【Mybatis从入门到实战教程】第十章 Mybatis 注解开发

分手后的思念是犯贱 2024-04-28 13:21 10阅读 0赞

## 十、Mybatis 注解开发 ##

### 10.1 什么是注解开发 ###

Mybatis最初配置信息是基于XML，映射语句(SQL)也是定义在 XML 中的。而到了 MyBatis 3提供了新的基于注解的配置。使用注解开发方式，可以减少编写 Mapper 映射文件。

### 10.2 常用注解说明 ###

<table> 
 <thead> 
  <tr> 
   <th>注解</th> 
   <th>描述</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td>@Insert</td> 
   <td>配置新增</td> 
  </tr> 
  <tr> 
   <td>@Update</td> 
   <td>配置更新</td> 
  </tr> 
  <tr> 
   <td>@Delete</td> 
   <td>配置删除</td> 
  </tr> 
  <tr> 
   <td>@Select</td> 
   <td>配置查询</td> 
  </tr> 
  <tr> 
   <td>@Options</td> 
   <td>配置主键返回，关闭二级缓存等功能</td> 
  </tr> 
  <tr> 
   <td>@Result</td> 
   <td>结果集封装</td> 
  </tr> 
  <tr> 
   <td>@Results</td> 
   <td>与@Result 一起使用，封装多个结果集</td> 
  </tr> 
  <tr> 
   <td>@ResultMap</td> 
   <td>引用@Results 定义的封装</td> 
  </tr> 
  <tr> 
   <td>@One</td> 
   <td>一对一结果集封装</td> 
  </tr> 
  <tr> 
   <td>@Many</td> 
   <td>一对多结果集封装</td> 
  </tr> 
  <tr> 
   <td>@SelectProvider</td> 
   <td>动态 SQL 映射</td> 
  </tr> 
  <tr> 
   <td>@CacheNamespace</td> 
   <td>二级缓存</td> 
  </tr> 
  <tr> 
   <td>@Param</td> 
   <td>输入多参数</td> 
  </tr> 
  <tr> 
   <td>@Mapper</td> 
   <td>把mapper这个DAO交給Spring管理，整合用到</td> 
  </tr> 
 </tbody> 
</table>

### 10.3 实体类 ###

#### 10.3.1 部门类 ####

public class Dept {
    
        private Integer deptno;
        private String dname;
        private String loc;
    
        public Integer getDeptno() {
            return deptno;
        }
    
        public void setDeptno(Integer deptno) {
            this.deptno = deptno;
        }
    
        public String getDname() {
            return dname;
        }
    
        public void setDname(String dname) {
            this.dname = dname;
        }
    
        public String getLoc() {
            return loc;
        }
    
        public void setLoc(String loc) {
            this.loc = loc;
        }
    
        @Override
        public String toString() {
            return "Dept{" +
                    "deptno=" + deptno +
                    ", dname='" + dname + '\'' +
                    ", loc='" + loc + '\'' +
                    '}';
        }
    }

#### 10.3.2 员工类 ####

public class Emp {
    
        private Integer empno;
        private String ename;
        private String job;
        private Integer mgr;
        private Date hiredate;
        private Double sal;
        private Double comm;
        private Integer deptno;
        private Dept dept;
    
        public Integer getEmpno() {
            return empno;
        }
    
        public void setEmpno(Integer empno) {
            this.empno = empno;
        }
    
        public String getEname() {
            return ename;
        }
    
        public void setEname(String ename) {
            this.ename = ename;
        }
    
        public String getJob() {
            return job;
        }
    
        public void setJob(String job) {
            this.job = job;
        }
    
        public Integer getMgr() {
            return mgr;
        }
    
        public void setMgr(Integer mgr) {
            this.mgr = mgr;
        }
    
        public Date getHiredate() {
            return hiredate;
        }
    
        public void setHiredate(Date hiredate) {
            this.hiredate = hiredate;
        }
    
        public Double getSal() {
            return sal;
        }
    
        public void setSal(Double sal) {
            this.sal = sal;
        }
    
        public Double getComm() {
            return comm;
        }
    
        public void setComm(Double comm) {
            this.comm = comm;
        }
    
        public Integer getDeptno() {
            return deptno;
        }
    
        public void setDeptno(Integer deptno) {
            this.deptno = deptno;
        }
    
        public Dept getDept() {
            return dept;
        }
    
        public void setDept(Dept dept) {
            this.dept = dept;
        }
    
        @Override
        public String toString() {
            return "Emp{" +
                    "empno=" + empno +
                    ", ename='" + ename + '\'' +
                    ", job='" + job + '\'' +
                    ", mgr=" + mgr +
                    ", hiredate=" + hiredate +
                    ", sal=" + sal +
                    ", comm=" + comm +
                    ", deptno=" + deptno +
                    ", dept=" + dept +
                    '}';
        }
    }

