MyBatis(3)-映射文件
阿新 • • 發佈：2018-09-29
close 運行 ioe 進行 ssi 配置 接口類 ont HERE
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映射文件：
主要是在xxxmapper.xml文件裏的配置
映射文件指導這MyBatis如何進行數據庫的增刪該查，有著很重要的意義。
下面開始進入正題，最後會發一個完整版的代碼
因為實現的主要內容是增刪改查，所以我們現在接口類中定義好相關的方法，後面不在進行單一的定義！
工程的目錄如下：
EmployeeMapper.java
package com.MrChengs.dao; import java.util.Map; importorg.apache.ibatis.annotations.Param; import org.apache.ibatis.annotations.Select; import com.MrChengs.bean.Employee; public interface EmployeeMapper {
//我們直接傳入map public Employee getByMap(Map<String,Object> map); //查詢滿足兩個條件的數據 public Employee getByIdAndNames(@Param("id")int id,@Param("name")String name);//查詢 public Employee getEmployee(int id); //增加 public void addEmp(Employee employee); //更新 public void updateEmp(Employee employee); //刪除 public void deleteById(int id); }
1）insert-映射插入語句
1.1）EmployeeMapper.xml
<insert id="addEmp" > insert into test(name,gender,email) values(#{name},#{gender},#{email})1.2）在測試類中MyBatisTest.java</insert>
@Test public void test2() throws IOException{ //1.得到SqlSeesionFactory SqlSessionFactory sessionFactory = getSqlSessionFactory(); //2.得到SqlSession SqlSession sqlSession = sessionFactory.openSession(); try{ EmployeeMapper mapper = (EmployeeMapper) sqlSession.getMapper(EmployeeMapper.class); //手動添加數據： Employee em = new Employee( "zhangsan", "boy", "[email protected]"); mapper.addEmp(em); //手動提交數據 sqlSession.commit(); }finally{ sqlSession.close(); }}
1.3)測試成功
2）update映射更新語句
2.1）EmployeeMapper.xml
<update id="updateEmp"> update test set name=#{name},gender=#{gender} where id=#{id} </update>
2.2）測試類中
@Test public void test3() throws IOException{ //1.得到SqlSeesionFactory SqlSessionFactory sessionFactory = getSqlSessionFactory(); //2.得到SqlSession SqlSession sqlSession = sessionFactory.openSession(); try{ EmployeeMapper mapper = (EmployeeMapper) sqlSession.getMapper(EmployeeMapper.class); //手動添加數據： Employee em = new Employee( 6,"Jerry", "gril", null); mapper.updateEmp(em); //手動提交數據 sqlSession.commit(); }finally{ sqlSession.close();}}
2.3）測試成功！
3）delete-映射刪除操作
3.1）EmployeeMapper.xml
<delete id="deleteById"> delete from test where id=#{id} </delete>
3.2）測試類中
@Test public void test4() throws IOException{ //1.得到SqlSeesionFactory SqlSessionFactory sessionFactory = getSqlSessionFactory(); //2.得到SqlSession SqlSession sqlSession = sessionFactory.openSession(); try{ EmployeeMapper mapper = (EmployeeMapper) sqlSession.getMapper(EmployeeMapper.class); //手動添加數據： mapper.deleteById(6); //手動提交數據 sqlSession.commit(); }finally{ sqlSession.close();}}
3.3）測試成功！
4）關於主鍵的值問題
有時候需要用到主鍵值的問題，所以我們需要去學習這個知識點！
4.1）EmployeeMapper.xml
<!-- useGeneratedKeys="true"使用自增主鍵獲取主鍵的值 -->
<!-- keyProperty=""接受對應的主鍵值-->
<insert id="addEmp" useGeneratedKeys="true" keyProperty="id">
insert into test(name,gender,email) values(#{name},#{gender},#{email})
</insert>
4.2)測試類
@Test public void test2() throws IOException{ //1.得到SqlSeesionFactory SqlSessionFactory sessionFactory = getSqlSessionFactory(); //2.得到SqlSession SqlSession sqlSession = sessionFactory.openSession(); try{ EmployeeMapper mapper = (EmployeeMapper) sqlSession.getMapper(EmployeeMapper.class); //手動添加數據： Employee em = new Employee( "zhangsan", "boy", "[email protected]"); mapper.addEmp(em); //獲取主鍵值的屬性值進行打印 System.out.println(em.getId()); //手動提交數據 sqlSession.commit(); }finally{ sqlSession.close(); } }
4.3）測試成功
5）參數處理
5.1）單個參數：MyBatis不會做任何處理
#{參數名} ： 取出參數值
5.1.1）xml配置文件中
<select id="getId" resultType="com.MrChengs.bean.Employee"> select id,name,gender,email from test where id = #{idabc} </select>
5.1.2）測試類
@Test public void test() throws IOException { String resource = "mybatis-config.xml"; InputStream inputStream = Resources.getResourceAsStream(resource); SqlSessionFactory sqlSessionFactory = (SqlSessionFactory) new SqlSessionFactoryBuilder().build(inputStream); SqlSession session = sqlSessionFactory.openSession(); try{ Employee employee = session.selectOne("getId",5); System.out.println(employee); }finally{ session.close(); } }
5.1.3）測試是成功的！
5.2）多個參數時
MyBatis會做特殊的處理
多個參數時封裝成map
key param1 ,param2......
