别名的设置:(别名不区分大小写):
设置单个别名:
<configuration> <properties resource="db.properties" /> <typeAliases> <!-- 设置单个别名 --> <typeAlias type="com.offcn.entity.Person" alias="person"/> <typeAlias type="com.offcn.entity.Book" alias="book"/> </typeAliases>
映射文件中直接写别名即可:
<select id="queryPersonById" parameterType="int" resultType="person"> select * from person where id = #{id} </select>
批量设置别名:
<typeAliases> <!-- 批量定义别名 ,别名不区分大小写,会将该包下的所有文件批量设置别名--> <package name="com.offcn.entity"/> </typeAliases>
类型转换器:
1.MyBatis自带的类型转换器:
2.自定义的类型转换器:
步骤:
a.创建转换器:需要实现TypeHandler接口,实现转换器有两种方式:
i.实现接口TypeHandler
ii.继承BaseTypeHander
创建converter转换器,代码如下:
package com.offcn.converter; import java.sql.CallableStatement; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import org.apache.ibatis.type.BaseTypeHandler; import org.apache.ibatis.type.JdbcType; public class BooleanToIntConverter extends BaseTypeHandler<Boolean>{ //DB ---> java @Override //根据名字拿 public Boolean getNullableResult(ResultSet rs, String columnName) throws SQLException { // TODO Auto-generated method stub int sexNo = rs.getInt(columnName); return sexNo == 1?true:false; } //根据下标拿 @Override public Boolean getNullableResult(ResultSet rs, int columnIndex) throws SQLException { // TODO Auto-generated method stub int sexNo = rs.getInt(columnIndex); return sexNo == 1?true:false; } //根据存储过程拿 @Override public Boolean getNullableResult(CallableStatement cs, int columnIndex) throws SQLException { // TODO Auto-generated method stub int sexNo = cs.getInt(columnIndex); return sexNo == 1?true:false; } //java ---> DB @Override public void setNonNullParameter(PreparedStatement ps, int i, Boolean parameter, JdbcType jdbc) throws SQLException { // TODO Auto-generated method stub if(parameter) { ps.setInt(i, 1); }else { ps.setInt(i, 0); } } }
在conf.xml文件中配置类型转换器:
<typeHandlers> <typeHandler handler="com.offcn.converter.BooleanToIntConverter" javaType="Boolean" jdbcType="INTEGER"/> </typeHandlers>
映射文件中查找的sql:(DB ---> JAVA)
<!-- 带类型转换器的查询 --> <select id="queryPersonByIdWithConverter" parameterType="int" resultMap="personResult"> select * from person where id = #{id} </select> <resultMap type="person" id="personResult"> <!-- 分为主键和非主键,主键用id,非主键用result --> <id property="id" column="id"/> <result property="name" column="name"/> <result property="bir" column="bir"/> <result property="address" column="address"/> <result property="sex" column="sex" javaType="Boolean" jdbcType="INTEGER" /> </resultMap>
接口中定义对应的方法:
Person queryPersonByIdWithConverter(int id);
测试类进行测试:
public static void queryPersonByIdWithConverter() throws IOException { //读取conf.xml文件 Reader reader = Resources.getResourceAsReader("conf.xml"); //创建sqlSessionFactory SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(reader); //获取sqlSession SqlSession session = sessionFactory.openSession(); //通过session定位映射文件 personMapper personMapper = session.getMapper(personMapper.class); //定位sql语句并执行 Person person = personMapper.queryPersonByIdWithConverter(4); //提交事务 session.commit(); System.out.println(person); //关闭连接 session.close(); }
映射文件中增加的sql:(JAVA --> DB)
<!-- 带类型转转器的增加 --> <insert id="insertPersonWithConverter" parameterType="person" > insert into person (name,bir,address,sex) value (#{name},#{bir},#{address},#{sex,javaType=Boolean,jdbcType=INTEGER}) </insert>
接口中定义对应的方法:
测试类进行测试:
//带转换器的增加操作 public static void insertPersonWithConverter() throws IOException { //读取conf.xml文件 Reader reader = Resources.getResourceAsReader("conf.xml"); //获取sqlSessionFactory SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(reader); //获取sqlSession SqlSession session = sessionFactory.openSession(); //定位映射文件的位置 personMapper personMapper = session.getMapper(personMapper.class); //定位sql并执行 Person person = new Person("小孙",new Date(),"青岛",true); personMapper.insertPersonWithConverter(person); //提交事务 session.commit(); System.out.println("增加成功"); //关闭连接 session.close(); }
最后关于:sql标签中什么时候用resultType什么时候用resultMap
1.如果表中字段和实体类中的属性的类型合理识别,则用resultType,否则用resultMap
2.如果表中字段的名字和实体类中属性名能够合理识别,则用resultType,否则用resultMap
原文地址:https://www.cnblogs.com/man-tou/p/11335402.html
时间: 2024-11-03 21:03:09