### 10.4 单表增删改差 ###

#### 10.4.1 mapper接口 ####

public interface DeptMapper {
        @Select("select deptno,dname,loc from dept")
        List<Dept> select();
    
        @Select("select deptno,dname,loc from dept where deptno = #{deptno}")
        Dept selectById(Integer deptno);
    
        @Insert("insert into dept(dname,loc) values (#{dname}, #{loc})")
        @Options(useGeneratedKeys = true, keyProperty = "deptno", keyColumn = "deptno")
        void insert(Dept dept);
    
        @Update("update dept set dname = #{dname},loc=#{loc} where deptno = #{deptno}")
        void update(Dept dept);
    
        @Delete("delete from dept where deptno=#{deptno}")
        void delete(Integer deptno);
    }

#### 10.4.2 测试 ####

public class AnnotationTest {
    
        @Test
        public void testSelect() {
            SqlSession sqlSession = MybatisUtil.getSession();
    
            DeptMapper deptMapper = sqlSession.getMapper(DeptMapper.class);
            List<Dept> list = deptMapper.select();
            for (Dept dept : list) {
                System.out.println(dept);
            }
    
            sqlSession.close();
        }
    
        @Test
        public void testSelectById() {
            SqlSession sqlSession = MybatisUtil.getSession();
    
            DeptMapper deptMapper = sqlSession.getMapper(DeptMapper.class);
            Dept dept = deptMapper.selectById(10);
            System.out.println(dept);
    
            sqlSession.close();
        }
    
        @Test
        public void testInsert() {
            SqlSession sqlSession = MybatisUtil.getSession();
    
            DeptMapper deptMapper = sqlSession.getMapper(DeptMapper.class);
            Dept dept = new Dept();
            dept.setDname("aa");
            dept.setLoc("aa");
            deptMapper.insert(dept);
            sqlSession.commit();
            System.out.println("主键:" + dept.getDeptno());
    
            sqlSession.close();
        }
    
        @Test
        public void testUpdate() {
            SqlSession sqlSession = MybatisUtil.getSession();
    
            DeptMapper deptMapper = sqlSession.getMapper(DeptMapper.class);
            Dept dept = new Dept();
            dept.setDeptno(41);
            dept.setDname("bb");
            dept.setLoc("bb");
            deptMapper.update(dept);
            sqlSession.commit();
    
            sqlSession.close();
        }
    
        @Test
        public void testDelete() {
            SqlSession sqlSession = MybatisUtil.getSession();
    
            DeptMapper deptMapper = sqlSession.getMapper(DeptMapper.class);
            deptMapper.delete(41);
            sqlSession.commit();
    
            sqlSession.close();
        }
    }

### 10.5 一对一关系映射 ###

#### 10.5.1 mapper接口 ####

public interface EmpMapper {
        /*
         * 手动映射resultMap标签
         * @Results + @Result注解替代
         * @Results = resultMap标签
         * @Result = resultMap标签的子标签id和result
         */
        @Select("select empno,ename,job,mgr,hiredate,sal,comm,deptno from emp")
        @Results(id = "selectResultMap",
                 value = {
                     @Result(id = true, column = "empno", property = "empno"),
                     @Result(column = "ename", property = "ename"),
                     @Result(column = "job", property = "job"),
                     @Result(column = "mgr", property = "mgr"),
                     @Result(column = "hiredate", property = "hiredate"),
                     @Result(column = "sal", property = "sal"),
                     @Result(column = "comm", property = "comm"),
                     @Result(column = "deptno", property = "deptno"),
                     @Result(column = "deptno", property = "dept", javaType = Dept.class,
                             one = @One(select = "com.newcapec.dao.DeptDao.selectById", fetchType = FetchType.LAZY))
                 })
        List<Emp> select();
    
        @Select("select empno,ename,job,mgr,hiredate,sal,comm,deptno from emp where empno=#{empno}")
        @ResultMap("selectResultMap")
        Emp selectById(Integer empno);
    }

#### 10.5.2 测试 ####

@Test
    public void testSelectEmp() {
        SqlSession sqlSession = MybatisUtil.getSession();
    
        EmpMapper empMapper = sqlSession.getMapper(EmpMapper.class);
    
        List<Emp> empList = empMapper.select();
        for (Emp emp : empList) {
            System.out.println(emp);
        }
        sqlSession.close();
    }
    
    @Test
    public void testSelectEmpById() {
        SqlSession sqlSession = MybatisUtil.getSession();
    
        EmpMapper empMapper = sqlSession.getMapper(EmpMapper.class);
    
        Emp emp = empMapper.selectById(7369);
        System.out.println(emp);
        sqlSession.close();
    }