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

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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