mybatis-映射文件

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基本介绍
环境

基本介绍

环境

/*
 Navicat Premium Data Transfer

 Source Server         : school
 Source Server Type    : MySQL
 Source Server Version : 80022
 Source Host           : localhost:3306
 Source Schema         : school

 Target Server Type    : MySQL
 Target Server Version : 80022
 File Encoding         : 65001

 Date: 15/11/2021 19:49:16
*/

SET NAMES utf8mb4;
SET FOREIGN_KEY_CHECKS = 0;

-- ----------------------------
-- Table structure for grade
-- ----------------------------
DROP TABLE IF EXISTS `grade`;
CREATE TABLE `grade`  (
  `gradeId` int(0) NOT NULL AUTO_INCREMENT,
  `gradeName` varchar(255) CHARACTER SET utf8 COLLATE utf8_bin NOT NULL,
  PRIMARY KEY (`gradeId`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 2 CHARACTER SET = utf8 COLLATE = utf8_bin ROW_FORMAT = Dynamic;

-- ----------------------------
-- Records of grade
-- ----------------------------
INSERT INTO `grade` VALUES (1, 'S1');
INSERT INTO `grade` VALUES (2, 'Y1');

SET FOREIGN_KEY_CHECKS = 1;

/*
 Navicat Premium Data Transfer

 Source Server         : school
 Source Server Type    : MySQL
 Source Server Version : 80022
 Source Host           : localhost:3306
 Source Schema         : school

 Target Server Type    : MySQL
 Target Server Version : 80022
 File Encoding         : 65001

 Date: 15/11/2021 19:49:31
*/

SET NAMES utf8mb4;
SET FOREIGN_KEY_CHECKS = 0;

-- ----------------------------
-- Table structure for student
-- ----------------------------
DROP TABLE IF EXISTS `student`;
CREATE TABLE `student`  (
  `stuId` int(0) NOT NULL AUTO_INCREMENT,
  `stuName` varchar(255) CHARACTER SET utf8 COLLATE utf8_bin NULL DEFAULT NULL,
  `stuAge` int(0) NULL DEFAULT NULL,
  `stuBirth` varchar(255) CHARACTER SET utf8 COLLATE utf8_bin NULL DEFAULT NULL,
  `gradeId` int(0) NOT NULL,
  PRIMARY KEY (`stuId`) USING BTREE,
  INDEX `gradeId`(`gradeId`) USING BTREE,
  CONSTRAINT `student_ibfk_1` FOREIGN KEY (`gradeId`) REFERENCES `grade` (`gradeId`) ON DELETE RESTRICT ON UPDATE RESTRICT
) ENGINE = InnoDB AUTO_INCREMENT = 7 CHARACTER SET = utf8 COLLATE = utf8_bin ROW_FORMAT = Dynamic;

-- ----------------------------
-- Records of student
-- ----------------------------
INSERT INTO `student` VALUES (1, '张三', 18, '2010-10-02', 1);
INSERT INTO `student` VALUES (2, '李四', 18, '2002-10-02', 2);
INSERT INTO `student` VALUES (3, '王五', 16, '2005-10-02', 2);
INSERT INTO `student` VALUES (5, '赵六', 22, '2020-10-27 00:00:00.0', 1);
INSERT INTO `student` VALUES (6, '赵六', 22, '2020-10-27 00:00:00.0', 1);
INSERT INTO `student` VALUES (7, '田七', 22, '2021-05-18 17:13:40', 2);

SET FOREIGN_KEY_CHECKS = 1;

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>

    <properties resource="dbconfig.properties"/>
    
    <settings>
        <!--开启驼峰命名自动映射-->
        <setting name="mapUnderscoreToCamelCase" value="true"/>
    </settings>

    <typeAliases>
        <package name="com.fly.entity"/>
    </typeAliases>

    <environments default="development">
        <!--每个environment是一个环境，default属性指向使用哪个环境-->
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${db.driver}"/>
                <property name="url" value="${db.url}"/>
                <property name="username" value="${db.username}"/>
                <property name="password" value="${db.password}"/>
            </dataSource>
        </environment>
    </environments>

    <mappers>
        <!--mybatis-config.xml-->
       <mapper resource="mapper/GradeMapper.xml"/>
    </mappers>

</configuration>

db.driver=com.mysql.cj.jdbc.Driver
db.url=jdbc:mysql://localhost:3306/school?useUnicode=true&characterEncoding=utf-8&useSSL=false&serverTimezone=GMT%2B8&allowPublicKeyRetrieval=true
db.username=root
db.password=123456

dbconfig.properties

package com.fly.entity;

import java.util.Date;

/**
 * @author 26414
 */
public class Student {

  private Integer stuId;
  private String stuName;
  private Integer stuAge;
  private Date stuBirth;

