自定义mysql类用于快速执行数据库查询以及将查询结果转为json文件

由于每次连接数据库进行查询比较麻烦，偶尔还需要将查询结果转为json格式的文件，

因此暂时定义一个mysql的类，将这些常用的方法进行封装，便于直接调用（代码如下，个人用，没写什么注释）。

注：导入了https://github.com/stleary/JSON-java的包。

 package connmysql;

 import java.io.IOException;
 import java.io.InputStream;
 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.HashMap;
 import java.util.Map;
 import java.util.Properties;

 import org.json.JSONObject;

 public class MySql {
     /**
      * Define database connection method
      * 1. Calling Connect(String db) for Pass in the database name
      *    that you want to connect to in the MySql.
      * 2. Calling Connect(String db,String sql) for Pass in the
      *    database name that you want to connect to in MySql and
      *    the MySql query command.
      * 3. Calling Close() to close the Database connection.
      * 4. Calling ToJson(String db,String sql) to print a json list.
      * 5. Calling ToJsonObj(String db,String sql) returns a json object
      */

     //Defining database connection parameters
     public static final String url = "jdbc:mysql://localhost:3306/";
     public static final Properties properties = new Properties();
     public Connection conn = null;
     public PreparedStatement ppst = null;
     public JSONObject json = null;
     //Defining database connection methods
         public void Connect(String db) {
             try {
                 InputStream input = MySql.class.getClassLoader().getResourceAsStream("connect.properties");
                 properties.load(input);
                 //New version driver name:com.mysql.cj.jdbc.Driver
                 //Old version driver name:com.mysql.jdbc.Driver
                 Class.forName("com.mysql.cj.jdbc.Driver");
             } catch (ClassNotFoundException e) {
                 // TODO: handle exception
                 //System.out.println("Driver loading failed");
                 e.printStackTrace();
                 return;
             } catch (IOException e) {
                 //System.out.println("File properties loading failed");
                 // TODO Auto-generated catch block
                 e.printStackTrace();
             }
             db = url+db;
             try {
                 this.conn = DriverManager.getConnection(db, properties);
                 //System.out.println("Successful database connection"+this.conn);
             } catch (SQLException e) {
                 // TODO: handle exception
                 //System.out.println("Failed database connection");
                 e.printStackTrace();
             }
         }

     //Defining database connection methods
     public void Connect(String db,String sql) {
         try {
             InputStream input = MySql.class.getClassLoader().getResourceAsStream("connect.properties");
             properties.load(input);
             Class.forName("com.mysql.cj.jdbc.Driver");
         } catch (ClassNotFoundException e) {
             // TODO: handle exception
             //System.out.println("Driver loading failed");
             e.printStackTrace();
             return;
         } catch (IOException e) {
             //System.out.println("File properties loading failed");
             // TODO Auto-generated catch block
             e.printStackTrace();
         }
         db = url+db;
         try {
             this.conn = DriverManager.getConnection(db, properties);
             this.ppst = this.conn.prepareStatement(sql);
             //System.out.println("Successful database connection"+this.conn);
             //System.out.println("Successful SQL precompiled PreparedStatement"+this.ppst);
         } catch (SQLException e) {
             // TODO: handle exception
             //System.out.println("Failed database connection");
             e.printStackTrace();
         }
     }

     //Close the database connection
     public void Close() {
         try {
             this.conn.close();
             //System.out.println("Successful close database connection");
         } catch (SQLException e) {
             // TODO Auto-generated catch block
             //System.out.println("Failed close database connection");
             e.printStackTrace();
         }
     }
     public void ToJson(String db,String sql) {
         if(!(sql.startsWith("select") || sql.startsWith("SELECT"))) {
             System.out.println("Please pass in a database query statement");
             return;
         }
         MySql mysql = new MySql();
         JSONObject jsonobj = new JSONObject();
         ResultSet result = null;
         try {
             mysql.Connect(db,sql);
             result = mysql.ppst.executeQuery();
             while(result.next()) {
                 ResultSetMetaData rsmd = result.getMetaData();
                 Map<String,String> map = new HashMap<>();
                 for(int i = 1; i <= rsmd.getColumnCount(); i++) {
                     map.put(rsmd.getColumnLabel(i), result.getString(i));
                     jsonobj.put(result.getString("id"), map);
                 }
             }
             System.out.println(jsonobj.toString());
         } catch (SQLException e) {
             // TODO Auto-generated catch block
             e.printStackTrace();
         }
     }

