextPath();HttpServletResponse httpServletResponse = (HttpServletResponse) response;//响应httpServletRequest.setCharacterEncoding("utf-8");httpServletResponse.setCharacterEncoding("utf-8");String username = (String)httpServletRequest.getSession().getAttribute("username");if (username==null) {     //假如用户名为空时，停在首页httpServletResponse.sendRedirect(path + "/index.jsp");}chain.doFilter(httpServletRequest, httpServletResponse);}@Overridepublic void init(FilterConfig arg0) throws ServletException {}}

WebContent下的web.xml,中要做添加：

<?xml version="1.0" encoding="UTF-8"?><web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">  <servlet>    <description>This is the description of my J2EE component</description>    <display-name>This is the display name of my J2EE component</display-name>    <servlet-name>RegisterServlet</servlet-name>    <servlet-class>com.product.dbutil.register.action.RegisterServlet</servlet-class>  </servlet>  <servlet>    <description>This is the description of my J2EE component</description>    <display-name>This is the display name of my J2EE component</display-name>    <servlet-name>LoginServlet</servlet-name>    <servlet-class>com.product.dbutil.login.action.LoginServlet</servlet-class>  </servlet>  <filter>  <filter-name>MyFilter</filter-name>  <filter-class>com.product.dbutil.filter.MyFilter</filter-class>  </filter> <servlet-mapping>    <servlet-name>RegisterServlet</servlet-name>    <url-pattern>/RegisterServlet</url-pattern>  </servlet-mapping> <servlet-mapping>    <servlet-name>LoginServlet</servlet-name>    <url-pattern>/LoginServlet</url-pattern>  </servlet-mapping>  <filter-mapping>  <filter-name>MyFilter</filter-name>  <url-pattern>/main.jsp</url-pattern>   <!-- 过滤哪个界面 -->  </filter-mapping> <welcome-file-list>    <welcome-file>index.jsp</welcome-file>  </welcome-file-list> </web-app>

 加入Filter之后，就要登录了才能访问main.jsp，直接在地址栏输入http://192.168.0.221:8080/xianfengProject/main.jsp访问不了。