  @Override
  public String toString() {
    return "Student{" +
            "stuId=" + stuId +
            ", stuName='" + stuName + '\'' +
            ", stuAge=" + stuAge +
            ", stuBirth=" + stuBirth +
            ", grade=" + grade +
            '}';
  }

  private Grade grade;

  public Integer getStuId() {
    return stuId;
  }

  public void setStuId(Integer stuId) {
    this.stuId = stuId;
  }

  public String getStuName() {
    return stuName;
  }

  public void setStuName(String stuName) {
    this.stuName = stuName;
  }

  public Integer getStuAge() {
    return stuAge;
  }

  public void setStuAge(Integer stuAge) {
    this.stuAge = stuAge;
  }

  public Date getStuBirth() {
    return stuBirth;
  }

  public void setStuBirth(Date stuBirth) {
    this.stuBirth = stuBirth;
  }

  public Grade getGrade() {
    return grade;
  }

  public void setGrade(Grade grade) {
    this.grade = grade;
  }
}

package com.fly.dao;

import com.fly.entity.Grade;

/**
 * @author 26414
 */
public interface GradeMapper {

  /**
   * 根据id查询年级
   * @param gradeId 年级id
   * @return gradeId对应的年级
   */
  Grade getGradeById(Integer gradeId);

}

insert

 /**
   * GradeMapper
   * 添加年级
   * @param grade 年级对象
   */
  void insert(Grade grade);

   <!--GradeMapper.xml-->
    <insert id="insert">
        insert into grade values(null,#{gradeName})
    </insert>

  @Test
  public void test4() throws IOException {
    String resource = "mybatis-config.xml";
    InputStream inputStream = Resources.getResourceAsStream(resource);
    SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    try (SqlSession sqlSession = sqlSessionFactory.openSession()) {
      GradeMapper mapper = sqlSession.getMapper(GradeMapper.class);
      Grade grade = new Grade();
      grade.setGradeName("一年级");
      mapper.insert(grade);
      //手动提交事务
      sqlSession.commit();
    }
  }

返回主键

<!--GradeMapper.xml-->
    <insert id="insert" useGeneratedKeys="true" keyProperty="gradeId">
        insert into grade values(null,#{gradeName})
    </insert>

 @Test
  public void test4() throws IOException {
    String resource = "mybatis-config.xml";
    InputStream inputStream = Resources.getResourceAsStream(resource);
    SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    try (SqlSession sqlSession = sqlSessionFactory.openSession()) {
      GradeMapper mapper = sqlSession.getMapper(GradeMapper.class);
      Grade grade = new Grade();
      grade.setGradeName("二年级");
      mapper.insert(grade);
      //手动提交事务
      sqlSession.commit();
      System.out.println("grade.getGradeId() = " + grade.getGradeId());
    }
  }

delete

 /**
   * GradeMapper
   * 根据id删除年级
   * @param gradeId 年级id
   */
  void deleteById(Integer gradeId);

   <!--GradeMapper.xml-->
    <delete id="deleteById">
        delete from grade where gradeId = #{gradeId}
    </delete>

 @Test
  public void test5() throws IOException {
    String resource = "mybatis-config.xml";
    InputStream inputStream = Resources.getResourceAsStream(resource);
    SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    try (SqlSession sqlSession = sqlSessionFactory.openSession()) {
      GradeMapper mapper = sqlSession.getMapper(GradeMapper.class);
      mapper.deleteById(8);
      //手动提交事务
      sqlSession.commit();
    }
  }

update

 /**
   * GradeMapper
   * @param grade 年级对象
   */
  void updateById(Grade grade);

  <!--GradeMapper.xml-->
    <update id="updateById">
        update grade set gradeName = #{gradeName} where gradeId = #{gradeId}
    </update>

 @Test
  public void test6() throws IOException {
    String resource = "mybatis-config.xml";
    InputStream inputStream = Resources.getResourceAsStream(resource);
    SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    try (SqlSession sqlSession = sqlSessionFactory.openSession()) {
      GradeMapper mapper = sqlSession.getMapper(GradeMapper.class);
      Grade grade = new Grade();
      grade.setGradeId(6);
      grade.setGradeName("一年级...");
      mapper.updateById(grade);
      //手动提交事务
      sqlSession.commit();
    }
  }

参数处理

单个参数

MyBatis可直接使用这个参数，不需要经过任何处理。

多个参数

会被MyBatis重新包装成一个Map传入。Map的key是param1，param2，arg0，arg1…，值就是参数的值。

package com.fly.dao;

import com.fly.entity.Student;

/**
 * @author 26414
 */
public interface StudentMapper {

  /**
   * StudentMapper
   * 根据姓名和年级查询学生
   * @param stuName 学生姓名
   * @param stuAge 学生年龄
   * @return 学生
   */
  Student selectByNameAndAge(String stuName,Integer stuAge);

}

 <!--StudentMapper.xml-->
    <select id="selectByNameAndAge" resultType="com.fly.entity.Student">
        select * from student where stuName = #{arg0} and stuAge = #{arg1}
    </select>

  <mappers>
        <!--mybatis-config.xml-->
        <mapper resource="mapper/GradeMapper.xml"/>
        <mapper resource="mapper/StudentMapper.xml"/>
    </mappers>

