IDEA入门SpringBoot看这一篇就够了，手把手创建工程、开发接口、自定义配置、三层架构实现数据访问
idea快速入门SpringBoot
仓库地址：https://gitee.com/baby-gitee/spring-boot-learn.git
1.创建工程
1.1 Spring Initializr
选择SDK：(8)
选择Default
Next
1.2 Project Metadata
Group：输入域名反写（com.XXX）
Artifact：输入项目名（spring-boot-learn）
Type：选择(Maven)
Language：选择语言(Java)
Java Version：选择java版本(8)
Descriptio：描述
Next
1.3 Dependencies
Spring Boot：选择版本（2.2.2）
搜索依赖：输入依赖名（web）
选择（Spring Web）
…
Next
1.4 选择文件要放置的位置…点击完成
项目结构
入口：SpringBootLearnApplication
配置文件：src/main/java/…/springbootlearn/SpringBootLearnApplication.java
测试入口：src/test/java/com/baby/springbootlearn/SpringBootLearnApplicationTests.java
1.5 修改Pom.xml
version改为想要的springboot版本(2.2.1.RELEASE)
1.5.1 右键Pom.xml文件>Maven>Reimport
idea可能存在bug，刷新后2.2.1.RELEASE报红
如果可以成功运行，则无需理会
解读Pom.xml
spring-boot版本
org.springframework.boot spring-boot-starter-parent 2.2.1.RELEASE 项目名称
com.baby spring-boot-learn 0.0.1-SNAPSHOT spring-boot-learn Demo project for Spring Boot java版本
1.8 依赖
org.springframework.boot spring-boot-starter-web org.springframework.boot spring-boot-starter-test test 插件
Maven项目对于SpringBoot是需要这个插件的org.springframework.boot spring-boot-maven-plugin
运行项目
浏览器访问http://localhost:8080/页面提示Whitelabel Error Page说明启动成功
2.开发接口
在com.XXX.springbootlearn下创建包controller
在controller包下创建ParaController
创建的Controller必须放在…Application.java同目录下或同目录的子包下
否则会找不到
2.1 编写第一个接口
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
/**
* @Author: BaBy
* @Date: 2021/3/7 21:01
*/
@RestController
public class ParaController {
@GetMapping("/firstrequest")
public String firstRequest(){
return "firstRequest";
}
}
运行项目
浏览器中输入localhost:8080/firstrequest访问
页面显示：firstRequest
2.2 编写获取参数的接口
public class ParaController {
...
@GetMapping("/requestpara")
public String requestpara(@RequestParam Integer num){
return "para from request: "+num;
}
}
运行项目
浏览器中输入localhost:8080/requestpara访问
页面显示：Whitelabel Error Page。。。
浏览器中输入localhost:8080/requestpara?num=5访问
页面显示：para from request: 5
2.3 编写获取路径参数的接口
public class ParaController {
...
@GetMapping("/pathpara/{num}")
public String pathpara(@PathVariable Integer num){
return "para from path: "+num;
}
}
运行项目
浏览器中输入localhost:8080/pathpara/5访问
页面显示：para from path: 5
2.4 统一前缀接口
@RestController
@RequestMapping("pre")
public class ParaController {
...
@GetMapping("/pathpara/{num}")
public String pathpara(@PathVariable Integer num){
return "para from path: "+num;
}
}
运行项目
浏览器中输入localhost:8080/pre/pathpara/5访问
页面显示：para from path: 5
2.5 多url的用法
@RestController
@RequestMapping("pre")
public class ParaController {
...
@GetMapping({"/multiurl1","/multiurl2"})
public String multiurl(@RequestParam Integer num){
return "multiurl: "+num;
}
}
运行项目
浏览器中输入localhost:8080/pre/multiurl1?num=5访问
页面显示：multiurl: 5
浏览器中输入localhost:8080/pre/multiurl2?num=5访问
页面显示：multiurl: 5
2.6 传参默认值
@RestController
@RequestMapping("pre")
public class ParaController {
...
@GetMapping("/required")
public String required(@RequestParam(required = false, defaultValue = "0") Integer num){
return "para from required: "+num;
}
}
运行项目
浏览器中输入localhost:8080/pre/required访问
页面显示：para from required: 0
浏览器中输入localhost:8080/pre/multiurl2?num=5访问
页面显示：para from required: 5
3.自定义配置
3.1配置文件
3.1.1 在controller包下创建PropertiesController
package com.baby.springbootlearn.controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
/**
* @Author: BaBy
* @Date: 2021/3/7 22:06
*/
@RestController
public class PropertiesController {
Integer key1;
Integer key2;
@GetMapping("/getValue")
public String getValue(){
return "key1="+key1+",key2="+key2;
}
}
3.1.2 在application.properties中
key.key1=3
key.key2=4
运行项目
访问http://localhost:8080/getValue
页面显示：key1=null,key2=null
3.1.3 修改PropertiesController
@RestController
public class PropertiesController {
@Value("${key.key1}")
Integer key1;
@Value("${key.key2}")
Integer key2;
...
