Android学习(二)：解析JSON,GSON,FASTJSON;JDBC编程

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一、android使用JSON

JSON数据格式如下形式（以键值对的形式存在）:

{    "students":    [        {"name":"jack","age":10},        {"name":"Lucy","age":40}    ]}

·解析JSON格式如下例子代码：

·1.首先定义Person类，创建Person.java

package com.qianfeng.domain;public class Person {    private int age;     private String name;    public Person() { // TODO Auto-generated constructor stub }    public Person(int age, String name) { super(); this.age = age; this.name = name; }    public int getAge() { return age; }    public void setAge(int age) { this.age = age; }    public String getName() { return name; }    public void setName(String name) { this.name = name; }    @Override     public String toString() { return "Person [age=" + age + ", name=" + name + "]"; }}

·2.JsonList数据，创建JsonList.java

package com.qianfeng.service;import java.util.ArrayList;import java.util.List;import com.qianfeng.domain.Person;public class JsonList {    public JsonList() {}    public static List<Person> getList() {        List<Person> list = new ArrayList<Person>();        list.add(new Person(1002,"李四2"));        list.add(new Person(1003,"李四3"));        list.add(new Person(1001,"李四1"));        return list;    }    public static Person getPerson(){        return new Person(1002,"李四2");     }}

·3.JSON解析程序，创建JsonTools.java

package com.qianfeng.service;import java.util.ArrayList;import java.util.List;import com.qianfeng.domain.Person;import net.sf.json.JSON;import net.sf.json.JSONArray;import net.sf.json.JSONObject;import net.sf.json.JSONSerializer;public class JsonTools {    public JsonTools() {}    public static String getString(Person person) {        JSON json = JSONSerializer.toJSON(JsonList.getPerson());        return json.toString();    }    public static Person getPerson(String msgString) {        Person person = new Person();        JSONArray array = new JSONArray();        array.add(msgString);        JSONObject obj = array.getJSONObject(0);        // System.out.println(obj.get("age"));        // System.out.println(obj.get("name"));        person.setAge(obj.getInt("age"));        person.setName(obj.getString("name"));        return person;    }    public static String getListString(List<Person> listPersons) {        JSON json = JSONSerializer.toJSON(listPersons);        return json.toString();    }    /**     * 将一个json格式的字符串转换成行对应的对象     * @param str     * @return     */    public static List<Person> getPersons(String str) {        List<Person> list = new ArrayList<Person>();        JSONArray array = new JSONArray();        array.add(str);        JSONArray array2 = array.getJSONArray(0);        for (int i = 0; i <array2.size(); i++) {            JSONObject jsonObject =  array2.getJSONObject(i);            Person person = new Person();            person.setAge(jsonObject.getInt("age"));            person.setName(jsonObject.getString("name"));            list.add(person);        }        return list;    }    /**     * @param args     */    public static void main(String[] args) {        // TODO Auto-generated method stub        // JSON json = JSONSerializer.toJSON(JsonList.getList());        // System.out.println(getString(new Person(23,"jack")));        // System.out.println(getPerson("{'age':1002,'name':'李四2'}").toString());        // System.out.println(getListString(JsonList.getList()));        String msgString = "[{'age':1002,'name':'李四2'},{'age':1003,'name':'李四3'},{'age':1001,'name':'李四1'}]";        List<Person> lPersons = getPersons(msgString);        for(Person p:lPersons){            System.out.println(p.toString());        }    }}

