Mybatis

Maven环境下的Mybatis-HelloWorld

（单独学mybatis参考：http://www.mybatis.org/mybatis-3/zh/index.html ，学spring与mybatis：http://www.mybatis.org/spring/zh/index.html）

1.首先，新建Maven工程，在pom.xml文件中添加依赖（mybatis，mysql，junit...暂时只用这么多）

　　

<project xmlns="http://maven.apache.org/POM/4.0.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>mybatis3</groupId>
    <artifactId>com</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <dependencies>
        <!-- mybatis依赖 -->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.2</version>
        </dependency>
        <!-- mysql连接依赖 -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.47</version>
        </dependency>
        <!-- junit单元测试 -->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>
    </dependencies>
</project>

2.准备mybatis配置文件，mybatis-config.xml，在mybatis中文网上拷贝

　　

<?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="123456" />
			</dataSource>
		</environment>
	</environments>
	<mappers>
		<mapper resource="BlogMapper.xml" />
	</mappers>
</configuration>

　　

3.写bean与Mapper

　　

package com.entity;

public class Blog {
	private Integer id;
	private String name;
	public Integer getId() {
		return id;
	}
	public void setId(Integer id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public Blog() {
	}
	public Blog(Integer id, String name) {
		this.id = id;
		this.name = name;
	}
	@Override
	public String toString() {
		return "Blog [id=" + id + ", name=" + name + "]";
	}

}

　　

package com.mapper;

import com.entity.Blog;

public interface BlogMapper {
	public Blog selectBlog(Integer id);
}


<?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.mapper.BlogMapper">
  <select id="selectBlog" resultType="com.entity.Blog">
    select * from blog where id = #{id}
  </select>
</mapper>

　　

4.写测试类进行测试

　　

package com.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.entity.Blog;
import com.mapper.BlogMapper;

public class BlogTest {
	private SqlSessionFactory getSqlSessionFactory() throws IOException {
		InputStream inputStream = Resources.getResourceAsStream("mybatis-config.xml");
		SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
		return sqlSessionFactory;
	}
	@Test
	public void test() throws Exception {
		SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
		SqlSession openSession = sqlSessionFactory.openSession();
		try {
			BlogMapper mapper = openSession.getMapper(BlogMapper.class);
			Blog blog = mapper.selectBlog(1);
			System.out.println(blog);
		} finally {
			openSession.close();
		}
	}
}

　　需提前准备Mysql数据库，Bolg表（id，name）两个字段

　　遇到的问题：

　　　　1.找不到mybatis-config配置文件

　　　　   解决办法，将配置文件放在/com/src/main/resources目录下，访问时，直接给名称即可

　　　　2.BlogMapper.xml文件放在com.mapper下得不到加载，找不到mapper.xml文件问题

　　　　  解决办法，将配置文件放在/com/src/main/resources目录下，访问时，直接给名称即可

　　　　3.mapper.xml文件的命名空间名称与mapper.java文件包名不匹配（Type interface com.mapper.XMapper is not known to the MapperRegistry）问题

　　　　  解决方法，将mapper.xml的namespace属性值写成与之对应的mapper.java文件的所在包名即可