MyBatis-User例子

1、在mysql中执行下面的sql

CREATE DATABASE mybatisdb;
USE mybatisdb;
CREATE TABLE USER(id INT PRIMARY KEY AUTO_INCREMENT,NAME VARCHAR(100),addr VARCHAR(100),age INT);
INSERT INTO USER VALUES(NULL,'张三','北京',28);
INSERT INTO USER VALUES(NULL,'李四','上海',30);
INSERT INTO USER VALUES(NULL,'王五','广州',19);

2、创建一个普通的java工程，引入jar包

在项目上右键，创建一个文件夹起名为lib

把jar包复制粘贴到项目目录下

右键BuildPath ->Add to Build Path

3、创建pojo包，在包下创建User类

User 类的代码如下

package pojo;

/**
 * 这个类用来和User表做映射关系 要求：属性名必须和表字段名保持一致
 */
public class User {
    // id
    private int id;

    // 用户名
    private String name;

    // 地址
    private String addr;

    // 年龄
    private int age;

    // getter setter
    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getAddr() {
        return addr;
    }

    public void setAddr(String addr) {
        this.addr = addr;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    @Override
    public String toString() {
        return "User [id=" + id + ", name=" + name + ", addr=" + addr + ", age=" + age + "]";
    }
}

4在pojo包下，创建UserMapper.xml

/mybatis1/src/pojo/UserMapper.xml

UserMapper.xml的代码如下

5在src目录下创建sqlMapConfig.xml

/mybatis1/src/sqlMapConfig.xml

sqlMapConfig.xml代码如下(是mapper仓库)

6在src下创建空白文件，名称为log4j.properties

在文件内输入如下内容后保存

# Global logging configuration
log4j.rootLogger=DEBUG, stdout
# Console output...
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%5p [%t] - %m%n

7在src下创建test包，在包下创建TestUser测试类

TestUser

package test;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Test;

import pojo.User;

/*
 * 测试User是否能成功查询
 */
public class TestUser {
    @Test
    public void testUserQuery() throws IOException{
        //1.创建会话工厂
        InputStream in=Resources.getResourceAsStream("sqlMapConfig.xml");
        SqlSessionFactory ssf=new SqlSessionFactoryBuilder().build(in);
        //2.创建Sqlsession，执行sql
        SqlSession session = ssf.openSession();
        //参数为定位sql的位置namespace值.id值
        List list = session.selectList("userns.all");
        //3.处理结果
        for (User user : list) {
            System.out.println(user);
        }
        //4.释放资源
        session.close();
    }
}

8双击选中testUserQuery方法，右键RunAs ->JUnit Test

进度条变绿，控制台正常输出数据库表内容表示成功

控制台内容如下

DEBUG [main] - Logging initialized using 'class org.apache.ibatis.logging.log4j.Log4jImpl' adapter.
DEBUG [main] - PooledDataSource forcefully closed/removed all connections.
DEBUG [main] - PooledDataSource forcefully closed/removed all connections.
DEBUG [main] - PooledDataSource forcefully closed/removed all connections.
DEBUG [main] - PooledDataSource forcefully closed/removed all connections.
DEBUG [main] - Opening JDBC Connection
DEBUG [main] - Created connection 119981396.
DEBUG [main] - ooo Using Connection [com.mysql.jdbc.JDBC4Connection@726c554]
DEBUG [main] - ==>  Preparing: select * from user 
DEBUG [main] - ==> Parameters: 
User [id=1, name=张三, addr=北京, age=28]
User [id=2, name=李四, addr=上海, age=30]
User [id=3, name=王五, addr=广州, age=19]
DEBUG [main] - Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@726c554]
DEBUG [main] - Closing JDBC Connection [com.mysql.jdbc.JDBC4Connection@726c554]
DEBUG [main] - Returned connection 119981396 to pool.

可发现底层其实是jdbc和连接池操作，最后一句话是归还连接池