1.SpringBoot整合Mybatis(CRUD的实现)

准备工具:IDEA   jdk1.8  Navicat for MySQL  Postman

 

一、新建Project

选择依赖:mybatis  Web  Mysql  JDBC

项目结构

pom依赖:

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 3          xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
 4     <modelVersion>4.0.0</modelVersion>
 5     <parent>
 6         <groupId>org.springframework.boot</groupId>
 7         <artifactId>spring-boot-starter-parent</artifactId>
 8         <version>2.1.7.RELEASE</version>
 9         <relativePath/> <!-- lookup parent from repository -->
10     </parent>
11     <groupId>com.beilin</groupId>
12     <artifactId>SpringBoot-Mybatis</artifactId>
13     <version>0.0.1-SNAPSHOT</version>
14     <name>SpringBoot-Mybatis</name>
15     <description>Demo project for Spring Boot</description>
16 
17     <properties>
18         <java.version>1.8</java.version>
19     </properties>
20     <dependencies>
21         <dependency>
22             <groupId>org.springframework.boot</groupId>
23             <artifactId>spring-boot-starter-jdbc</artifactId>
24         </dependency>
25         <dependency>
26             <groupId>org.springframework.boot</groupId>
27             <artifactId>spring-boot-starter-web</artifactId>
28         </dependency>
29 
30         <!--导入mybatis依赖-->
31         <dependency>
32             <groupId>org.mybatis.spring.boot</groupId>
33             <artifactId>mybatis-spring-boot-starter</artifactId>
34             <version>2.1.0</version>
35         </dependency>
36 
37         <!--导入mysql依赖-->
38         <dependency>
39             <groupId>mysql</groupId>
40             <artifactId>mysql-connector-java</artifactId>
41             <version>5.1.47</version>
42         </dependency>
43 
44         <dependency>
45             <groupId>org.springframework.boot</groupId>
46             <artifactId>spring-boot-starter-test</artifactId>
47             <scope>test</scope>
48         </dependency>
49     </dependencies>
50 
51     <build>
52         <plugins>
53             <plugin>
54                 <groupId>org.springframework.boot</groupId>
55                 <artifactId>spring-boot-maven-plugin</artifactId>
56             </plugin>
57         </plugins>
58     </build>
59 
60 </project>
pom.xml

二、创建user表

 

 、项目配置

1 .在com.beilin下创建controller包、mapper包,entity包;在resources文件夹下创建mapping文件夹(用来存放mapper映射的xml文件)

 

 

 2 .添加properties配置文件:application.properties

 1 #配置mybatis
 2 
 3 #配置xml映射路径
 4 mybatis.mapper-locations=classpath:mapping/*.xml
 5 #配置实体类别名
 6 mybatis.type-aliases-package=com.beilin.entity
 7 #开启驼峰命名法
 8 mybatis.configuration.map-underscore-to-camel-case=true
 9 
10 #配置Mysql连接
11 spring.datasource.url=jdbc:mysql://localhost:3306/mybatis?useUnicode=true&characterEncoding=utf8&serverTimezone=UTC
12 spring.datasource.username=root
13 spring.datasource.password=123456
14 spring.datasource.driver-class-name=com.mysql.jdbc.Driver
application.properties

3.在Springboot启动类添加@MapperScan注解

 1 package com.beilin;
 2 
 3 import org.mybatis.spring.annotation.MapperScan;
 4 import org.springframework.boot.SpringApplication;
 5 import org.springframework.boot.autoconfigure.SpringBootApplication;
 6 
 7 @MapperScan(value = "com.beilin.mapper")
 8 @SpringBootApplication
 9 public class SpringbootApplication {
10 
11     public static void main(String[] args) {
12         SpringApplication.run(SpringbootApplication.class, args);
13     }
14 
15 }
SpringbootApplication

四、代码实现

1.实体类User

 1 package com.beilin.entity;
 2 
 3 public class User {
 4     /**
 5      *  name:user实体
 6      */
 7 
 8     //主键id
 9     private int id;
10     //姓名
11     private String name;
12     //年龄
13     private int age;
14 
15     // Get和 Set方法
16     public int getId() {
17         return id;
18     }
19 
20     public void setId(int id) {
21         this.id = id;
22     }
23 
24     public String getName() {
25         return name;
26     }
27 
28     public void setName(String name) {
29         this.name = name;
30     }
31 
32     public int getAge() {
33         return age;
34     }
35 
36     public void setAge(int age) {
37         this.age = age;
38     }
39 }
40 
41 User.java
User.java

