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<T>

• Mapper.xml 

<select id="resultType2" resultType="String">
    select
    book_name
    from tb_book
  </select>

•  service层

List<String> resultType2();

• 实现类

    //创建对象
    private BookMapper bookMapper;


    /**
     * 给bookMapper set,get方法
     * @return
     */
    public BookMapper getBookMapper() {
        return bookMapper;
    }

    public void setBookMapper(BookMapper bookMapper) {
        this.bookMapper = bookMapper;
    }

    @Override
    public List<String> resultType2() {
        return bookMapper.resultType2();
    }

•  使用junit测试

package com.jmh.mybatis.service.impl;

import com.jmh.mybatis.mapper.BookMapper;
import com.jmh.mybatis.model.Book;
import com.jmh.mybatis.model.BookVo;
import com.jmh.mybatis.service.IBookService;
import com.jmh.mybatis.utils.MybatisSqlSessionFactory;
import org.apache.ibatis.annotations.MapKey;
import org.apache.ibatis.session.SqlSession;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import java.util.List;
import java.util.Map;
import java.util.Set;

import static org.junit.Assert.*;

public class DemoTest {
    //获取对象
    private Book book;
    private IBookService iBookService;
    private SqlSession sqlSession;

    @Before
    public void setUp() throws Exception {
        book=new Book();
        sqlSession = MybatisSqlSessionFactory.getSqlsession();
        BookMapper mapper = sqlSession.getMapper(BookMapper.class);
        BookServiceImpl iml=new BookServiceImpl();
        iml.setBookMapper(mapper);
        iBookService= iml;
    }

    @After
    public void tearDown() throws Exception {
        sqlSessionmit();
        MybatisSqlSessionFactory.closeSqlsession();
    }


    @Test
    public void resultType2() {
        List<String> books = iBookService.resultType2();
        for (String b : books) {
            System.out.println(b);
        }
    }

}

•  测试如下

 2. 使用resultType返回单个对象

• Mapper.xml 

  <select id="resultType3" resultType="com.jmh.mybatis.model.Book">
    select
    <include refid="Base_Column_List" />
    from tb_book where book_id=306
  </select>

•  service层

Book resultType3();

•  实现类

    //创建对象
    private BookMapper bookMapper;


    /**
     * 给bookMapper set,get方法
     * @return
     */
    public BookMapper getBookMapper() {
        return bookMapper;
    }

    public void setBookMapper(BookMapper bookMapper) {
        this.bookMapper = bookMapper;
    }

    @Override
    public Book resultType3() {
        return bookMapper.resultType3();
    }

•  使用junit测试

    package com.jmh.mybatis.service.impl;

import com.jmh.mybatis.mapper.BookMapper;
import com.jmh.mybatis.model.Book;
import com.jmh.mybatis.model.BookVo;
import com.jmh.mybatis.service.IBookService;
import com.jmh.mybatis.utils.MybatisSqlSessionFactory;
import org.apache.ibatis.annotations.MapKey;
import org.apache.ibatis.session.SqlSession;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import java.util.List;
import java.util.Map;
import java.util.Set;

import static org.junit.Assert.*;

public class DemoTest {
    //获取对象
    private Book book;
    private IBookService iBookService;
    private SqlSession sqlSession;

    @Before
    public void setUp() throws Exception {
        book=new Book();
        sqlSession = MybatisSqlSessionFactory.getSqlsession();
        BookMapper mapper = sqlSession.getMapper(BookMapper.class);
        BookServiceImpl iml=new BookServiceImpl();
        iml.setBookMapper(mapper);
        iBookService= iml;
    }

    @After
    public void tearDown() throws Exception {
        sqlSessionmit();
        MybatisSqlSessionFactory.closeSqlsession();
    }


    @Test
    public void resultType3() {
        Book book = iBookService.resultType3();
        System.out.println(book);
    }



}

3. 使用resultType返回List<Map>，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

    @MapKey("id")
       List<Map<String,Object>> resultType4();

