如何使用sqlsesson的getmapper獲取接口的實例

原文地址：https://zhidao.baidu.com/question/922756385577154179.html?fr=iks&word=session.getMapper&ie=gbk
1，本文采用的Mybatis框架版本爲： mybatis-3.0.4.jar
2， 以持久化一個簡單的User bean爲例
User實體類的代碼如下：
Java代碼  收藏代碼
    package bean;  
       public class User {  
           private String name;  
           private Integer age;  
           public String getName() {  
              return name;  
           }  
           public void setName(String name) {  
              this.name = name;  
           }  
           public Integer getAge() {  
              return age;  
           }  
           public void setAge(Integer age) {  
              this.age = age;  
           }  
           public User(String name, Integer age) {  
              super();  
              this.name = name;  
              this.age = age;  
           }  
           public User() {  
              super();  
           }  //必須要有這個無參構造方法，不然根據UserMapper.xml中的配置，在查詢數據庫時，將不能反射構造出User實例  
       }   
User實體的映射器取名爲UserMapper(接口)，其代碼如下
Java代碼  收藏代碼
    package Mapper;  
     import bean.User;  
     public interface UserMapper {  
         public void insertUser(User user);  
         public User getUser(String name);  
     }   
注意，該接口類似於Hibernate中的DAO層接口，唯一不同的是，MyBatis中，只聲明該接口就可以，不需要去實現.
UserMapper映射器對應的配置文件如下(相當於Hibernate中的User.hbm.xml,當然這裏面不是屬性映射字段，而是直接是映射器中各種方法對應的sql語句)：
    <?xml version="1.0" encoding="UTF-8" ?>  
       <!DOCTYPE mapper  
           PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"  
           >  
       <mapper namespace="Mapper.UserMapper">  
       <!-- 這裏namespace必須是UserMapper接口的路徑，不然要運行的時候要報錯 “is not known to the MapperRegistry”-->  
           <insert id="insertUser" parameterType="User">  
              insert into vincent_user(name,age) values(#{name},#{age})  
              <!-- 這裏sql結尾不能加分號，否則報“ORA-00911”的錯誤 -->  
           </insert>  
           <!-- 這裏的id必須和UserMapper接口中的接口方法名相同，不然運行的時候也要報錯 -->  
           <select id="getUser" resultType="User" parameterType="java.lang.String">  
               select * from vincent_user where name=#{name}  
           </select>  
       </mapper>  
MyBatis的配置文件這裏取名爲mybatis-config.xml其配置代碼如下(相當與Hibernate的hibernate.cfg.xml):
Xml代碼  收藏代碼
    <?xml version="1.0" encoding="UTF-8"?>  
        <!DOCTYPE configuration  
            PUBLIC "-// 3.0//EN"  
            "">  
        <configuration>  
            <settings>  
                <!-- changes from the defaults for testing -->  
                <setting name="cacheEnabled" value="false" />  
                <setting name="useGeneratedKeys" value="true" />  
                <setting name="defaultExecutorType" value="REUSE" />  
            </settings>  
            <typeAliases>  
               <typeAlias alias="User" type="bean.User"/>  
            </typeAliases>  
            <environments default="development">  
               <environment id="development">  
                   <transactionManager type="jdbc"/>  
                   <dataSource type="POOLED">  
                      <property name="driver" value="oracle.jdbc.driver.OracleDriver"/>  
                      <property name="url" value="jdbc:oracle:thin:@192.168.56.201:1521:system"/>  
                      <property name="username" value="vincent"/>  
                      <property name="password" value="1234"/>  
                   </dataSource>  
               </environment>  
            </environments>  
            <mappers>  
                <mapper resource="resource/UserMapper.xml" />  
            </mappers>  
        </configuration>   
加載配置文件得到sqlSessionFactory的工具類
Java代碼  收藏代碼
    package Util;  
        import java.io.IOException;  
        import java.io.Reader;  
        import org.apache.ibatis.io.Resources;  
        import org.apache.ibatis.session.SqlSessionFactory;  
        import org.apache.ibatis.session.SqlSessionFactoryBuilder;  
        public class MyBatisUtil  {  
            private  final static SqlSessionFactory sqlSessionFactory;  
            static {  
               String resource = "resource/mybatis-config.xml";  
               Reader reader = null;  
               try {  
                   reader = Resources.getResourceAsReader(resource);  
               } catch (IOException e) {  
                   System.out.println(e.getMessage());  
               }  
               sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);  
            }  
            public static SqlSessionFactory getSqlSessionFactory() {  
               return sqlSessionFactory;  
            }  
        }  
測試代碼如下：
Java代碼  收藏代碼
    package TestMapper;  
       import org.apache.ibatis.session.SqlSession;  
       import org.apache.ibatis.session.SqlSessionFactory;  
       import org.junit.Test;  
       public class TestMapper {  
           static SqlSessionFactory sqlSessionFactory = null;  
           static {  
              sqlSessionFactory = MyBatisUtil.getSqlSessionFactory();  
           }  
           @Test  
           public void testAdd() {  
              SqlSession sqlSession = sqlSessionFactory.openSession();  
              try {  
                  UserMapper userMapper = sqlSession.getMapper(UserMapper.class);  
                  User user = new User("tom",new Integer(5));  
                  userMapper.insertUser(user);  
                  sqlSession.commit();//這裏一定要提交，不然數據進不去數據庫中  
              } finally {  
                  sqlSession.close();  
              }  
           }  
           @Test  
           public void getUser() {  
              SqlSession sqlSession = sqlSessionFactory.openSession();  
              try {  
                  UserMapper userMapper = sqlSession.getMapper(UserMapper.class);  
                  User user = userMapper.getUser("jun");  
                  System.out.println("name: "+user.getName()+"|age: "+user.getAge());  
              } finally {  
                  sqlSession.close();  
              }  
           }  
       }