04.MyBatis别名的设置和类型转换器

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 stubint sexNo = rs.getInt(columnName);return sexNo == 1?true:false;}//根据下标拿
    @Overridepublic Boolean getNullableResult(ResultSet rs, int columnIndex) throws SQLException {// TODO Auto-generated method stubint sexNo = rs.getInt(columnIndex);return sexNo == 1?true:false;}//根据存储过程拿
    @Overridepublic Boolean getNullableResult(CallableStatement cs, int columnIndex) throws SQLException {// TODO Auto-generated method stubint sexNo = cs.getInt(columnIndex);return sexNo == 1?true:false;}//java ---> DB
    @Overridepublic void setNonNullParameter(PreparedStatement ps, int i, Boolean parameter, JdbcType jdbc) throws SQLException {// TODO Auto-generated method stubif(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sqlSessionFactorySqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(reader);//获取sqlSessionSqlSession 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sqlSessionFactorySqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(reader);//获取sqlSessionSqlSession 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();}