2.数据操作层UserMapper

 1 package com.beilin.mapper;
 2 
 3 import com.beilin.entity.User;
 4 
 5 import java.util.List;
 6 
 7 public interface UserMapper {
 8 
 9      //插入
10     public void insert(User user);
11 
12     //根据id删除
13     public void delete(Integer id);
14 
15      //根据user的id修改
16     public void update(User user);
17 
18     //根据id查询
19     public User getById(Integer id);
20 
21     //查询全部
22     public List<User> list();
23 
24 }
UserMapper.java

3.UserMapper映射文件

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
 3 <mapper namespace="com.beilin.mapper.UserMapper">
 4 
 5     <!-- 插入一个user -->
 6     <insert id="insert" parameterType="user">
 7     insert into user(name,age) values(#{name},#{age})
 8     </insert>
 9 
10     <!-- 根据id删除user -->
11     <delete id="delete" parameterType="int">
12     delete  from user where id=#{id}
13     </delete>
14 
15     <!-- 根据id修改user信息 -->
16     <update id="update" parameterType="user">
17     update user set name=#{name},age=#{age} where id=#{id}
18     </update>
19 
20     <!-- 根据id查询 -->
21     <select id="getById" parameterType="int" resultType="user">
22     select * from user where id=#{id}
23     </select>
24 
25     <!-- 查询所有 -->
26     <select id="list" parameterType="int" resultType="user">
27     select * from user
28     </select>
29 
30 </mapper>
UserMapper.xml

4.控制层UserController

 1 package com.beilin.controller;
 2 
 3 import com.beilin.entity.User;
 4 import com.beilin.mapper.UserMapper;
 5 import org.springframework.beans.factory.annotation.Autowired;
 6 import org.springframework.web.bind.annotation.*;
 7 
 8 import java.util.List;
 9 
10 @RestController
11 public class UserController {
12 
13     @Autowired
14     private UserMapper userMapper;
15 
16         //插入user
17     @RequestMapping("/user")
18     public void insert( User user) {
19         userMapper.insert(user);
20     }
21 
22       //根据id删除
23     @RequestMapping("/user1/{id}")
24     public void delete(@PathVariable("id") Integer id) {
25         userMapper.delete(id);
26     }
27         //修改
28     @RequestMapping("/user2/{id}")
29     public void update(User user,@PathVariable("id") Integer id) {
30         userMapper.update(user);
31     }
32 
33      //根据id查询学生
34     @RequestMapping("/user3/{id}")
35     public User getById(@PathVariable("id") Integer id) {
36         User user = userMapper.getById(id);
37         return user;
38     }
39 
40     //查询全部
41     @RequestMapping("/users")
42     public List<User> list(){
43         List<User> users = userMapper.list();
44         return users;
45     }
46 
47 }
UserController.java

 

测试使用PostMan或者直接在浏览器测试

 

过程中所遇到的问题:

报错:org.apache.ibatis.binding.BindingException: Invalid bound statement (not found)

解释:就是说,你的Mapper接口,被SpringBoot注入后,却无法正常的使用mapper.xml的sql;

首先检查下自己的代码是否错误,sql语句是否正确,在此基础上对照下面的解决方法。

这里的可能发生的情况有如下几种:

  1. 接口已经被扫描到,但是代理对象没有找到,即使尝试注入,也是注入一个错误的对象(可能就是null)
  2. 接口已经被扫描到,代理对象找到了,也注入到接口上了,但是调用某个具体方法时,却无法使用(可能别的方法是正常的)

二者报错的结果是一样的,这里就提供几种排查方法:

   1.mapper接口和mapper.xml是否在同一个包(package)下?名字是否一样(仅后缀不同)?

         比如,接口名是UserMapper.java;对应的xml就应该是UserMapper.xml  

   2.mapper.xml的命名空间(namespace)是否跟mapper接口的包名一致?

    比如,你接口的包名是com.beilin.mapper,接口名是UserMapper.java,那么你的mapper.xml的namespace应该是com.beilin.mapper.UserMapper 

  3.接口的方法名,与xml中的一条sql标签的id一致 

    比如,接口的方法List<User> GetById();那么,对应的xml里面一定有一条是<select id="GetByIdparameterType="int" resultType="user">****</select>  

  4.如果接口中的返回值List集合(不知道其他集合也是),那么xml里面的配置,尽量用resultMap(保证resultMap配置正确),不要用resultType

  5.最后,在编译后,到接口所在目录看一看,很有可能是没有生产对应的xml文件,因为maven默认是不编译的,因此,你需要在你的pom.xml的<build></build>里面,加这么一段:

 

1 <resources>
2             <resource>
3                 <directory>src/main/java</directory>
4                 <includes>
5                     <include>**/*.xml</include>
6                 </includes>
7                 <filtering>true</filtering>
8             </resource>
9  </resources>
resources

 

 

 

 

 

 

 

 

1.SpringBoot整合Mybatis(CRUD的实现)

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