mybatis详解-(5)面向接口

前面helloworld中通过selectOne完成了一次查询，但是那种方法需要将所有的参数都写在代码中，包括配置文件的命名空间。这里提供一种通过接口式编程，将所有的方法都定义为接口。在代码中调用接口，实际传递的参数都放置在配置文件中。

1.创建实例对象

Employee

package org.mybatis.settings;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.创建该业务的方法接口

EmployeeMapper

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

3.创建mybatis全局配置文件

mybatis-config.xml

<?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>    <environments default="development">        <environment id="development">            <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/settingsmapper.xml"/>    </mappers></configuration>

4.创建映射配置文件

settingsmapper.xml

<?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:名称空间，使用接口后，该项的值为接口的全类名    id:标记的唯一标识，使用接口后，跟接口中的方法名進行绑定    resultType:返回值类型，想要封装成什么对象    #{id}:从传递的参数取得的值    public Employee getEmpById(Integer id); --><mapper namespace="org.mybatis.settings.EmployeeMapper">    <!-- 这里并没有给last_name起别名lastName，这里是通过配置文件中驼峰命名规则进行注入 -->    <select id="getEmpById" resultType="org.mybatis.settings.Employee">        select id,last_name,email,gender from mybatis_employee where id = #{id}    </select></mapper>

5.创建测试类

package org.mybatis.settings;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.settings.Employee;/** * 使用接口式編程 */public class MybatisTest {    public SqlSessionFactory getSqlSessionFactory() throws IOException{        //全局配置文件        String resource = "mybatis-config.xml";        InputStream inputStream = Resources.getResourceAsStream(resource);        //获取SqlSessionFactory对象，读取配置文件        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);        return sqlSessionFactory;    }    @Test    public void testMybatis() {        try {            //1获取sqlSessionFactory对象            SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();            //2获取SqlSession对象，由于SqlSession是非线程安全的，所以不能写成成员变量，            //如果写成成员，有可能会出現资源竞争            //所以每次使用都应该获取新的对象            SqlSession openSession = sqlSessionFactory.openSession();            //3获取接口实现类的对象            //实际上创建的是一個代理对象，然後由代理对象完成增刪改查            EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);            System.out.println(mapper.getClass());            //4调用接口方法            Employee emp = mapper.getEmpById(2);            System.out.println(emp);            openSession.close();        } catch (IOException e) {            // TODO Auto-generated catch block            e.printStackTrace();        } finally {        }    }}

6.执行结果

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.
class com.sun.proxy.$Proxy2
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.