·二、android使用GSON

·ØGson这个Java类库可以把Java对象转换成JSON，也可以把JSON字符串转换成一个相等的Java对象。

·ØGson支持任意复杂Java对象包括没有源代码的对象。

·解析GSON格式如下例子代码：

·1.首先定义Person类，如上述

·2.创建GsonTools.java

package com.android.mygson;import java.util.ArrayList;import java.util.HashMap;import java.util.List;import java.util.Map;import com.android.domain.Person;import com.google.gson.Gson;import com.google.gson.reflect.TypeToken;public class GsonTools {    public GsonTools() {}    public static String createGsonString(Object object) {        Gson gson = new Gson();        String gsonString = gson.toJson(object);        return gsonString;    }    public static <T> T changeGsonToBean(String gsonString, Class<T> cls) {        Gson gson = new Gson();        T t = gson.fromJson(gsonString, cls);        return t;    }    public static <T> List<T> changeGsonToList(String gsonString, Class<T> cls) {        Gson gson = new Gson();        List<T> list_person = gson.fromJson(gsonString,                new TypeToken<List<T>>() {                }.getType());        return list_person;    }    public static List<Map<String, Object>> changeGsonToListMaps(String gsonString) {        List<Map<String, Object>> list = null;        Gson gson = new Gson();        list = gson.fromJson(gsonString,                new TypeToken<List<Map<String, Object>>>() {                }.getType());        return list;    }    public static void main(String[] args) {        // TODO Auto-generated method stub        // Person person1 = new Person("张三1", 24, "北京1");        // Person person2 = new Person("张三2", 23, "北京2");        // List<Person> list = new ArrayList<Person>();        // list.add(person1);        // list.add(person2);        //        // String gsonString = createGsonString(list);        // System.out.println(gsonString);        // Gson gson = new Gson();        // List<Person> list_person = changeGsonToList(gsonString,Person.class);        // System.out.println(list_person.toString());        // Person pp = changeGsonToBean(gsonString,Person.class);        // System.out.println(pp);        List<Map<String, Object>> list = new ArrayList<Map<String, Object>>();        Map<String, Object> map = new HashMap<String, Object>();        map.put("name", "jack");        map.put("age", 23);        Map<String, Object> map2 = new HashMap<String, Object>();        map2.put("name", "rose");        map2.put("age", 24);        list.add(map);        list.add(map2);        String gsonString = createGsonString(list);        System.out.println(gsonString);        List<Map<String, Object>> list2 = changeGsonToListMaps(gsonString);        System.out.println(list2.toString());    }}

·三、android使用阿里巴巴fastjson技术

·ØFastJson是一个Json处理工具包，包括“序列化”和“反序列化”两部分，它具备如下特征：

·Ø速度最快，测试表明，fastjson具有极快的性能，超越任其他的Java Json parser。包括自称最快的JackJson。

·Ø功能强大，完全支持Java Bean、集合、Map、日期、Enum，支持范型，支持自省。

·Ø无依赖，能够直接运行在Java SE 5.0以上版本

·Ø支持Android。

·Ø开源 (Apache 2.0)

·解析GSON格式如下例子代码：

·1.首先定义Person类，如上述

·2.创建FastJsonTools.java

package com.android.myfastjson;import java.util.ArrayList;import java.util.HashMap;import java.util.List;import java.util.Map;import com.alibaba.fastjson.JSON;import com.alibaba.fastjson.TypeReference;import com.alibaba.fastjson.asm.Type;import com.alibaba.fastjson.util.TypeUtils;public class FastJsonTools {    public FastJsonTools() {}    public static String createJsonString(Object object) {        String jsonString = JSON.toJSONString(object);        return jsonString;    }    public static <T> T createJsonBean(String jsonString, Class<T> cls) {        T t = JSON.parseObject(jsonString, cls);        return t;    }    public static <T> List<T> createJsonToListBean(String jsonString,            Class<T> cls) {        List<T> list = null;        list = JSON.parseArray(jsonString, cls);        return list;    }    public static List<Map<String, Object>> createJsonToListMap(            String jsonString) {        List<Map<String, Object>> list2 = JSON.parseObject(jsonString,                new TypeReference<List<Map<String, Object>>>() {                });        return list2;    }    public static void main(String[] args) {        // TODO Auto-generated method stub        // Person person1 = new Person("张三1", 24, "北京1");        // Person person2 = new Person("张三2", 23, "北京2");        // List<Person> list = new ArrayList<Person>();        // list.add(person1);        // list.add(person2);        List<Map<String, Object>> list = new ArrayList<Map<String, Object>>();        Map<String, Object> map = new HashMap<String, Object>();        map.put("name", "jack");        map.put("age", 23);        Map<String, Object> map2 = new HashMap<String, Object>();        map2.put("name", "rose");        map2.put("age", 24);        list.add(map);        list.add(map2);        String jsonString = JSON.toJSONString(list);        System.out.println(jsonString);        // JSON.parseArray(arg0, arg1)        List<Map<String, Object>> list2 = JSON.parseObject(jsonString,                new TypeReference<List<Map<String, Object>>>() {                });        // List<Person> lists = JSON.parseArray(arg0, arg1);        System.out.println(list2.toString());    }}