     public JSONObject ToJsonObj(String db,String sql) {
         if(!(sql.startsWith("select") || sql.startsWith("SELECT"))) {
             System.out.println("Please pass in a database query statement");
             return (new JSONObject());
         }
         MySql mysql = new MySql();
         JSONObject jsonobj = new JSONObject();
         ResultSet result = null;
         try {
             mysql.Connect(db,sql);
             result = mysql.ppst.executeQuery();
             while(result.next()) {
                 ResultSetMetaData rsmd = result.getMetaData();
                 Map<String,String> map = new HashMap<>();
                 for(int i = 1; i <= rsmd.getColumnCount(); i++) {
                     map.put(rsmd.getColumnLabel(i), result.getString(i));
                     jsonobj.put(result.getString("id"), map);
                 }
             }
             this.json = jsonobj;
         } catch (SQLException e) {
             // TODO Auto-generated catch block
             e.printStackTrace();
         }
         return this.json;
     }
 }

测试一：

 package test;

 import java.sql.Connection;
 import java.sql.PreparedStatement;
 import java.sql.ResultSet;
 import java.sql.SQLException;

 import connmysql.MySql;

 public class MysqlTest01 {

     public static void main(String[] args) {
         // TODO Auto-generated method stub
         MySql mysql = new MySql();
         try {
             String sql = "INSERT INTO student ( sname, sgender, address ) VALUES ( '孙六', '女', '信阳' )";
             mysql.Connect("testdb",sql);
             Connection conn = mysql.conn;
             PreparedStatement ppst = mysql.ppst;
             System.out.println("Successful database Insert update\t"+ppst.executeUpdate());
             sql = "delete from student where sname='孙六'";
             ppst = conn.prepareStatement(sql);
             System.out.println("Successful database delete update\t"+ppst.executeUpdate());
             sql = "update student set sname=? where sname=?";
             ppst = conn.prepareStatement(sql);
             ppst.setString(1,"张三丰");
             ppst.setString(2,"张三");
             System.out.println("Successful database update\t"+ppst.executeUpdate());
             sql = "select id, sname from student";
             ppst = mysql.conn.prepareStatement(sql);
             ResultSet result=ppst.executeQuery();
             while (result.next()) {
                 System.out.printf("id:%d sanme:%s\n", result.getInt(1),result.getString(2));
             }
             System.out.println("Successful database select");
             mysql.Close();
         } catch (SQLException e) {
             // TODO: handle exception
             e.printStackTrace();
         }
     }
 /*    Successful database connectioncom.mysql.cj.jdbc.ConnectionImpl@13acb0d1
     Successful SQL precompiled PreparedStatementcom.mysql.cj.jdbc.ClientPreparedStatement: INSERT INTO student ( sname, sgender, address ) VALUES ( '孙六', '女', '信阳' )
     Successful database Insert update    1
     Successful database delete update    2
     Successful database update    0
     id:1 sanme:张三丰
     id:2 sanme:李四
     id:3 sanme:王五
     id:5 sanme:张三丰
     id:6 sanme:李四
     id:7 sanme:王五
     Successful database select
     Successful close database connection*/
 }