  @Test
  public void test1() throws IOException {
    String resource = "mybatis-config.xml";
    InputStream inputStream = Resources.getResourceAsStream(resource);
    SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    try (SqlSession sqlSession = sqlSessionFactory.openSession()) {
      StudentMapper mapper = sqlSession.getMapper(StudentMapper.class);
      Student student = mapper.selectByNameAndAge("张三", 18);
      System.out.println("student = " + student);
      //手动提交事务
      sqlSession.commit();
    }
  }

···xml

<select id="selectByNameAndAge" resultType="com.fly.entity.Student">
    select * from student where stuName = #{param1} and stuAge = #{param2}
</select>

![](https://www.www.zyiz.net/i/l/?n=20&i=blog/2276392/202111/2276392-20211115234705480-1575124065.png)
###命名参数
为参数使用@Param起一个名字，MyBatis就会将这些参数封装进map中，key就是我们自己指定的名字
```java
  /**
   * StudentMapper
   * 根据姓名和年级查询学生
   * @param stuName 学生姓名
   * @param stuAge 学生年龄
   * @return 学生
   */
  Student selectByNameAndAge(@Param("stuName") String stuName, @Param("stuAge") Integer stuAge);

 <!--StudentMapper.xml-->
    <select id="selectByNameAndAge" resultType="com.fly.entity.Student">
        select * from student where stuName = #{stuName} and stuAge = #{stuAge}
    </select>

${}

{key}：获取参数的值，预编译到SQL中。安全。

${key}：获取参数的值，拼接到SQL中。有SQL注入问题。

select

映射

自动映射

1）autoMappingBehavior默认是PARTIAL，开启自动映射的功能。唯一的要求是列名和javaBean属性名一致
2）如果autoMappingBehavior设置为null则会取消自动映射
3）数据库字段命名规范，POJO属性符合驼峰命名法，如A_COLUMNaColumn，我们可以开启自动驼峰命名规则映射功能，mapUnderscoreToCamelCase=true。

自定义映射

association

/**
   * StudentMapper
   * 根据id查学生
   * @param stuId 学生id
   * @return 学生对象
   */
  Student selectById(@Param("stuId") Integer stuId);

 <resultMap id="fullResultMap" type="student">
        <id column="stuId" property="stuId"/>
        <result column="stuName" property="stuName"/>
        <result column="stuAge" property="stuAge"/>
        <result column="stuBirth" property="stuBirth"/>
        <association property="grade" javaType="grade">
            <id column="gradeId" property="gradeId"/>
            <result column="gradeName" property="gradeName"/>
        </association>
    </resultMap>
<!--StudentMapper.xml-->
    <select id="selectById" resultMap="fullResultMap">
        SELECT * FROM student s, grade g where stuId = #{stuId} and
            s.gradeId = g.gradeId
    </select>

 @Test
  public void test2() throws IOException {
    String resource = "mybatis-config.xml";
    InputStream inputStream = Resources.getResourceAsStream(resource);
    SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    try (SqlSession sqlSession = sqlSessionFactory.openSession()) {
      StudentMapper mapper = sqlSession.getMapper(StudentMapper.class);
      Student student = mapper.selectById(1);
      System.out.println("student = " + student);
      //手动提交事务
      sqlSession.commit();
    }
  }

#######分段查询

 /**
   * StudentMapper
   * 根据id查学生
   * @param stuId 学生id
   * @return 学生对象
   */
  Student selectByIdAndStep(@Param("stuId") Integer stuId);

 <resultMap id="fullResultMapByStep" type="student">
        <id column="stuId" property="stuId"/>
        <result column="stuName" property="stuName"/>
        <result column="stuAge" property="stuAge"/>
        <result column="stuBirth" property="stuBirth"/>
        <association property="grade"
                     select="com.fly.dao.GradeMapper.getGradeById"
                     column="gradeId"/>
    </resultMap>
<!--StudentMapper.xml-->
    <select id="selectByIdAndStep" resultMap="fullResultMapByStep">
        select * from student where stuId = #{stuId}
    </select>

  @Test
  public void test3() throws IOException {
    String resource = "mybatis-config.xml";
    InputStream inputStream = Resources.getResourceAsStream(resource);
    SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    try (SqlSession sqlSession = sqlSessionFactory.openSession()) {
      StudentMapper mapper = sqlSession.getMapper(StudentMapper.class);
      Student student = mapper.selectByIdAndStep(1);
      System.out.println("student = " + student);
      //手动提交事务
      sqlSession.commit();
    }
  }

#######延迟加载

   <settings>
        <!--开启驼峰命名自动映射-->
        <!--mybatis-config.xml-->
        <setting name="mapUnderscoreToCamelCase" value="true"/>
        <setting name="lazyLoadingEnabled" value="trie"/>
        <setting name="aggressiveLazyLoading" value="false"/>
    </settings>

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Java教程

mybatis-映射文件

基本介绍

环境

dbconfig.properties

insert

返回主键

delete

update

参数处理

单个参数

多个参数

${}

{key}：获取参数的值，预编译到SQL中。安全。

select

映射

自动映射

自定义映射

association

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