C3P0数据源的使用(二)

如何通过简便语句实现增删改查？

前提，首先需要创立数据源DataSource得到Connection

c3p0-config.xml(数据库以及连接池配置信息)
在com.util包里面写好C3P0Util.java(通过这个类得到Connection)

以上两个步骤参考上一篇文章URL：
https://blog.csdn.net/weixin_42036647/article/details/82951388

假设有个User类(对应数据库想存的信息)

package com.entity;
import java.util.Date;

public class User {
    private int id;
    private String name;
    private String password;
    private String email;
    private Date birthday;

    //省略一系列的get,set方法
    
    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", password='" + password + '\'' +
                ", email='" + email + '\'' +
                ", birthday=" + birthday +
                '}';
    }
}

TestCRUD.java 增删改一系列操作只需要两句话


QueryRunner qr = new QueryRunner(C3P0Util.getDataSource());

qr.update("insert into users(name,password,email,birthday) values(?,?,?,?)","菜10","123","[email protected]",new Date());
qr.update("update users set name=?,password=? where name=?","周杰杰","333","菜10");
qr.update("delete from users  where name=?","周杰杰");

//批处理，只能执行相同的sql语句
public void testBatch() throws SQLException{
	//创建一个QueryRunner对象
    QueryRunner qr = new QueryRunner(C3P0Util.getDataSource());

    Object[][] params = new Object[10][];//高维代表执行多少次sql语句
    for(int i=0;i<params.length;i++){
    params[i] = new Object[]{"菜10"+i,"123","[email protected]",new Date()};//给每次的sql的？赋值
    }
    qr.batch("insert into users(name,password,email,birthday) values(?,?,?,?)",params);
}

TestSelect.java 查询操作

public void testSelect2() throws SQLException{
    //创建一个QueryRunner 对象
    QueryRunner qr = new QueryRunner(C3P0Util.getDataSource());
    //执行查询语句，并返回结果
    List<User> list = qr.query("select * from users",new BeanListHandler<User>(User.class));

    for(User user : list){
        System.out.println(user);
    }
}

TestResultSetHandler.java 不同取数据的方式

package com.util;

import java.sql.SQLException;
import java.util.List;
import java.util.Map;

import com.entity.User;
import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.ArrayHandler;
import org.apache.commons.dbutils.handlers.ArrayListHandler;
import org.apache.commons.dbutils.handlers.BeanHandler;
import org.apache.commons.dbutils.handlers.BeanListHandler;
import org.apache.commons.dbutils.handlers.ColumnListHandler;
import org.apache.commons.dbutils.handlers.KeyedHandler;
import org.apache.commons.dbutils.handlers.MapHandler;
import org.apache.commons.dbutils.handlers.MapListHandler;
import org.apache.commons.dbutils.handlers.ScalarHandler;


public class TestResultSetHandler {
    //ArrayHandler:适合取1条记录。把该条记录的每列值封装到一个数组中Object[]
    public void tese1() throws SQLException{
        QueryRunner qr = new QueryRunner(C3P0Util.getDataSource());
        Object[] arr  = qr.query("select * from users", new ArrayHandler());

        for (Object o : arr) {
            System.out.println(o);
        }
    }

    //ArrayListHandler:适合取多条记录。把每条记录的每列值封装到一个数组中Object[]，把数组封装到一个List中
    public void tese2() throws SQLException{
        QueryRunner qr = new QueryRunner(C3P0Util.getDataSource());
        List<Object[]> query = qr.query("select * from users", new ArrayListHandler());

        for (Object[] os : query) {
            for (Object o : os) {
                System.out.println(o);
            }
            System.out.println("--------------");
        }
    }

     //ColumnListHandler:取某一列的数据。封装到List中。
    public void tese3() throws SQLException{
        QueryRunner qr = new QueryRunner(C3P0Util.getDataSource());
        List<Object> list = qr.query("select username,password from users", new ColumnListHandler(1));

        for (Object o : list) {
            System.out.println(o);
        }
    }

    //KeyedHandler:取多条记录，每一条记录封装到一个Map中，再把这个Map封装到另外一个Map中，key为指定的字段值。
    public void tese4() throws SQLException{
        QueryRunner qr = new QueryRunner(C3P0Util.getDataSource());
        //大Map的key是表中的某列数据，小Map中的key是表的列名，所以大Map的key是Object类型，小Map的key是String类型
        Map<Object,Map<String,Object>> map = qr.query("select * from users", new KeyedHandler(1));

        for (Map.Entry<Object, Map<String,Object>> m : map.entrySet()) {
            System.out.println(m.getKey());//大Map中key值就是id列的值
            for (Map.Entry<String, Object> mm : m.getValue().entrySet()) {
                System.out.println(mm.getKey()+"\t"+mm.getValue());//取出小Map中的列名和列值
            }
            System.out.println("---------------------");
        }

    }


    //MapHandler:适合取1条记录。把当前记录的列名和列值放到一个Map中
    public void tese5() throws SQLException{
        QueryRunner qr = new QueryRunner(C3P0Util.getDataSource());
        Map<String,Object> map = qr.query("select * from users where id=?", new MapHandler(),20);

        for (Map.Entry<String, Object> m : map.entrySet()) {
            System.out.println(m.getKey()+"\t"+m.getValue());
        }

    }


    //MapListHandler:适合取多条记录。把每条记录封装到一个Map中，再把Map封装到List中
    public void tese6() throws SQLException{
        QueryRunner qr = new QueryRunner(C3P0Util.getDataSource());
        List<Map<String,Object>> list = qr.query("select * from users", new MapListHandler());

        for (Map<String, Object> map : list) {
            for (Map.Entry<String, Object> m : map.entrySet()) {
                System.out.println(m.getKey()+"\t"+m.getValue());
            }
            System.out.println("---------------");
        }
    }

    //ScalarHandler:适合取单行单列数据
    public void tese7() throws SQLException{
        QueryRunner qr = new QueryRunner(C3P0Util.getDataSource());
        Object o = qr.query("select count(*) from users", new ScalarHandler(1));
        System.out.println(o.getClass().getName());
    }

    //BeanHandler:适合取单行单列数据
    public void tese8() throws SQLException{
        QueryRunner qr = new QueryRunner(C3P0Util.getDataSource());
        User user = qr.query("select * from users where id=?", new BeanHandler<User>(User.class),1);
        System.out.println(user);
    }


    //BeanListHandler
    public void tese9() throws SQLException{
        QueryRunner qr = new QueryRunner(C3P0Util.getDataSource());
        List<User> list = qr.query("select * from users where id=?", new BeanListHandler<User>(User.class),1);

        System.out.println(list.size());
    }
}

C3P0数据源的使用(二)

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