·四、JDBC框架介绍

·JDBC程序访问数据库的步骤

·Ø步骤一：加载JDBC驱动程序

·Ø步骤二：提供连接参数

·Ø步骤三：建立一个数据库的连接

·Ø步骤四：创建一个statement

·Ø步骤五：执行SQL语句

·Ø步骤六：处理结果

·Ø步骤七：关闭JDBC对象

·JDBC代码范例

·1.定义基类：UserInfo.java

package com.jdbc.dbutils.domain;import java.io.Serializable;public class UserInfo implements Serializable {    private static final long serialVersionUID = 1L;    private int id;    private String username;    private String pswd;    @Override    public String toString() {        return "UserInfo [id=" + id + ", username=" + username + ", pswd="                + pswd + "]";    }    public int getId() {        return id;    }    public void setId(int id) {        this.id = id;    }    public String getUsername() {        return username;    }    public void setUsername(String username) {        this.username = username;    }    public String getPswd() {        return pswd;    }    public void setPswd(String pswd) {        this.pswd = pswd;    }    public static long getSerialversionuid() {        return serialVersionUID;    }    public UserInfo() {        // TODO Auto-generated constructor stub    }}

·2.建立JdbcUtils.java类

package com.jdbc.dbutils;import java.lang.reflect.Field;import java.sql.Connection;import java.sql.DriverManager;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.sql.ResultSetMetaData;import java.sql.SQLException;import java.util.ArrayList;import java.util.HashMap;import java.util.List;import java.util.Map;import com.jdbc.dbutils.domain.UserInfo;public class JdbcUtils {    // 表示定义数据库的用户名    private final String USERNAME = "root";    // 定义数据库的密码    private final String PASSWORD = "admin";    // 定义数据库的驱动信息    private final String DRIVER = "com.mysql.jdbc.Driver";    // 定义访问数据库的地址    private final String URL = "jdbc:mysql://localhost:3306/mydb";    // 定义数据库的链接    private Connection connection;    // 定义sql语句的执行对象    private PreparedStatement pstmt;    // 定义查询返回的结果集合    private ResultSet resultSet;    public JdbcUtils() {        try {            Class.forName(DRIVER);            System.out.println("注册驱动成功!!");        } catch (Exception e) {            // TODO: handle exception        }    }    // 定义获得数据库的链接    public Connection getConnection() {        try {            connection = DriverManager.getConnection(URL, USERNAME, PASSWORD);        } catch (Exception e) {            // TODO: handle exception        }        return connection;    }    /**     * 完成对数据库的表的添加删除和修改的操作     *      * @param sql     * @param params     * @return     * @throws SQLException     */    public boolean updateByPreparedStatement(String sql, List<Object> params)            throws SQLException {        boolean flag = false;        int result = -1;// 表示当用户执行添加删除和修改的时候所影响数据库的行数        pstmt = connection.prepareStatement(sql);        int index = 1;        if (params != null && !params.isEmpty()) {            for (int i = 0; i < params.size(); i++) {                pstmt.setObject(index++, params.get(i));            }        }        result = pstmt.executeUpdate();        flag = result > 0 ? true : false;        return flag;    }    /**     * 查询返回单条记录     *      * @param sql     * @param params     * @return     * @throws SQLException     */    public Map<String, Object> findSimpleResult(String sql, List<Object> params)            throws SQLException {        Map<String, Object> map = new HashMap<String, Object>();        int index = 1;        pstmt = connection.prepareStatement(sql);        if (params != null && !params.isEmpty()) {            for (int i = 0; i < params.size(); i++) {                pstmt.setObject(index++, params.get(i));            }        }        resultSet = pstmt.executeQuery();// 返回查询结果        ResultSetMetaData metaData = resultSet.getMetaData();        int col_len = metaData.getColumnCount();// 获得列的名称        while (resultSet.next()) {            for (int i = 0; i < col_len; i++) {                String cols_name = metaData.getColumnName(i + 1);                Object cols_value = resultSet.getObject(cols_name);                if (cols_value == null) {                    cols_value = "";                }                map.put(cols_name, cols_value);            }        }        return map;    }    /**     * 查询返回多行记录     *      * @param sql     * @param params     * @return     * @throws SQLException     */    public List<Map<String, Object>> findMoreResult(String sql,            List<Object> params) throws SQLException {        List<Map<String, Object>> list = new ArrayList<Map<String, Object>>();        int index = 1;        pstmt = connection.prepareStatement(sql);        if (params != null && !params.isEmpty()) {            for (int i = 0; i < params.size(); i++) {                pstmt.setObject(index++, params.get(i));            }        }        resultSet = pstmt.executeQuery();        ResultSetMetaData metaData = resultSet.getMetaData();        int cols_len = metaData.getColumnCount();        while (resultSet.next()) {            Map<String, Object> map = new HashMap<String, Object>();            for (int i = 0; i < cols_len; i++) {                String cols_name = metaData.getColumnName(i + 1);                Object cols_value = resultSet.getObject(cols_name);                if (cols_value == null) {                    cols_value = "";                }                map.put(cols_name, cols_value);            }            list.add(map);        }        return list;    }    // jdbc的封装可以用反射机制来封装：    public <T> T findSimpleRefResult(String sql, List<Object> params,            Class<T> cls) throws Exception {        T resultObject = null;        int index = 1;        pstmt = connection.prepareStatement(sql);        if (params != null && !params.isEmpty()) {            for (int i = 0; i < params.size(); i++) {                pstmt.setObject(index++, params.get(i));            }        }        resultSet = pstmt.executeQuery();        ResultSetMetaData metaData = resultSet.getMetaData();        int cols_len = metaData.getColumnCount();        while (resultSet.next()) {            // 通过反射机制创建实例            resultObject = cls.newInstance();            for (int i = 0; i < cols_len; i++) {                String cols_name = metaData.getColumnName(i + 1);                Object cols_value = resultSet.getObject(cols_name);                if (cols_value == null) {                    cols_value = "";                }                Field field = cls.getDeclaredField(cols_name);                field.setAccessible(true);// 打开javabean的访问private权限                field.set(resultObject, cols_value);            }        }        return resultObject;    }    /**     * 通过反射机制访问数据库     *      * @param <T>     * @param sql     * @param params     * @param cls     * @return     * @throws Exception     */    public <T> List<T> findMoreRefResult(String sql, List<Object> params,            Class<T> cls) throws Exception {        List<T> list = new ArrayList<T>();        int index = 1;        pstmt = connection.prepareStatement(sql);        if (params != null && !params.isEmpty()) {            for (int i = 0; i < params.size(); i++) {                pstmt.setObject(index++, params.get(i));            }        }        resultSet = pstmt.executeQuery();        ResultSetMetaData metaData = resultSet.getMetaData();        int cols_len = metaData.getColumnCount();        while (resultSet.next()) {            T resultObject = cls.newInstance();            for (int i = 0; i < cols_len; i++) {                String cols_name = metaData.getColumnName(i + 1);                Object cols_value = resultSet.getObject(cols_name);                if (cols_value == null) {                    cols_value = "";                }                Field field = cls.getDeclaredField(cols_name);                field.setAccessible(true);                field.set(resultObject, cols_value);            }            list.add(resultObject);        }        return list;    }    public void releaseConn() {        if (resultSet != null) {            try {                resultSet.close();            } catch (SQLException e) {                // TODO Auto-generated catch block                e.printStackTrace();            }        }        if (pstmt != null) {            try {                pstmt.close();            } catch (SQLException e) {                // TODO Auto-generated catch block                e.printStackTrace();            }        }        if (connection != null) {            try {                connection.close();            } catch (SQLException e) {                // TODO Auto-generated catch block                e.printStackTrace();            }        }    }    /**     * @param args     */    public static void main(String[] args) {        // TODO Auto-generated method stub        JdbcUtils jdbcUtils = new JdbcUtils();        jdbcUtils.getConnection();        // String sql = "insert into userinfo(username,pswd) values(?,?)";        // List<Object> params = new ArrayList<Object>();        // params.add("rose");        // params.add("123");        // try {        // boolean flag = jdbcUtils.updateByPreparedStatement(sql, params);        // System.out.println(flag);        // } catch (SQLException e) {        // // TODO Auto-generated catch block        // e.printStackTrace();        // }        String sql = "select * from userinfo ";//      List<Object> params = new ArrayList<Object>();//      params.add(1);        try {            List<UserInfo> list = jdbcUtils.findMoreRefResult(sql,                    null, UserInfo.class);            System.out.println(list);        } catch (Exception e) {            // TODO: handle exception        } finally {            jdbcUtils.releaseConn();        }    }}

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