import com.google.gson.Gson;
import com.google.gson.reflect.TypeToken;
import java.sql.*;
import java.util.*;
public class Main {
public static void main(String[] args) {
Connection conn = null;
User user = null;
Gson gson = new Gson();
try {
# JDK6 之前的版本需要加载驱动
# new com.mysql.jdbc.Driver();
# 连接数据库
conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/dbname?" +
"useSSL=false&useUnicode=true&characterEncoding=UTF8", "root", "root");
# 使用 prepareStatement 查询数据库
PreparedStatement preStatement = conn.prepareStatement("select * from tables");
ResultSet res = preStatement.executeQuery();
List<User> users = new ArrayList<User>();
while (res.next()) {
user = new User();
user.setId(Integer.parseInt(res.getString("id")));
user.setUser(res.getString("user"));
users.add(user);
}
# 导出为 json
String strJson = gson.toJson(users);
System.out.println(strJson);
} catch (SQLException e) {
e.printStackTrace();
} finally {
if (conn != null) {
try {
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
}
日度归档:2017-11-07
使用 Gson 序列化 和 反序列化 json
import com.google.gson.Gson;
import com.google.gson.reflect.TypeToken;
public class Main {
public static void main(String[] args) {
User user = new User();
user.setId(1);
user.setUser("admin");
# 实例化 Gson
Gson gson = new Gson();
# 序列化 json
String jsonUser = gson.toJson(user);
System.out.println(jsonUser);
# 反序列化 json
User user1 = gson.fromJson(jsonUser, User.class);
System.out.println(user1);
System.out.println("==============================");
# 列表,使用 List
List<User> users = new ArrayList<>();
for (int i = 0; i < 2; i++) {
users.add(user);
}
String jsonUsers = gson.toJson(users);
System.out.println(jsonUsers);
List<User> users1 = gson.fromJson(jsonUsers, new TypeToken<List<User>>() {
}.getType());
for (User _user : users1) {
System.out.println(_user);
}
System.out.println("==============================");
# 多属性键值对,使用 Map
Map<String, String> ips = new HashMap<>();
for (int i = 0; i < 9; i++) {
ips.put(i + "", "192.168.1.10" + i);
}
String jsonIps = gson.toJson(ips);
System.out.println(jsonIps);
Map<String, String> ips1 = gson.fromJson(jsonIps, new TypeToken<Map<String, String>>() {
}.getType());
Set<String> set = ips1.keySet();
for (String _string : set) {
System.out.println(_string + ":" + ips1.get(_string));
}
}
}