• Mybatis ResultType处理返回类型

    目录

     1. 使用resultType返回List

     2. 使用resultType返回单个对象

    3. 使用resultType返回List，适用于多表查询返回结果集 

     4. 使用resultType返回Map，适用于多表查询返回单个结果集,object>

     1. 使用resultType返回List

    • Mapper.xml 
    1. <select id="resultType2" resultType="String">
    2.     select
    3.     book_name
    4.     from tb_book
    5.   select>
    •  service层
    List resultType2();
    • 实现类
    1.     //创建对象
    2.     private BookMapper bookMapper;
    3.  
    4.  
    5.     /**
    6.      * 给bookMapper set,get方法
    7.      * @return
    8.      */
    9.     public BookMapper getBookMapper() {
    10.         return bookMapper;
    11.     }
    12.  
    13.     public void setBookMapper(BookMapper bookMapper) {
    14.         this.bookMapper = bookMapper;
    15.     }
    16.  
    17.     @Override
    18.     public List resultType2() {
    19.         return bookMapper.resultType2();
    20.     }
    •  使用junit测试
    1. package com.jmh.mybatis.service.impl;
    2.  
    3. import com.jmh.mybatis.mapper.BookMapper;
    4. import com.jmh.mybatis.model.Book;
    5. import com.jmh.mybatis.model.BookVo;
    6. import com.jmh.mybatis.service.IBookService;
    7. import com.jmh.mybatis.utils.MybatisSqlSessionFactory;
    8. import org.apache.ibatis.annotations.MapKey;
    9. import org.apache.ibatis.session.SqlSession;
    10. import org.junit.After;
    11. import org.junit.Before;
    12. import org.junit.Test;
    13.  
    14. import java.util.List;
    15. import java.util.Map;
    16. import java.util.Set;
    17.  
    18. import static org.junit.Assert.*;
    19.  
    20. public class DemoTest {
    21.     //获取对象
    22.     private Book book;
    23.     private IBookService iBookService;
    24.     private SqlSession sqlSession;
    25.  
    26.     @Before
    27.     public void setUp() throws Exception {
    28.         book=new Book();
    29.         sqlSession = MybatisSqlSessionFactory.getSqlsession();
    30.         BookMapper mapper = sqlSession.getMapper(BookMapper.class);
    31.         BookServiceImpl iml=new BookServiceImpl();
    32.         iml.setBookMapper(mapper);
    33.         iBookService= iml;
    34.     }
    35.  
    36.     @After
    37.     public void tearDown() throws Exception {
    38.         sqlSession.commit();
    39.         MybatisSqlSessionFactory.closeSqlsession();
    40.     }
    41.  
    42.  
    43.     @Test
    44.     public void resultType2() {
    45.         List books = iBookService.resultType2();
    46.         for (String b : books) {
    47.             System.out.println(b);
    48.         }
    49.     }
    50.  
    51. }
    •  测试如下

     

     2. 使用resultType返回单个对象

    • Mapper.xml 
    1.   <select id="resultType3" resultType="com.jmh.mybatis.model.Book">
    2.     select
    3.     <include refid="Base_Column_List" />
    4.     from tb_book where book_id=306
    5.   select>
    •  service层
    Book resultType3();
    •  实现类
    1.     //创建对象
    2.     private BookMapper bookMapper;
    3.  
    4.  
    5.     /**
    6.      * 给bookMapper set,get方法
    7.      * @return
    8.      */
    9.     public BookMapper getBookMapper() {
    10.         return bookMapper;
    11.     }
    12.  
    13.     public void setBookMapper(BookMapper bookMapper) {
    14.         this.bookMapper = bookMapper;
    15.     }
    16.  
    17.     @Override
    18.     public Book resultType3() {
    19.         return bookMapper.resultType3();
    20.     }
    •  使用junit测试
    1.     package com.jmh.mybatis.service.impl;
    2.  
    3. import com.jmh.mybatis.mapper.BookMapper;
    4. import com.jmh.mybatis.model.Book;
    5. import com.jmh.mybatis.model.BookVo;
    6. import com.jmh.mybatis.service.IBookService;
    7. import com.jmh.mybatis.utils.MybatisSqlSessionFactory;
    8. import org.apache.ibatis.annotations.MapKey;
    9. import org.apache.ibatis.session.SqlSession;
    10. import org.junit.After;
    11. import org.junit.Before;
    12. import org.junit.Test;
    13.  
    14. import java.util.List;
    15. import java.util.Map;
    16. import java.util.Set;
    17.  
    18. import static org.junit.Assert.*;
    19.  
    20. public class DemoTest {
    21.     //获取对象
    22.     private Book book;
    23.     private IBookService iBookService;
    24.     private SqlSession sqlSession;
    25.  
    26.     @Before
    27.     public void setUp() throws Exception {
    28.         book=new Book();
    29.         sqlSession = MybatisSqlSessionFactory.getSqlsession();
    30.         BookMapper mapper = sqlSession.getMapper(BookMapper.class);
    31.         BookServiceImpl iml=new BookServiceImpl();
    32.         iml.setBookMapper(mapper);
    33.         iBookService= iml;
    34.     }
    35.  
    36.     @After
    37.     public void tearDown() throws Exception {
    38.         sqlSession.commit();
    39.         MybatisSqlSessionFactory.closeSqlsession();
    40.     }
    41.  
    42.  
    43.     @Test
    44.     public void resultType3() {
    45.         Book book = iBookService.resultType3();
    46.         System.out.println(book);
    47.     }
    48.  
    49.  
    50.  
    51. }