value 傳入的值
5.2.1）接口類中的查詢代碼設計如上所展示的
public Employee getByIdAndNames(@Param("id")int id,@Param("name")String name);
此時去掉@param：
public Employee getByIdAndNames(int id,String name);
5.2.2) xml文件
<select id="getByIdAndNames" resultType="com.MrChengs.bean.Employee" > select id,name,gender,email from test where id = #{id} and name=#{name} </select>
5.2.3）測試代碼
@Test public void test5() throws IOException{ SqlSessionFactory sessionFactory = getSqlSessionFactory(); SqlSession sqlSession = sessionFactory.openSession(); try{ EmployeeMapper mapper = sqlSession.getMapper(EmployeeMapper.class); Employee employee = mapper.getByIdAndNames(5, "MrChengs"); System.out.println(employee); }finally{ sqlSession.close(); } }
5.2.4）此時會報錯
5.2.5）處理方案：是在EmployeeMapper.xml文件中修改的
<!-- 同時使用兩個參數進行數據庫的查詢 -->
<!-- public Employee getByIdAndNames(int id,String name); -->
<select id="getByIdAndNames" resultType="com.MrChengs.bean.Employee" >
select id,name,gender,email from test where id = #{param1}
and name=#{param2}
</select>
此時得到正確的答案！
5.3）多個查詢字段時推薦使用的命名字段
明確指定封裝參數時的map和key @param("id") key:使用@param指定的值 5.3.1）接口類中public Employee getByIdAndNames(@Param("id")int id,@Param("name")String name);
5.3.2）xml文件中
<select id="getByIdAndNames" resultType="com.MrChengs.bean.Employee" > select id,name,gender,email from test where id = #{id} and name=#{name} </select>
測試類是5.2.3中的測試類，此時可以得到正確的結果！ 5.4） pojo： 如果參數過多，正好是業務邏輯的數據模型，我們直接傳入pojo剛剛好 #{屬性名} ： 取出傳入的pojo的屬性值 如果多個參數不是業務邏輯數據，沒有對應pojo，為了方法我們也可以直接傳入map #{key}就是取出對應的值 5.4.1）接口類中的
public Employee getByMap(Map<String,Object> map);
5.4.2）xml文件中添加
<select id="getByMap" resultType="com.MrChengs.bean.Employee" > select id,name,gender,email from test where id = #{id} and name=#{name} </select>
5.4.3）測試類
@Test public void test6() throws IOException{ SqlSessionFactory sessionFactory = getSqlSessionFactory(); SqlSession sqlSession = sessionFactory.openSession(); try{ EmployeeMapper mapper = sqlSession.getMapper(EmployeeMapper.class); Map<String, Object> map = new HashMap<>(); map.put("id", 5); map.put("name", "MrChengs"); Employee employee = mapper.getByMap(map); System.out.println(employee); }finally{ sqlSession.close(); } }
運行時，可以正確輸出結果!
5.5）思考問題註意
未完，待更新....
MyBatis(3)-映射文件