为方便初始化一个SpringBoot项目，可以利用Spring Initializr（https://start.spring.io/） 初始化一个项目
SpringBoot + Mybatis 项目搭建
01 添加依赖包
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.7.15</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.itest</groupId>
<artifactId>springboot-demo</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>springboot-demo</name>
<description>Demo project for Spring Boot</description>
<properties>
<java.version>1.8</java.version>
<druid-version>1.2.8</druid-version>
<mysql-connector-java.version>5.1.18</mysql-connector-java.version>
<fastjson.version>1.2.83</fastjson.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.mybatis.spring.boot</groupId>
<artifactId>mybatis-spring-boot-starter</artifactId>
<version>2.3.1</version>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-devtools</artifactId>
<scope>runtime</scope>
<optional>true</optional>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<scope>runtime</scope>
<version>${mysql-connector-java.version}</version>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.mybatis.spring.boot</groupId>
<artifactId>mybatis-spring-boot-starter-test</artifactId>
<version>2.3.1</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>druid</artifactId>
<version>${druid-version}</version>
</dependency>
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>fastjson</artifactId>
<version>${fastjson.version}</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
02 SpringBoot配置 和 数据库配置
SpringBoot配置文件为application.yaml / application.properties / application*.yml 任意一种格式或者命名都可，YAML文件格式是Spring Boot支持的一种JSON超集文件格式，以数据为中心，更简洁直观
本项目命名为application.yaml，内容如下：
spring:
datasource:
username: xxx
password: xxxxxx
url: jdbc:mysql://itest.ren:3306/testDS?useUnicode=true&characterEncoding=UTF-8&characterSetResults=UTF-8&zeroDateTimeBehavior=convertToNull
driver-class-name: com.mysql.jdbc.Driver
type: com.alibaba.druid.pool.DruidDataSource
initialSize: 5
minIdle: 5
maxActive: 20
maxWait: 60000
timeBetweenEvictionRunsMillis: 60000
minEvictableIdleTimeMillis: 300000
validationQuery: SELECT 1 FROM emp
testWhileIdle: true
testOnBorrow: false
testOnReturn: false
poolPreparedStatements: true
# ?????????filters,??????sql??????wall??????
filters: stat,wall,log4j
maxPoolPreparedStatementPerConnectionSize: 20
userGlobalDataSourceStat: true
connectionProperties: druid.stat.mergeSql=true;druid.stat.slowSqlMillis=500
server:
port: 9090
mybatis:
# config-location: classpath:mybatis/mybatis-config.xml
mapper-locations: classpath:mappers/*.xml
03 编写Mybatis代码，生成表 -> pojo -> mapper接口 -> Mapper.xml
需求：使用mybatis，根据ID查询表中的数据
3-1 表结构信息：
CREATE TABLE `emp` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`name` varchar(50) DEFAULT NULL,
`job` varchar(50) DEFAULT NULL,
`salary` double DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=6 DEFAULT CHARSET=utf8
3-2 pojo
编写/生成对应表字段的实体类，并生成getter/setter方法
package com.itest.springbootdemo.pojo;
public class Emp {
//1.声明实体类中的属性
private Integer id;
private String name;
private String job;
private Double salary;
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getJob() {
return job;
}
public void setJob(String job) {
this.job = job;
}
public Double getSalary() {
return salary;
}
public void setSalary(Double salary) {
this.salary = salary;
}
@Override
public String toString() {
return "Emp{" +
"id=" + id +
", name='" + name + '\'' +
", job='" + job + '\'' +
", salary=" + salary +
'}';
}
}
3-3 mapper interface
企业中都是通过mapper接口进行开发;
注意：此处添加了@Mapper注解，用以Spring把该mapper接口添加到bean容器，否则会报找不到的错误，也可以使用其他bean配置方法
package com.itest.springbootdemo.mapper;
import com.itest.springbootdemo.pojo.Emp;
import org.apache.ibatis.annotations.Mapper;
@Mapper
public interface EmpMapper {
/**
* 根据id查询员工信息
*
* @param id
* @return
*/
public Emp findById(Integer id);
}
3-4 Mapper.xml
注意，namespace需要对应pojo类，id需要对应mapper接口中的方法名
<?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.itest.springbootdemo.mapper.EmpMapper">
<select id="findById" resultType="com.itest.springbootdemo.pojo.Emp">
select * from emp where id = #{id}
</select>
</mapper>
04 编写SpringBoot代码，Service -> impl -> Controller
4-1 Service interface
给Controller提供调用
package com.itest.springbootdemo.service;
import com.itest.springbootdemo.pojo.Emp;
public interface EmpService {
/**
* 根据id查询员工信息
*
* @param id
* @return
*/
public Emp findById(Integer id);
}
4-2 impl
实现上述接口，
注意，实现类中需要增加spring-ioc注解@Service
在此实现类中，调用mybatis mapper接口
package com.itest.springbootdemo.service.impl;
import com.itest.springbootdemo.mapper.EmpMapper;
import com.itest.springbootdemo.pojo.Emp;
import com.itest.springbootdemo.service.EmpService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
@Service
public class EmpServiceImpl implements EmpService {
@Autowired
EmpMapper empMapper;
@Override
public Emp findById(Integer id) {
return empMapper.findById(id);
}
}
4-3 Controller
此段内容为暴露http接口，
注意，controller类添加了注解@RestController，是用于创建RESTful API的注解
在控制器类的方法上添加@GetMapping注解，指定要处理的HTTP GET请求的URL路径。方法可以返回各种类型的数据，如String、JSON、XML等。
package com.itest.springbootdemo.controller;
import com.alibaba.fastjson.JSONObject;
import com.itest.springbootdemo.pojo.Emp;
import com.itest.springbootdemo.service.EmpService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.CrossOrigin;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
@CrossOrigin
@RestController
public class EmpController {
@Autowired
EmpService empService;
@GetMapping("/find")
public String find(Integer id){
Emp result = empService.findById(id);
return JSONObject.toJSONString(result);
}
}
05 运行程序
找到@SpringBootApplication标记的类，点击运行即可
SpringBoot内置了Tomcat容器，所以不需要多余操作，就可以运行程序
测试：运行后，请求地址：http://127.0.0.1:9090/find?id=2 可以正常返回数据
跨域问题解决
SpringBoot提供了解决跨域问题的注解，只要在controller类上添加@CrossOrigin，即可实现跨域，非常方便快捷