Mybatis_01_HelloWorld

項目概述

這個項目是按照Mybatis的官方文檔來實現的一個簡單的連接數據庫並查詢數據的一個項目，主要的目的是要來練習和入門Mybatis

先來看一下運行結果

DEBUG 11-13 11:01:59,469 ==> Preparing: select id,last_name lastname,email,gender from tbl_employee where id=? (BaseJdbcLogger.java:145)
DEBUG 11-13 11:01:59,664 ==> Parameters: 1(Integer) (BaseJdbcLogger.java:145)
DEBUG 11-13 11:01:59,758 <== Total: 1 (BaseJdbcLogger.java:145)
class com.sun.proxy.$Proxy4
Employee [id=1, lastName=Tom, [email protected], gender=0]

目錄結構

lib包裏面有log4.jar,mybatis-3.4.1.jar,mysql-connector-java-5.1.3.jar

一.數據庫的創建（自己在裏面添加數據）

CREATE TABLE `tbl_employee` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `last_name` varchar(255) DEFAULT NULL,
  `gender` char(1) DEFAULT NULL,
  `email` varchar(255) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=gbk

二.配置mybatis-config.xml的全局配置文件和EmployeeMapper.xml

 mybatis-config.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration
 PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
 "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC" />
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver" />
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis" />
                <property name="username" value="root" />
                <property name="password" value="628081" />
            </dataSource>
        </environment>
    </environments>
    
    <!-- 将我们写好的sql映射文件（EmployeeMapper.xml）一定要注册到全局配置文件（mybatis-config.xml）中 -->
    <mappers>
        <mapper resource="EmployeeMapper.xml" />
    </mappers>
</configuration>

EmployeeMapper.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper
 PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
 "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.yuyi.mybatis.dao.EmployeeMapper">
<!-- 
namespace:名称空间;指定为接口的全类名
id：唯一标识
resultType：返回值类型
#{id}：从传递过来的参数中取出id值

public Employee getEmpById(Integer id);
 -->
    
    <select id="selectEmp" resultType="com.yuyi.mybatis.beans.Employee">
      select id,last_name lastname,email,gender  from tbl_employee where id=#{id}
    </select>
    
    <select id="getEmpById" resultType="com.yuyi.mybatis.beans.Employee">
     select id,last_name lastname,email,gender  from tbl_employee where id=#{id}
    </select>
</mapper>

log4j.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
 
<log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/">
 
 <appender name="STDOUT" class="org.apache.log4j.ConsoleAppender">
   <param name="Encoding" value="UTF-8" />
   <layout class="org.apache.log4j.PatternLayout">
    <param name="ConversionPattern" value="%-5p %d{MM-dd HH:mm:ss,SSS} %m  (%F:%L) \n" />
   </layout>
 </appender>
 <logger name="java.sql">
   <level value="debug" />
 </logger>
 <logger name="org.apache.ibatis">
   <level value="info" />
 </logger>
 <root>
   <level value="debug" />
   <appender-ref ref="STDOUT" />
 </root>
</log4j:configuration>

三.創建實體類，接口和測試方法

Employee.java(這裏要注意的是實體類的字段必須與數據庫相對應)

package com.yuyi.mybatis.beans;

public class Employee {

    private Integer id;
    private String lastName;
    private String email;
    private String gender;
    
    public Integer getId() {
        return id;
    }
    
    public void setId(Integer id) {
        this.id = id;
    }
    
    public String getLastName() {
        return lastName;
    }
    
    public void setLastName(String lastName) {
        this.lastName = lastName;
    }
    
    public String getEmail() {
        return email;
    }
    
    public void setEmail(String email) {
        this.email = email;
    }
    
    public String getGender() {
        return gender;
    }
    
    public void setGender(String gender) {
        this.gender = gender;
    }
    
    @Override
    public String toString() {
        return "Employee [id=" + id + ", lastName=" + lastName + ", email=" + email + ", gender=" + gender + "]";
    }
    
    
}

EmployeeMapper.java（接口：裏面有方法）

package com.yuyi.mybatis.dao;

import com.yuyi.mybatis.beans.Employee;

public interface EmployeeMapper {

    public Employee getEmpById(Integer id);
}

MybatisTest.java

package com.yuyi.mybatis.test;

import java.io.IOException;
import java.io.InputStream;

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 com.yuyi.mybatis.beans.Employee;
import com.yuyi.mybatis.dao.EmployeeMapper;

public class MyBatisTest {

    public SqlSessionFactory getSqlSessionFactory() throws IOException {
        String resource = "mybatis-config.xml";
        InputStream iStream = Resources.getResourceAsStream(resource);
        return new SqlSessionFactoryBuilder().build(iStream);
    }

//    @Test
//    public void test() throws IOException {
//        SqlSessionFactory sessionFactory=getSqlSessionFactory();
//        SqlSession openSession=sessionFactory.openSession();
//
//        try {
//            Employee employee=openSession.selectOne("selectEmp",1);
//            System.out.println(employee);
//        } catch (Exception e) {
//            e.printStackTrace();
//        }finally {
//            openSession.close();
//        }
//    }
    @Test
    public void test01() throws IOException {
        // 1.获取SqlSessionFactory对象
        SqlSessionFactory sessionFactory = getSqlSessionFactory();
        // 2.获取SqlSession对象
        SqlSession openSession = sessionFactory.openSession();
        try {
            // 3、获取接口的实现类对象
            // 会为接口自动的创建一个代理对象，代理对象去执行增删改查方法
            EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
            Employee employee = mapper.getEmpById(1);
            System.out.println(mapper.getClass());
            System.out.println(employee);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            openSession.close();
        }
    }
}