1:準備-下載MyBatis源碼:
https://github.com/tuguangquan/mybatis
https://github.com/mybatis/parent
2:idea搭建聚合項目
mybatis繼承parent項目
導入兩個項目,等待兩個項目的pom中的依賴加載完成。
3:寫測試代碼
創建數據庫mybatis與數據庫表role
-- ----------------------------
-- Table structure for role
-- ----------------------------
create database mybatis;
use mybayis;
DROP TABLE IF EXISTS `role`;
CREATE TABLE `role` (
`id` int(11) DEFAULT NULL,
`role_name` varchar(255) DEFAULT NULL,
`note` varchar(255) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
-- ----------------------------
-- Records of role
-- ----------------------------
INSERT INTO `role` VALUES ('1', '張三', '張三的備註');
數據庫表role對應的java實體類role
/*
* @author gethin
* 角色的實體類
*/
public class Role {
private long id;
private String roleName;
private String note;
...
getter setter省略
}
java RoleMapper接口
/*
* @author gethin
*/
public interface RoleMapper {
public Role getRole(Long id);
public Role findRole(String roleName);
public int deleteRole(Long id);
public int insertRole(Role role);
}
RoleMapper
<?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.gethin.mapper.RoleMapper">
<resultMap type="role" id="roleMap">
<id column="id" property="id" javaType="long" jdbcType="BIGINT" />
<result column="role_name" property="roleName" javaType="string"
jdbcType="VARCHAR" />
<result column="note" property="note"
typeHandler="com.gethin.handler.MyStringHandler" />
</resultMap>
<select id="getRole" parameterType="long" resultMap="roleMap">
select
id,role_name as roleName,note from role where id=#{id}
</select>
<select id="findRole" parameterType="long" resultMap="roleMap">
select
id,role_name,note from role where role_name like CONCAT('%',#{roleName
javaType=string,
jdbcType=VARCHAR,typeHandler=com.gethin.handler.MyStringHandler},'%')
</select>
<insert id="insertRole" parameterType="role">
insert into
role(role_name,note) value(#{roleName},#{note})
</insert>
<delete id="deleteRole" parameterType="long">
delete from role where
id=#{id}
</delete>
</mapper>
MyStringHandler
@MappedTypes({String.class})
@MappedJdbcTypes(JdbcType.VARCHAR)
public class MyStringHandler implements TypeHandler<String> {
private Logger log=Logger.getLogger(MyStringHandler.class);
@Override
public String getResult(ResultSet rs, String colName) throws SQLException {
log.info("使用我的TypeHandler,ResultSet列名獲取字符串");
return rs.getString(colName);
}
@Override
public String getResult(ResultSet rs, int index) throws SQLException {
log.info("使用我的TypeHandler,ResultSet下標獲取字符串");
return rs.getString(index);
}
@Override
public String getResult(CallableStatement cs, int index) throws SQLException {
log.info("使用我的TypeHandler,CallableStatement下標獲取字符串");
return cs.getString(index);
}
@Override
public void setParameter(PreparedStatement ps, int index, String value, JdbcType arg3) throws SQLException {
log.info("使用我的TypeHandler");
ps.setString(index, value);
}
}
log4j.properties
log4j.rootLogger=DEBUG,stdout
log4j.logger.org.mybatis=DUBUG
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.logDailyFile.layout.ConversionPattern = %5p %d %C:%m%n
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>
<settings>
<setting name="lazyLoadingEnabled" value="true"/>
<!-- <setting name="aggressiveLazyLoading" value="false"/> -->
</settings>
<typeAliases>
<typeAlias alias="role" type="com.gethin.po.Role"/>
</typeAliases>
<typeHandlers>
<typeHandler jdbcType="VARCHAR" javaType="string" handler="com.gethin.handler.MyStringHandler"/>
</typeHandlers>
<!-- 定義數據庫的信息,默認使用development數據庫構建環境 -->
<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="dbuser" />
<property name="password" value="123456" />
</dataSource>
</environment>
</environments>
<!-- 定義映射器 -->
<mappers>
<package name="com.gethin.mapper"/>
</mappers>
</configuration>
測試題Main
public class Main {
public static void main(String[] args) {
String resource="mybatis-config.xml";
InputStream inputStream=null;
try {
inputStream = Resources.getResourceAsStream(resource);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
SqlSessionFactory sqlSessionFactory=null;
sqlSessionFactory=new SqlSessionFactoryBuilder().build(inputStream);
SqlSession sqlSession=null;
try {
sqlSession=sqlSessionFactory.openSession();
RoleMapper roleMapper=sqlSession.getMapper(RoleMapper.class);
Role role=roleMapper.getRole(1L);
System.out.println(role.getId()+":"+role.getRoleName()+":"+role.getNote());
sqlSession.commit();
} catch (Exception e) {
// TODO Auto-generated catch block
sqlSession.rollback();
e.printStackTrace();
}finally {
sqlSession.close();
}
}
}
通過執行Main類,並設立斷點,就可以一步一步進行源碼的調試以及閱讀了。
4:遇到的問題
java.io.IOException: Could not find resource mybatis.xml
因爲這個配置文件是我在手動建立的包裏,需要將這個包定義爲資源文件。
java.lang.ClassNotFoundException: Cannot find class: com.mysql.cj.jdbc.Driver
出現這個文件,首先看自己的mysql的jar包是否導入。
如果不在,則在mybatis中加入這個依賴
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.44</version>
</dependency>
參考:https://www.jianshu.com/p/e739afb8fe31