mybatis 运行时加载自定义mapper文件
mybatis 运行时加载自定义mapper文件
用mybatis一定要写mapper文件,这是使用mybatis的常识,但有时候应用需求,mapper文件中的节点需要动态生成,或者根据业务场景进行组装,那这个时候的SQL语句直接写在mapper文件显然不可取,又或者采用动态SQL完成,今天介绍一种方式,支行时加载自定义mapper配置文件。
我首先介绍一种mapper文件存在的写法,也是大家常用的,至于spring-mybatis配置方法,我这里就不列了:
dao接口:
package com.springmvc.mybatis.dao;
import java.util.List;
public interface DatabaseObjectQueryDao {
List<String> getAllSequence();
}
mapper文件:
<?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.springmvc.mybatis.dao.DatabaseObjectQueryDao">
<select id="getAllSequence" resultType="String">
select sysdate from dual
</select>
</mapper>
好,大家注意了, 下面开始分享无mapper动态加载写法!
dao接口:
package com.springmvc.mybatis.dao;
/**
* Discript:
*
* @author <a href="[email protected]">杨波</a>
* @date 创建时间:2018/10/11 15:33
*/
public interface LoadMapperFileDao {
String getAllSequence();
}
这里没有mapper文件,怎么办? 没有我们就给他造:
package com.springmvc.mybatis.test;
import org.apache.ibatis.builder.xml.XMLMapperBuilder;
import org.apache.ibatis.session.Configuration;
import org.apache.ibatis.session.SqlSessionFactory;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import java.io.ByteArrayInputStream;
import java.io.InputStream;
/**
* Discript:
*
* @author <a href="[email protected]">杨波</a>
* @date 创建时间:2018/10/11 15:01
*/
@Service
public class LoadMapperFileTest implements InitializingBean{
@Autowired
private SqlSessionFactory sqlSessionFactory;
private Configuration mapperConfig;
public void afterPropertiesSet() throws Exception {
//mapper文件的实际内容,此处可根据业务需求进行拼装文件内容
String contextXml = "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n" +
"<!DOCTYPE mapper PUBLIC \"-//mybatis.org//DTD Mapper 3.0//EN\" \n" +
"\"http://mybatis.org/dtd/mybatis-3-mapper.dtd\">\n" +
"<mapper namespace=\"com.springmvc.mybatis.dao.LoadMapperFileDao\">\n" +
"\t<select id=\"getAllSequence\" resultType=\"String\">\n" +
"\t\tselect sysdate from dual \n" +
"\t</select>\n" +
"</mapper>";
//一般与namespace相同
String mapperId = "com.springmvc.mybatis.dao.LoadMapperFileDao";
mapperConfig = sqlSessionFactory.getConfiguration();
try {
InputStream is = new ByteArrayInputStream(contextXml.getBytes());
XMLMapperBuilder xmlMapperBuilder = new XMLMapperBuilder(is, this.mapperConfig, mapperId, this.mapperConfig.getSqlFragments());
xmlMapperBuilder.parse();
System.out.println("自定义加载完毕!");
}catch (Exception e){
}
}
}
总体测试效果及结果代码如下, 大家可以看到DatabaseObjectQueryDao 调用的方法返回值是list所以结果有中括号。而LoadMapperFileDao调用方法返回的是string所以只看见一串时间 :