mybatis详解-(10)别名

前面已经介绍到了参数的传递，但是在真个过程中都使用的是全类名。本篇介绍使用别名：

1.创建实体类

package org.mybatis.typeAliases;import org.apache.ibatis.type.Alias;public class Employee {    private Integer id;    private String lastName;    private String email;    private String gender;    public Integer getId() {        return id;    }    public void setId(Integer id) {        this.id = id;    }    public String getLastName() {        return lastName;    }    public void setLastName(String lastName) {        this.lastName = lastName;    }    public String getEmail() {        return email;    }    public void setEmail(String email) {        this.email = email;    }    public String getGender() {        return gender;    }    public void setGender(String gender) {        this.gender = gender;    }    @Override    public String toString() {        return "Employee [id=" + id + ", lastName=" + lastName + ", email=" + email                + ", gender=" + gender + "]";    }}

2.创建mapper接口

package org.mybatis.typeAliases;public interface EmployeeMapper {    public Employee getEmpById(Integer id);}

3.创建主配置文件

<?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>    <!--         引入外部资源文件        resource:引入类路径下的资源文件        url:引入磁盘或者网络路径下的资源文件     -->    <properties resource="db.properties"></properties>    <!--         配置驼峰命名规则     -->    <settings>        <setting name="mapUnderscoreToCamelCase" value="true"/>    </settings>    <!--         typeAliases:别名处理器，为java类起别名     -->    <typeAliases>        <!-- type为全类名，alias为别名，这里是指定一个类 -->        <typeAlias type="org.mybatis.typeAliases.Employee" alias="emp"/>    </typeAliases>    <!-- 默认development是开发环境，如果改成test则表示使用测试环境 -->    <environments default="dev_mysql">        <environment id="dev_mysql">            <transactionManager type="JDBC" />            <dataSource type="POOLED">                <property name="driver" value="${mysql.driver}" />                <property name="url" value="${mysql.url}" />                <property name="username" value="${mysql.username}" />                <property name="password" value="${mysql.password}" />            </dataSource>        </environment>    </environments>     <mappers>        <mapper resource="mapper/typeAliasesmapper.xml"/>    </mappers></configuration>

4.创建mapper配置文件

<?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"><!--     namespace:名稱空間，使用接口后，該項的值為接口的全類名    id:標籤的唯一標識，使用接口后，跟接口中的方法名進行綁定    resultType:返回值類型，想要封裝成什麼對象    #{id}:從傳遞的參數取得的值    public Employee getEmpById(Integer id); --><mapper namespace="org.mybatis.typeAliases.EmployeeMapper">    <!-- resultType使用别名 -->    <select id="getEmpById" resultType="emp">        select id,last_name,email,gender from mybatis_employee where id = #{id}    </select></mapper>

5.创建测试类

package org.mybatis.typeAliases;import java.io.IOException;import java.io.InputStream;import org.apache.ibatis.io.Resources;import org.apache.ibatis.session.SqlSession;import org.apache.ibatis.session.SqlSessionFactory;import org.apache.ibatis.session.SqlSessionFactoryBuilder;import org.junit.Test;import org.mybatis.typeAliases.Employee;/** * 使用接口式編程 */public class MybatisTest {    @Test    public void testMybatis() {        String resource = "mybatis-config-typeAliases.xml";//全局配置文件        InputStream inputStream = null;        SqlSessionFactory sqlSessionFactory = null;        SqlSession sqlSession = null;        try {            inputStream = Resources.getResourceAsStream(resource);            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);            sqlSession = sqlSessionFactory.openSession();            EmployeeMapper mapper = sqlSession.getMapper(EmployeeMapper.class);            Employee emp = mapper.getEmpById(2);            System.out.println(emp);        } catch (IOException e) {            e.printStackTrace();        } finally {            sqlSession.close();        }    }}

6.测试结果

DEBUG - Logging initialized using ‘class org.apache.ibatis.logging.slf4j.Slf4jImpl’ adapter.
DEBUG - PooledDataSource forcefully closed/removed all connections.
DEBUG - PooledDataSource forcefully closed/removed all connections.
DEBUG - PooledDataSource forcefully closed/removed all connections.
DEBUG - PooledDataSource forcefully closed/removed all connections.
DEBUG - Openning JDBC Connection
DEBUG - Created connection 665188480.
DEBUG - ooo Using Connection [com.mysql.jdbc.JDBC4Connection@27a5f880]
DEBUG - ==> Preparing: select id,last_name,email,gender from mybatis_employee where id = ?
DEBUG - ==> Parameters: 2(Integer)
Employee [id=2, lastName=lisi, email=[e-mail], gender=2]
DEBUG - Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@27a5f880]
DEBUG - Closing JDBC Connection [com.mysql.jdbc.JDBC4Connection@27a5f880]
DEBUG - Returned connection 665188480 to pool.

7.使用注解方案

Employee实体添加注解empp

@Alias("empp")public class Employee {    private Integer id;    private String lastName;    private String email;    private String gender;

主配置文件使用包扫描

<typeAliases>    <!-- type为全类名，alias为别名，这里是指定一个类 -->    <!--  <typeAlias type="org.mybatis.typeAliases.Employee" alias="emp"/>-->       <!-- 为包下的所有类起别名，默认为类名大小写（不区分大小写） -->    <package name="org.mybatis.typeAliases"/></typeAliases>

映射配置文件使用别名empp

<!-- <select id="getEmpById" resultType="Employee"> --><!-- 如果上面没有添加注解empp，那么这里的resultType的值填写类名小写employee也可以进行数据封装，但是如果一个工程中出现多个类名相同的类就容易出现错误，所以不建议使用 --><select id="getEmpById" resultType="empp">select id,last_name,email,gender from mybatis_employee where id = #{id}</select>

运行结果：

DEBUG - Checking to see if class org.mybatis.typeAliases.MybatisTest matches criteria [is assignable to Object]
DEBUG - PooledDataSource forcefully closed/removed all connections.
DEBUG - PooledDataSource forcefully closed/removed all connections.
DEBUG - PooledDataSource forcefully closed/removed all connections.
DEBUG - PooledDataSource forcefully closed/removed all connections.
DEBUG - Openning JDBC Connection
DEBUG - Created connection 1399499405.
DEBUG - ooo Using Connection [com.mysql.jdbc.JDBC4Connection@536aaa8d]
DEBUG - ==> Preparing: select id,last_name,email,gender from mybatis_employee where id = ?
DEBUG - ==> Parameters: 2(Integer)
Employee [id=2, lastName=lisi, email=[e-mail], gender=2]
DEBUG - Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@536aaa8d]
DEBUG - Closing JDBC Connection [com.mysql.jdbc.JDBC4Connection@536aaa8d]
DEBUG - Returned connection 1399499405 to pool.