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MyBatis上手入门实例

MyBatis下载、配置及测试

点击下载
MyBatis在线中文文档
下载之后打开,如图:
这里写图片描述
第一个使我们需要用到的包,pdf文档是MyBatis英文手册,后面两个分别是javadoc文档和源码。
在这里我们还需要导入MySQL数据库驱动jar包。官方驱动jar包下载地址
这些准备以后,我们开始配置。
1. 打开MyEclipse,导入jar包。在src下新建一个包,并新建配置文件conf.xml。如图:
这里写图片描述

2. 新建测试数据库mybatis,并新建两条数据。

![这里写图片描述](http://img.blog.csdn.net/20160413165119517)
  1. 在Mybatis中定义Mapper信息有两种方式,一种是利用xml写一个对应的包含Mapper信息的配置文件;另一种就是定义一个Mapper接口,然后定义一些相应的操作方法,再辅以相应的操作注解。conf.xml代码,具体参数的解释请看文档。
<?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="root" />
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="com/MyBatis/test1/userMapper.xml"/>
        <mapper class="com.MyBatis.test1.UserMapper1"/>
    </mappers>
</configuration>

4.新建一个实体类User。

package com.MyBatis.test1;

public class User {
    private int id;
    private String name;
    private int age;

    public User() {
        super();
    }
    public User(int id, String name, int age) {
        super();
        this.id = id;
        this.name = name;
        this.age = age;
    }
    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 int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    @Override
    public String toString() {
        return "User [id=" + id + ", name=" + name + ", age=" + age + "]";
    }
}

5.新建userMapper.xml文件,文件参数解释请看文档,代码如下:

<?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.MyBatis.test1.userMapper">
    <select id="getUser" parameterType="int"
        resultType="com.MyBatis.test1.User">
        select * from users where id=#{id}
    </select>
    <select id = "insertUser" parameterType="com.MyBatis.test1.User">
        insert into users(name,age) values(#{name},#{age});
    </select>
    <delete id="deleteUser" parameterType="int">
        delete from users where id=#{id};
    </delete>

    <update id="updateUser" parameterType="com.MyBatis.test1.User">
        update users set name =#{name},age=#{age} where id = #{id};
    </update>

    <select id="selectAllUsers" resultType="com.MyBatis.test1.User">
        select * from users;
    </select>
</mapper>

6.新建 测试类test,此处采用JUnit4测试,然后逐个方法进行测试。

package com.MyBatis.test1;

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

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

public class Test1 {

    String resource = "conf.xml";
    InputStream is = Test1.class.getClassLoader().getResourceAsStream(resource);
    SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(is);
    SqlSession session = factory.openSession(true);
    UserMapper1 mapper = session.getMapper(UserMapper1.class);

    @Test
    public void insert() {
        User user = new User();
        user.setName("dudefu");
        user.setAge(20);
        String statementInsert = "com.MyBatis.test1.userMapper.insertUser";
        session.insert(statementInsert, user);

    }

    public void update() {
        User user = new User();
        user.setName("ddf");
        user.setAge(20);
        user.setId(6);
        String statement = "com.MyBatis.test1.userMapper.updateUser";
        session.update(statement, user);
    }

    public void selectAllUsers() {
        String statementSelectAll = "com.MyBatis.test1.userMapper.selectAllUsers";
        List<User> selectAllUser = session.selectList(statementSelectAll);
        System.out.println(selectAllUser);
    }

    public void delete() {
        String statement = "com.MyBatis.test1.userMapper.deleteUser";
        int a = session.delete(statement, 10);
        System.out.println(a);
    }
}

7.采用注解的方式。首先新建接口类userMapper1,此处注意,如果接口类和userMpper.xml在同一个包内,则接口类的名字不能和userMapper.xml的名字相同,否则会报错
java.lang.NoClassDefFoundError: com/MyBatis/test1/userMapper (wrong name: com/MyBatis/test1/UserMapper
具体原因,启动程序后,程序首先会加载所有文件,这时userMpper.class和userMpper.xml会发生冲突。所以如果在同一个包内需改名,此处改名为userMapper1.class。userMapper1.class代码如下:

package com.MyBatis.test1;

import java.util.List;
import org.apache.ibatis.annotations.Delete;
import org.apache.ibatis.annotations.Insert;
import org.apache.ibatis.annotations.Select;
import org.apache.ibatis.annotations.Update;

public interface UserMapper1 {

    @Insert("insert into users(name,age) values(#{name},#{age})")
    public int insertUser(User user);

    @Delete("delete from users where id=#{id}")
    public int deleteUserById(int id);

    @Update("update users set name =#{name},age=#{age} where id = #{id}")
    public int updateUser(User user);

    @Select("select * from users where id=#{id}")
    public User getUserById(int id);

    @Select("select * from users")
    public List<User>  getAllUser();
}

8.新建测试类test2。代码如下:

package com.MyBatis.test2;

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

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

public class Test2 {

    String resource = "conf.xml";
    InputStream is = Test1.class.getClassLoader().getResourceAsStream(resource);
    SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(is);
    SqlSession session = factory.openSession(true);
    UserMapper1 mapper = session.getMapper(UserMapper1.class);

    public void testInsert(){
        int insert = mapper.insertUser(new User(-1,"dudefu",23));
        System.out.println(insert);
    }

    public void testUpdate(){
        int update = mapper.updateUser(new User(11,"ddf",34));
        System.out.println(update);
    }

    public void testdelete(){
        int delete = mapper.deleteUserById(11);
        System.out.println(delete);
    }
    @Test
    public void selectAllUser(){
        List<User> selectAllUsers = mapper.getAllUser();
        System.out.println(selectAllUsers);
    }
}

按照以上步骤进行操作,测试应该是不报错的。如果出错了,一般出错在 conf.xml中的路径配置,如下段代码;

<mappers>
        <mapper resource="com/MyBatis/test1/userMapper.xml"/>
        <mapper class="com.MyBatis.test1.UserMapper1"/>
    </mappers>

和userMapper.xml中。

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