mybatis中注解映射SQL示例代码

最新推荐文章于 2025-05-17 17:53:10 发布

转载最新推荐文章于 2025-05-17 17:53:10 发布 · 263 阅读

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原文链接：https://juejin.im/post/5c0408f5f265da617573816c

文章标签：

#java

本文深入解析MyBatis中的注解使用，包括@Insert、@Update、@Delete、@Select等注解的详细说明及示例代码。同时介绍了如何通过注解实现动态SQL和结果映射，以及如何定义结果映射文件来避免重复编写查询方法。

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注解@Insert @Update @Select @ Delete

public interface StudentMapper

{

 @Insert("insert into student (stud_id, name, email, addr_id, phone)values(#{studId},#{name},#{email},#{address.addrId},#{phone})")

int insertStudent(Student student);

}

public interface StudentMapper

{

@Insert("insert into student (name,email,addr_id,phone)values(#{name},#{email},#{address.addrId},#{phone})")

@Options(useGeneratedKeys=true,keyProperty="studId")

int insertStudent(Student student);

}

public interface StudentMapper

{

@Insert("insert into student (name,email,addr_id,phone)values(#{name},#{email},#{address.addrId},#{phone})")

@SelectKey(statement="select stud_id_seq.nextval from dual",keyProperty="studId",resultType=int.calss,before=true)

int insertStudent(Student student);

}

@Update("update students set name=#{name},email=#{email}")

int updateStudent(Student student);

@Delete("delete form students where stud_id=#{studId}")

int deleteStudent(int studId)

@Select("select name,email,phone from students where stud_id=#{studId}")

Student findStudentById(Integer studId);

`结果注解`

@Select("select name,email,phone from students where stud_id=#{studId}")

@Results({

@Result(id=true,column="stud_id",property="studId"),

@Result(column="name",property="name"),

@Result(column="email",property="email"),

@Result(column="phone",property="phone")

})

Student findStudentById(Integer studId);

结果注解有一个缺点，就是在一个查询方法前面都要写一遍，不能重用。解决这个问题方案是：

定义一份结果映射文件如下所示：

<mapper namespace="com.mybatis3.mappers.StudentMapper">

<resultMap type="Student" id="StudentResult">

.......

</resultMap>

@Select("select name,email,phone from students where stud_id=#{studId}")

@ResultMap("com.mybatis3.mappers.StudentMapper.StudentResult")

Student findStudentById(Integer studId);

动态Sql的注解

对于动态sql，mybatis提供了不同的注解，@InsertProvider @UpdateProvider @DeleteProvider @SelectProvider
用法如下所示：

首先创建一个provider类：

public class SqlProvider

{

public String findTutorById(int tutorId)

{

return "select tutorId,name,email from tutors where tutorId="+tutorId;

}

使用provider类：

@SelectProvider(type=SqlProvider.class,method="findTutorById")

Tutor findTutorById(int tutorId);

但是使用字符串连接创建sql语句容易出现问题，所以mybatis提供了一个SQL工具，简化了构建动态Sql的方式；

public class SqlProvider

{

public String findTutorById(int tutorId)

{

return new SQL(){{

SELECT("tutorid,name,email")

FROM("tutors")

WHERE("tutorid="+tutorId)

}}.toString();

}

或者

public class SqlProvider

{

public String findTutorById()

{

return new SQL(){{

SELECT("tutorid,name,email")

FROM("tutors")

WHERE("tutorid=#{tutorId}")

}}.toString();

}}

文章摘自：

www.jb51.net/article/121…

转载于:https://juejin.im/post/5c0408f5f265da617573816c