mybatis使用注解的方式执行sql语句

浅浅的花香味﹌ 2022-01-06 01:13 542阅读 0赞

#### mybatis在不使用注解时 SQL语句都是写在.xml配置文件中 ####

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<?xml version="1.0" encoding="UTF-8" ?>
    <!DOCTYPE mapper
            PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
            "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
    <mapper namespace="com.gx.mapper.EmployeeMapper">
        //简单的查询语句
        <select id="findAll" resultType="emp">
          /*标准sql语句*/
          select * from emp 
        </select>
      
    </mapper>

**使用注解模式时SQL语句直接在接口中的方法上的注解即可**  
.xml配置文件注意namspace即可，当然也可以不使用改配置文件，但是那就就在每个注解方法中都要加上一句话稍微费事点，个人建议还是使用namespace属性比较方便

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#### 接口文件： ####

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package com.gx.mapper;
    
    import com.gx.vo.Dept;
    import com.gx.vo.Employee;
    import org.apache.ibatis.annotations.One;
    import org.apache.ibatis.annotations.Result;
    import org.apache.ibatis.annotations.Results;
    import org.apache.ibatis.annotations.Select;
    import org.apache.ibatis.mapping.FetchType;
    
    import java.util.List;
    
    public interface EmployeeMapper { 
        //Dao中定义的抽象方法要映射文件中的id值匹配起来，映射中的的参数就是此处方法的参数
        @Select("select * from emp")
        public List<Employee> findAll();
    
        @Select("select * from emp where deptno = #{dno}")
        @Results({ 
                @Result(id=true,column="id",property="id"),
                @Result(column = "ename",property = "ename"),
                @Result(column = "esex",property = "esex"),
                @Result(column = "esalary",property = "esalary"),
                @Result(column = "dno",property = "dept",javaType = Dept.class,
                one = @One(select = "com.gx.mapper.DeptMapper.selectDeptByDeptno",fetchType = FetchType.LAZY)),
        })
    
        public List<Employee> findAllByDeptno(int dno);
    
        public List<Employee>  findAllByDept(Employee emp);
    }

#### 测试文件： ####

**为了以后方便直接把测试文件的算是头部封装在了MySqlSessionFactory类中了使用时直接调用即可**  
MySqlSessionFactory 文件：

package com.gx.util;
    
    import org.apache.ibatis.io.Resources;
    import org.apache.ibatis.session.SqlSession;
    import org.apache.ibatis.session.SqlSessionFactory;
    import org.apache.ibatis.session.SqlSessionFactoryBuilder;
    
    import java.io.IOException;
    import java.io.InputStream;
    
    public class MySqlSessionFactory { 
        public static SqlSession getSqlSession() { 
            InputStream input = null;
            SqlSessionFactory sqlSessionFactory = null;
            SqlSession sqlSession = null;
            try { 
                //1.定位MyBatis的主配置文件
                input = Resources.getResourceAsStream("mybatis-config.xml");
            } catch (IOException e) { 
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            //2.根据配置文件创建SqlSessionFactory
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(input);
            //3.使用SqlSessionFactory生产SqlSession
            sqlSession = sqlSessionFactory.openSession();
    
            return sqlSession;
        }
    }

测试文件EmployeeTest

package com.gx.test;
    
    import com.gx.mapper.EmployeeMapper;
    import com.gx.util.MySqlSessionFactory;
    import com.gx.vo.Employee;
    import org.apache.ibatis.session.SqlSession;
    
    import java.util.ArrayList;
    import java.util.List;
    
    public class EmployeeTest { 
        public static void main(String[] args) { 
            SqlSession sqlSession = MySqlSessionFactory.getSqlSession();
            try { 
    
                findAll(sqlSession);
                //测试添加
                //insert(sqlSession);
                //findAllByDeptno(sqlSession);
    // findAllByDept(sqlSession);
                //提交
                sqlSession.commit();
            }catch (Exception e) { 
                // TODO: handle exception
                e.printStackTrace();
                //如果出现了异常则回滚
                if(sqlSession!=null) { 
                    sqlSession.rollback();//回滚
                }
    
            }finally { 
                //关闭sqlSession
                if(sqlSession!=null) { 
                    sqlSession.close();
                }
            }
        }
    
        private static void findAll(SqlSession sqlSession) { 
            EmployeeMapper empMapper = sqlSession.getMapper(EmployeeMapper.class);//通过反射得到对象
            List<Employee> list = empMapper.findAll();
            for(Employee yg : list) { 
                System.out.println(yg.getId()+" "+yg.getEname()+" "+yg.getEsex()+" "+ yg.getEsalary()
                        +" "+yg.getDno());
               /* if(yg.getDept()!=null) { System.out.println(" 对应的部门信息："+yg.getDept().getDno()+" "+yg.getDept().getDname()+" "+yg.getDept().getDcity()); }*/
            }
        }
    
        public static void insert(SqlSession sqlSession) { 
            int reusult=0;
    
            Employee emp = new Employee();
            emp.setEname("赵彬");
            emp.setEsex("男");
            emp.setEsalary(1000.1);
            emp.setDno(1001);
            reusult = sqlSession.insert("com.gx.mapper.EmpMapper.insertEmp",emp);
            System.out.println("添加的结果："+reusult);
        }
    
        public static void findAllByDept(SqlSession sqlSession) { 
            //通过反射得到EmpMapper接口的对象
            EmployeeMapper empMapper = sqlSession.getMapper(EmployeeMapper.class);
            Employee e = new Employee();
            //e.setEname("I");
            //e.setDeptno(20);
            List<Integer> l = new ArrayList<Integer>();
            l.add(1002);
            //l.add(20);
            e.setDeptnos(l);
            List<Employee> list = empMapper.findAllByDeptno(10);
            for(Employee emp : list) { 
                System.out.println(emp.getId()+" "+emp.getEname()+" "+emp.getEsex()+" "+emp.getEsalary()+" "+emp.getDno());
            }
        }
    }

这种注解方式就是把原本写在.xml配置文件中的sql语句放在了接口方法中的注解上去执行sql，实际上完成的都是相同的方法

[20190624104646538.png]: /images/20211228/8b18bf112de6403e955ade99f15b9606.png
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