MyBatis上手入门实例

MyBatis下载、配置及测试

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MyBatis在线中文文档
下载之后打开，如图：

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：
   

2. 新建测试数据库mybatis，并新建两条数据。

   

3. 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。