}
按住ctrl点击${key1}会跳转到application配置文件，说明绑定成功
运行项目
访问http://localhost:8080/getValue
页面显示：key1=3,key2=4
3.2 配置类
3.2.1 创建config包，在config创建keyConfig配置类
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.stereotype.Component;
/**
* @Author: BaBy
* @Date: 2021/3/7 22:33
*/
@Component
@ConfigurationProperties(prefix = "key")
public class KeyConfig {
private Integer key1;
private Integer key2;
public Integer getKey1() {
return key1;
}
public void setKey1(Integer key1) {
this.key1 = key1;
}
public Integer getKey2() {
return key2;
}
public void setKey2(Integer key2) {
this.key2 = key2;
}
}
必须加上getter和setter
否值无效
3.2.2 在controller创建ConfigController控制器
import com.baby.springbootlearn.config.KeyConfig;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
/**
* @Author: BaBy
* @Date: 2021/3/7 22:38
*/
@RestController
public class ConfigController {
@Autowired
KeyConfig keyConfig;
@GetMapping("/getValuefromconfig")
public String getValue(){
return "key1="+keyConfig.getKey1()+",key2="+keyConfig.getKey2();
}
}
运行项目
访问http://localhost:8080/getValuefromconfig
页面显示：key1=3,key2=4
4.完成三层架构
4.1 在mysql中创建数据库student， 执行以下SQL
SET NAMES utf8mb4;
SET FOREIGN_KEY_CHECKS = 0;
-- ----------------------------
-- Table structure for student
-- ----------------------------
DROP TABLE IF EXISTS `student`;
CREATE TABLE `student` (
`id` int NOT NULL AUTO_INCREMENT,
`name` varchar(255) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci;
-- ----------------------------
-- Records of student
-- ----------------------------
BEGIN;
INSERT INTO `student` VALUES (1, '小明');
INSERT INTO `student` VALUES (2, '小美');
COMMIT;
SET FOREIGN_KEY_CHECKS = 1;
4.2 在pom.xml中引入依赖：mybatis、mysql驱动
...
org.mybatis.spring.boot
mybatis-spring-boot-starter
2.1.1
mysql
mysql-connector-java
4.3 在application.properties中写配置
mysql5.x 使用的驱动是com.mysql.jdbc.Driver
mysql8.x 使用的驱动是com.mysql.cj.jdbc.Driver
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
spring.datasource.username=root
spring.datasource.password=root
spring.datasource.url=jdbc:mysql://localhost:3306/springbootlearn?useSSL=false&useUnicode=true&characterEncoding=UTF-8&allowPublicKeyRetrieval=true&serverTimezone=Asia/Shanghai
4.4 在entity包下创建Student实体
public class Student {
private Long id;
private String name;
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@Override
public String toString() {
return "Student{" +
"id=" + id +
", name='" + name + '\'' +
'}';
}
}
4.5 在dao包下创建StudentMapper
import com.baby.springbootlearn.entity.Student;
import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Select;
import org.springframework.stereotype.Repository;
/**
* @Author: BaBy
* @Date: 2021/3/7 23:18
*/
@Mapper
@Repository
public interface StudentMapper {
@Select("select id,name from student where id = #{id}")
Student findById(Integer id);
}
4.6 在service包下创建StudentService服务接口
import com.baby.springbootlearn.entity.Student;
/**
* @Author: BaBy
* @Date: 2021/3/7 23:16
*/
public interface StudentService {
public Student findStudentById(Integer id);
}
4.7 在service.impl包下创建StudentServiceImpl服务接口
import com.baby.springbootlearn.dao.StudentMapper;
import com.baby.springbootlearn.entity.Student;
import com.baby.springbootlearn.service.StudentService;
import org.springframework.stereotype.Service;
import javax.annotation.Resource;
/**
* @Author: BaBy
* @Date: 2021/3/7 23:27
*/
@Service("studentService")
public class StudentServiceImpl implements StudentService {
@Resource
private StudentMapper studentMapper;
@Override
public Student findStudentById(Integer id) {
return studentMapper.findById(id);
}
}
4.8 在controller包下创建StudentController控制器
import com.baby.springbootlearn.entity.Student;
import com.baby.springbootlearn.service.StudentService;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;
import javax.annotation.Resource;
import javax.validation.constraints.NotNull;
/**
* @Author: BaBy
* @Date: 2021/3/7 23:12
*/
@RestController
public class StudentController {
@Resource
private StudentService studentService;
@GetMapping("/student/{id}")
public String student(@NotNull @PathVariable Integer id){
Student student = studentService.findStudentById(id);
return student.toString();
}
}
运行项目
访问http://localhost:8080/student/1
页面显示：Student{id=1, name=‘小明’}