Mybatis系列（二）Mybatis-HelloWorld

Mybatis系列（二）Mybatis-HelloWorld

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一、Mybatis环境搭建及简单实例

1.1、引入依赖

新建java项目， 添加依赖包：mybatis包、数据库驱动包(mysql-connection)、日志包(log4j)， 如果是maven项目， 那么添加依赖包就简单了，直接在pom.xml添加依赖即可，如下：

<dependencies>
      
    <dependency>
      <groupId>junitgroupId>
      <artifactId>junitartifactId>
      <version>4.11version>
      <scope>testscope>
    dependency>
    
    
    <dependency>
        <groupId>log4jgroupId>
      <artifactId>log4jartifactId>
        <version>1.2.16version>
    dependency>
    
    
    <dependency>
        <groupId>org.mybatisgroupId>
      <artifactId>mybatisartifactId>
        <version>3.2.6version>
    dependency>
    
    
    <dependency>
        <groupId>mysqlgroupId>
        <artifactId>mysql-connector-javaartifactId>
        <version>5.1.12version>
    dependency>
  dependencies>

如果是传统java项目,则添加以下jar包即可,我这里的测试用例是非maven项目:
mybatis-x.x.x.jar
log4j.jar
mysql-connector-java-5.1.37-bin.jar
具体的jar包可到以下地址搜索下载:https://mvnrepository.com/

1.2、配置log4j.xml以及Mybatis的全局配置文件

在类路径(项目的src路径下)建立log4j.xml，然后建立一个mybatis-config.xml文件，其中mybatis-config.xml指导着mybatis整个的运行流程,配置如下：
项目结构:

log4j.xml:

<log4j:configuration>

 <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="debug" />
 logger>
 <root>
   <level value="debug" />
   <appender-ref ref="STDOUT" />
 root>
log4j:configuration>

mybatis-config.xml:

<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="root"/>
            dataSource>
        environment>
    environments>
    
    <mappers>
        <mapper resource="mapper/Employee.xml"/>
    mappers>
configuration>

1.3、helloworld编写

sql:

USE `mybatis`;

/*Table structure for table `t_employee` */

DROP TABLE IF EXISTS `t_employee`;

CREATE TABLE `t_employee` (
  `id` INT(20) NOT NULL AUTO_INCREMENT,
  `empName` VARCHAR(30) DEFAULT NULL,
  `email` VARCHAR(30) DEFAULT NULL,
  `gender` INT(20) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=INNODB AUTO_INCREMENT=8 DEFAULT CHARSET=utf8;

/*Data for the table `t_employee` */

INSERT  INTO `t_employee`(`id`,`empName`,`email`,`gender`) VALUES (1,'wangwu','[email protected]',1);

/*!40101 SET SQL_MODE=@OLD_SQL_MODE */;
/*!40014 SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS */;
/*!40014 SET UNIQUE_CHECKS=@OLD_UNIQUE_CHECKS */;
/*!40111 SET SQL_NOTES=@OLD_SQL_NOTES */;

javaBean:

package com.cetc.bean;

public class Employee {
     
    private Integer id;
    private String empName;
    private String email;
    private Integer gender;
    ...
    省略构造器、toString()、Getter、Setter方法
}

EmployeeDao:

package com.cetc.dao;

import com.cetc.bean.Employee;

public interface EmployeeDao {
     
    Employee getEmployeeByID(Integer id);

    int insertEmployee(Employee employee);

    boolean updateEmployee(Employee employee);

    int deleteEmployee(Integer id);
}

Employee.xml:

<mapper namespace="com.cetc.dao.EmployeeDao">

    <select id="getEmployeeByID" resultType="com.cetc.bean.Employee">
        select * from t_employee where id = #{id}
    select>

    <insert id="insertEmployee">
        INSERT INTO
            t_employee(empName , email , gender)
        VALUES (#{empName} , #{email} , #{gender})
    insert>

    <update id="updateEmployee">
        UPDATE t_employee
        SET empName = #{empName} , email = #{email} , gender = #{gender}
        WHERE id = #{id}
    update>

    <delete id="deleteEmployee">
        DELETE FROM t_employee WHERE id = #{id}
    delete>


mapper>

测试类:

package com.cetc;

import com.cetc.bean.Employee;
import com.cetc.dao.EmployeeDao;
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.Before;
import org.junit.Test;

import java.io.InputStream;

public class MybatisCrudTest {
     
    private SqlSessionFactory sqlSessionFactory = null;

    @Before
    public void SqlSessionFactory() throws Exception {
     
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    }

    @Test
    public void testMybatisSelect(){
     
        //获取与数据库的一次会话
        SqlSession sqlSession = sqlSessionFactory.openSession();
        try {
     
            EmployeeDao employeeDao = sqlSession.getMapper(EmployeeDao.class);
            Employee employee = employeeDao.getEmployeeByID(1);
            System.out.println("查询到的员工为:" + employee);
        }finally {
     
            sqlSession.close();
        }
    }

    @Test
    public void testMybatisInsert(){
     
        //获取与数据库的一次会话，注意获取sqlsession时设置为true是为了设置事务为自动提交
        SqlSession sqlSession = sqlSessionFactory.openSession(true);
        try {
     
            EmployeeDao employeeDao = sqlSession.getMapper(EmployeeDao.class);
            int i = employeeDao.insertEmployee(new Employee(null, "lisi", "[email protected]", 2));
            System.out.println("成功增加了"+i+"条");
        }finally {
     
            sqlSession.close();
        }
    }

    @Test
    public void testMybatisUpdate(){
     
        //获取与数据库的一次会话，注意获取sqlsession时设置为true是为了设置事务为自动提交
        SqlSession sqlSession = sqlSessionFactory.openSession(true);
        try {
     
            EmployeeDao employeeDao = sqlSession.getMapper(EmployeeDao.class);
            boolean flag = employeeDao.updateEmployee(new Employee(1, "wangwu", "[email protected]", 1));
            if (flag){
     
                System.out.println("修改成功");
            }else {
     
                System.out.println("修改失败");
            }
        }finally {
     
            sqlSession.close();
        }
    }

    @Test
    public void testMybatisDelete(){
     
        //获取与数据库的一次会话，注意获取sqlsession时设置为true是为了设置事务为自动提交
        SqlSession sqlSession = sqlSessionFactory.openSession(true);
        try {
     
            EmployeeDao employeeDao = sqlSession.getMapper(EmployeeDao.class);
            int i = employeeDao.deleteEmployee(1);
            System.out.println("成功删除了"+i+"条");
        }finally {
     
            sqlSession.close();
        }
    }
}

二、HelloWorld细节

两个配置文件:

1. 全局配置文件:mybatis-config用来指导mybatis正确运行的一些全局配置
2. SQL映射文件:EmployeeDao.xml相当于对dao接口的一个实现描述

//其中employee 为代理对象,类型为class com.sun.proxy.$Proxy5
EmployeeDao employeeDao = sqlSession.getMapper(EmployeeDao.class);
System.out.println(employeeDao.getClass());

SqlSessionFactory与SqlSession：

1. SqlSessionFactory创建sqlsession,工厂只new一次就可以了
2. Sqlsession相当于connection与数据库进行连接,和数据库的一次会话,每次与数据库交互都应该获取一次sqlsession

三、总结

此篇文章书写了一个关于mybatis的入门案例,个人建议学习此系列后面的章节前最好按照此篇的案例练习一遍。下面附上源码下载地址:源码下载