测试二：

 package test;

 import java.sql.Connection;
 import java.sql.PreparedStatement;
 import java.sql.ResultSet;
 import java.sql.SQLException;

 import connmysql.MySql;

 public class MysqlTest02 {

     public static void main(String[] args) {
         // TODO Auto-generated method stub
         MySql mysql = new MySql();
         try {
             mysql.Connect("testdb","sql");
             Connection conn = mysql.conn;
             String sql = "INSERT INTO student ( sname, sgender, address ) VALUES ( '孙六', '女', '信阳' )";
             PreparedStatement ppst = conn.prepareStatement(sql);
             System.out.println("Successful database Insert update\t"+ppst.executeUpdate());
             sql = "delete from student where sname='孙六'";
             ppst = conn.prepareStatement(sql);
             System.out.println("Successful database delete update\t"+ppst.executeUpdate());
             sql = "update student set sname=? where sname=?";
             ppst = conn.prepareStatement(sql);
             ppst.setString(1,"张三丰");
             ppst.setString(2,"张三");
             System.out.println("Successful database update\t"+ppst.executeUpdate());
             sql = "select id, sname from student";
             ppst = mysql.conn.prepareStatement(sql);
             ResultSet result=ppst.executeQuery();
             while (result.next()) {
                 System.out.printf("id:%d sanme:%s\n", result.getInt(1),result.getString(2));
             }
             System.out.println("Successful database select");
             mysql.Close();
         } catch (SQLException e) {
             // TODO: handle exception
             e.printStackTrace();
         }
     }
 /*    Successful database connectioncom.mysql.cj.jdbc.ConnectionImpl@b62fe6d
     Successful SQL precompiled PreparedStatementcom.mysql.cj.jdbc.ClientPreparedStatement: sql
     Successful database Insert update    1
     Successful database delete update    1
     Successful database update    0
     id:1 sanme:张三丰
     id:2 sanme:李四
     id:3 sanme:王五
     id:5 sanme:张三丰
     id:6 sanme:李四
     id:7 sanme:王五
     Successful database select
     Successful close database connection*/
 }

测试三：

 package test;

 import java.io.File;
 import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.OutputStream;

 import connmysql.MySql;

 public class MysqlTest03 {

     public static void main(String[] args) {
         // TODO Auto-generated method stub
         String sql = "select id, sname from student";
         // 使用一个Stream对象接收成员变量json的String返回即可写入本地文件。
         MySql mysql = new MySql();
         System.out.println("ToJson method print");
         mysql.ToJson("testdb", sql);
         System.out.println("ToJsonObj method print");
         mysql.ToJsonObj("testdb", sql);
         System.out.println(mysql.json.toString());
         File file = new File("TestDir/des.json");
         try {
             if (!file.exists()) {
                 file.createNewFile();
             }
             String str = mysql.json.toString();
             byte[] buffer = str.getBytes();
             OutputStream out = new FileOutputStream(file);
             out.write(buffer, 0, buffer.length);
             System.out.println("Written to local JSON file");
             out.close();
         } catch (IOException e) {
             // TODO Auto-generated catch block
             e.printStackTrace();
         }
     }
 /*    ToJson method print
     {"1":{"sname":"张三丰","id":"1"},"2":{"sname":"李四","id":"2"},"3":{"sname":"王五","id":"3"},"5":{"sname":"张三丰","id":"5"},"6":{"sname":"李四","id":"6"},"7":{"sname":"王五","id":"7"}}
     ToJsonObj method print
     {"1":{"sname":"张三丰","id":"1"},"2":{"sname":"李四","id":"2"},"3":{"sname":"王五","id":"3"},"5":{"sname":"张三丰","id":"5"},"6":{"sname":"李四","id":"6"},"7":{"sname":"王五","id":"7"}}
     Written to local JSON file*/
 }

connect.properties文件：

#Mysql
user=""
password=""
useSSL=false
serverTimezone=UTC
verifyServerCertifate=false

des.json文件：

{"1":{"sname":"张三丰","id":"1"},"2":{"sname":"李四","id":"2"},"3":{"sname":"王五","id":"3"},"5":{"sname":"张三丰","id":"5"},"6":{"sname":"李四","id":"6"},"7":{"sname":"王五","id":"7"}}