mybatis详解-(13)注解操作查询

前面讲述的内容中，基本都是按照同样的步骤1）创建接口类，2）创建主配置文件，3）创建接口映射文件。在接口类中定义实现的接口功能，在映射配置文件中写具体的完成接口类容的sql语句，然后在主配置文件中应用映射配置文件操作相关的操作。mybatis也提供了一套通过接口操作数据请求的注解，比如要完成一个查询操作，可以按照如下的步骤完成：

1.创建实体类

Employee

package org.mybatis.annotation;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.创建方法接口类

EmployeeAnnotation
在接口方法上面添加@Select注解，在注解中添加实际的操作sql语句。还有其他的相关注解如@Insert等，更详细的内容可参考MybatisApi

package org.mybatis.annotation;import org.apache.ibatis.annotations.Select;public interface EmployeeAnnotation {    @Select("select * from mybatis_employee where id = #{id}")    public Employee getEmployeeById(int id);}

3.创建主配置文件

mybatis-config-annotation.xml
在主配置文件中引用接口类org.mybatis.annotation.EmployeeAnnotation

<?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"></properties>    <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>        <!-- 通过注解的形式，不需要mapper配置文件 。但是这样存在硬编码，所以需要优化的，经常变的不要写在这里-->        <mapper class="org.mybatis.annotation.EmployeeAnnotation"/>        <!-- 也可以直接通过包，不指定具体类 -->        <!-- <package name="org.mybatis.annotation"/> -->    </mappers></configuration>

4.创建测试类

package org.mybatis.annotation;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;/** * 使用接口式編程 */public class MybatisTest {    @Test    public void testMybatis() {        String resource = "mybatis-config-annotation.xml";        InputStream inputStream = null;        SqlSessionFactory sqlSessionFactory = null;        SqlSession sqlSession = null;        try {            inputStream = Resources.getResourceAsStream(resource);            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);            sqlSession = sqlSessionFactory.openSession();            EmployeeAnnotation mapper = sqlSession.getMapper(EmployeeAnnotation.class);            Employee employee = mapper.getEmployeeById(2);            System.out.println(employee);        } catch (IOException e) {            e.printStackTrace();        } finally {            sqlSession.close();        }    }}

5.测试结果

DEBUG - Openning JDBC Connection
DEBUG - Created connection 527446182.
DEBUG - ooo Using Connection [com.mysql.jdbc.JDBC4Connection@1f7030a6]
DEBUG - ==> Preparing: select * 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@1f7030a6]
DEBUG - Closing JDBC Connection [com.mysql.jdbc.JDBC4Connection@1f7030a6]
DEBUG - Returned connection 527446182 to pool.

这个步骤中省略了创建映射配置文件的步骤，直接在主配置文件中引用接口类。
但是这种方式也存在一定的问题，比如这样操作是硬编码，为以后的修改和调试都埋下隐患。建议还是使用映射配置文件的方式来操作。