• mapper.xml 

  <select id="resultType4" resultType="java.util.Map">
    select book_id,price,book_name from tb_book
  </select>

•  service层

List<Map<String,Object>> resultType4();

•  实现类

    //创建对象
    private BookMapper bookMapper;


    /**
     * 给bookMapper set,get方法
     * @return
     */
    public BookMapper getBookMapper() {
        return bookMapper;
    }

    public void setBookMapper(BookMapper bookMapper) {
        this.bookMapper = bookMapper;
    }
    @Override
    public List<Map<String, Object>> resultType4() {
        return bookMapper.resultType4();
    }

•  使用junit测试

package com.jmh.mybatis.service.impl;

import com.jmh.mybatis.mapper.BookMapper;
import com.jmh.mybatis.model.Book;
import com.jmh.mybatis.model.BookVo;
import com.jmh.mybatis.service.IBookService;
import com.jmh.mybatis.utils.MybatisSqlSessionFactory;
import org.apache.ibatis.annotations.MapKey;
import org.apache.ibatis.session.SqlSession;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import java.util.List;
import java.util.Map;
import java.util.Set;

import static org.junit.Assert.*;

public class DemoTest {
    //获取对象
    private Book book;
    private IBookService iBookService;
    private SqlSession sqlSession;

    @Before
    public void setUp() throws Exception {
        book=new Book();
        sqlSession = MybatisSqlSessionFactory.getSqlsession();
        BookMapper mapper = sqlSession.getMapper(BookMapper.class);
        BookServiceImpl iml=new BookServiceImpl();
        iml.setBookMapper(mapper);
        iBookService= iml;
    }

    @After
    public void tearDown() throws Exception {
        sqlSessionmit();
        MybatisSqlSessionFactory.closeSqlsession();
    }


    @Test
    public void resultType4() {
        List<Map<String, Object>> maps = iBookService.resultType4();
        for (Map<String, Object> map : maps) {
            System.out.println(map);
        }
    }

}

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

•  mapper接口

@MapKey("id")
        Map<String,Object> resultType5();

• mapper.xml 

  <select id="resultType5" resultType="java.util.Map">
    select book_id,price from tb_book
  </select>

•  service层

Map<String,Object> resultType5();

•  实现类

    //创建对象
    private BookMapper bookMapper;


    /**
     * 给bookMapper set,get方法
     * @return
     */
    public BookMapper getBookMapper() {
        return bookMapper;
    }

    public void setBookMapper(BookMapper bookMapper) {
        this.bookMapper = bookMapper;
    }

    @Override
    public Map<String, Object> resultType5() {
        return bookMapper.resultType5();
    }

•  使用junit测试

package com.jmh.mybatis.service.impl;

import com.jmh.mybatis.mapper.BookMapper;
import com.jmh.mybatis.model.Book;
import com.jmh.mybatis.model.BookVo;
import com.jmh.mybatis.service.IBookService;
import com.jmh.mybatis.utils.MybatisSqlSessionFactory;
import org.apache.ibatis.annotations.MapKey;
import org.apache.ibatis.session.SqlSession;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import java.util.List;
import java.util.Map;
import java.util.Set;

import static org.junit.Assert.*;

public class DemoTest {
    //获取对象
    private Book book;
    private IBookService iBookService;
    private SqlSession sqlSession;

    @Before
    public void setUp() throws Exception {
        book=new Book();
        sqlSession = MybatisSqlSessionFactory.getSqlsession();
        BookMapper mapper = sqlSession.getMapper(BookMapper.class);
        BookServiceImpl iml=new BookServiceImpl();
        iml.setBookMapper(mapper);
        iBookService= iml;
    }

    @After
    public void tearDown() throws Exception {
        sqlSessionmit();
        MybatisSqlSessionFactory.closeSqlsession();
}

    @Test
    public void resultType5() {
        Map<String, Object> map = iBookService.resultType5();
        System.out.println(map);
    }
}

---