    3. 使用resultType返回List，适用于多表查询返回结果集 

    • mapper接口 

        需要使用注解才能使用map其实这个主要功能也不大 将就着用吧

    1.     @MapKey("id")
    2.        List> resultType4();
    • mapper.xml 
    1.   <select id="resultType4" resultType="java.util.Map">
    2.     select book_id,price,book_name from tb_book
    3.   select>
    •  service层
    List> resultType4();
    •  实现类
    1.     //创建对象
    2.     private BookMapper bookMapper;
    3.  
    4.  
    5.     /**
    6.      * 给bookMapper set,get方法
    7.      * @return
    8.      */
    9.     public BookMapper getBookMapper() {
    10.         return bookMapper;
    11.     }
    12.  
    13.     public void setBookMapper(BookMapper bookMapper) {
    14.         this.bookMapper = bookMapper;
    15.     }
    16.     @Override
    17.     public List> resultType4() {
    18.         return bookMapper.resultType4();
    19.     }
    •  使用junit测试
    1. package com.jmh.mybatis.service.impl;
    2.  
    3. import com.jmh.mybatis.mapper.BookMapper;
    4. import com.jmh.mybatis.model.Book;
    5. import com.jmh.mybatis.model.BookVo;
    6. import com.jmh.mybatis.service.IBookService;
    7. import com.jmh.mybatis.utils.MybatisSqlSessionFactory;
    8. import org.apache.ibatis.annotations.MapKey;
    9. import org.apache.ibatis.session.SqlSession;
    10. import org.junit.After;
    11. import org.junit.Before;
    12. import org.junit.Test;
    13.  
    14. import java.util.List;
    15. import java.util.Map;
    16. import java.util.Set;
    17.  
    18. import static org.junit.Assert.*;
    19.  
    20. public class DemoTest {
    21.     //获取对象
    22.     private Book book;
    23.     private IBookService iBookService;
    24.     private SqlSession sqlSession;
    25.  
    26.     @Before
    27.     public void setUp() throws Exception {
    28.         book=new Book();
    29.         sqlSession = MybatisSqlSessionFactory.getSqlsession();
    30.         BookMapper mapper = sqlSession.getMapper(BookMapper.class);
    31.         BookServiceImpl iml=new BookServiceImpl();
    32.         iml.setBookMapper(mapper);
    33.         iBookService= iml;
    34.     }
    35.  
    36.     @After
    37.     public void tearDown() throws Exception {
    38.         sqlSession.commit();
    39.         MybatisSqlSessionFactory.closeSqlsession();
    40.     }
    41.  
    42.  
    43.     @Test
    44.     public void resultType4() {
    45.         List> maps = iBookService.resultType4();
    46.         for (Map map : maps) {
    47.             System.out.println(map);
    48.         }
    49.     }
    50.  
    51. }

     4. 使用resultType返回Map，适用于多表查询返回单个结果集

    •  mapper接口
    1. @MapKey("id")
    2.         Map resultType5();
    • mapper.xml 
    1.
    •  service层
    Map resultType5();
    •  实现类
    1.     //创建对象
    2.     private BookMapper bookMapper;
    3.  
    4.  
    5.     /**
    6.      * 给bookMapper set,get方法
    7.      * @return
    8.      */
    9.     public BookMapper getBookMapper() {
    10.         return bookMapper;
    11.     }
    12.  
    13.     public void setBookMapper(BookMapper bookMapper) {
    14.         this.bookMapper = bookMapper;
    15.     }
    16.  
    17.     @Override
    18.     public Map resultType5() {
    19.         return bookMapper.resultType5();
    20.     }
    •  使用junit测试
    1. package com.jmh.mybatis.service.impl;
    2.  
    3. import com.jmh.mybatis.mapper.BookMapper;
    4. import com.jmh.mybatis.model.Book;
    5. import com.jmh.mybatis.model.BookVo;
    6. import com.jmh.mybatis.service.IBookService;
    7. import com.jmh.mybatis.utils.MybatisSqlSessionFactory;
    8. import org.apache.ibatis.annotations.MapKey;
    9. import org.apache.ibatis.session.SqlSession;
    10. import org.junit.After;
    11. import org.junit.Before;
    12. import org.junit.Test;
    13.  
    14. import java.util.List;
    15. import java.util.Map;
    16. import java.util.Set;
    17.  
    18. import static org.junit.Assert.*;
    19.  
    20. public class DemoTest {
    21.     //获取对象
    22.     private Book book;
    23.     private IBookService iBookService;
    24.     private SqlSession sqlSession;
    25.  
    26.     @Before
    27.     public void setUp() throws Exception {
    28.         book=new Book();
    29.         sqlSession = MybatisSqlSessionFactory.getSqlsession();
    30.         BookMapper mapper = sqlSession.getMapper(BookMapper.class);
    31.         BookServiceImpl iml=new BookServiceImpl();
    32.         iml.setBookMapper(mapper);
    33.         iBookService= iml;
    34.     }
    35.  
    36.     @After
    37.     public void tearDown() throws Exception {
    38.         sqlSession.commit();
    39.         MybatisSqlSessionFactory.closeSqlsession();
    40. }
    41.  
    42.     @Test
    43.     public void resultType5() {
    44.         Map map = iBookService.resultType5();
    45.         System.out.println(map);
    46.     }
    47. }

     

     

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  • 原文地址：https://blog.csdn.net/m0_63300795/article/details/126204931