这一章我们练习一下Mybatis的别名，这大大的提高了我们的开发效率
类型别名（typeAliases）
类型别名是为 Java 类型设置一个短的名字。 它只和 XML 配置有关，作用在于用来减少类完全限定名的冗余。
目录：
我们只需要配置Mybatis-config文件和UserMapper.xml文件即可：
Mybatis-config.xml配置：
添加typeAliases标签，typeAlias可以自定义包的名字
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>
<properties resource="db.properties"/>
<typeAliases>
<typeAlias type="com.hdlf.pojo.User" alias="User">typeAlias>
typeAliases>
<environments default="development">
<environment id="development">
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<property name="driver" value="${driver}"/>
<property name="url" value="${url}"/>
<property name="username" value="${username}"/>
<property name="password" value="${password}"/>
dataSource>
environment>
environments>
<mappers>
<mapper resource="com/hdlf/dao/UserMapper.xml"/>
mappers>
configuration>
UserMapper.xml配置文件：
我们把原先的resultType的com.hdlf.pojo.User改成User之后看着是不是很舒服，也更加方便
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.hdlf.dao.UserMapper">
<select id="getUser" resultType="User">
SELECT * FROM mybatis.user
select>
<insert id="getinsert" parameterType="User" >
INSERT INTO mybatis.user(id,name,pwd) values (#{id},#{name},#{pwe})
insert>
<delete id="getdelete" parameterType="int">
DELETE FROM mybatis.user WHERE id = #{id}
delete>
<update id="getupdate" parameterType="User">
update mybatis.user set name=#{name},pwd=#{pwe} where id=#{id};
update>
<select id="getselect" resultType="User" parameterType="int">
SELECT * FROM mybatis.user WHERE id = #{id}
select>
mapper>
结果：
可以正常运行
接下来我们使用package属性来测试一下
把typeAlias改成package
Mybatis-config.xml配置：
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>
<properties resource="db.properties"/>
<typeAliases>
<package name="com.hdlf.pojo"/>
typeAliases>
<environments default="development">
<environment id="development">
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<property name="driver" value="${driver}"/>
<property name="url" value="${url}"/>
<property name="username" value="${username}"/>
<property name="password" value="${password}"/>
dataSource>
environment>
environments>
<mappers>
<mapper resource="com/hdlf/dao/UserMapper.xml"/>
mappers>
configuration>
UserMapper.xml配置：
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.hdlf.dao.UserMapper">
<select id="getUser" resultType="user">
SELECT * FROM mybatis.user
select>
<insert id="getinsert" parameterType="user" >
INSERT INTO mybatis.user(id,name,pwd) values (#{id},#{name},#{pwe})
insert>
<delete id="getdelete" parameterType="int">
DELETE FROM mybatis.user WHERE id = #{id}
delete>
<update id="getupdate" parameterType="user">
update mybatis.user set name=#{name},pwd=#{pwe} where id=#{id};
update>
<select id="getselect" resultType="user" parameterType="int">
SELECT * FROM mybatis.user WHERE id = #{id}
select>
mapper>
结果无疑是和上面的结果是一样的。
还要一种是注解别名这个更方便，@Alias("name")只需要在实体类上就可以
User类：
package com.hdlf.pojo; import org.apache.ibatis.type.Alias; //mybatis注解别名 @Alias("user") public class User { private int id; private String name; private String pwd; @Override public String toString() { return "User{" + "id=" + id + ", name='" + name + '\'' + ", pwe='" + pwd + '\'' + '}'; } public User() { } public User(int id, String name, String pwe) { this.id = id; this.name = name; this.pwd = pwe; } public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getPwe() { return pwd; } public void setPwe(String pwe) { this.pwd = pwe; } }