1.创建项目

New Project，选择Spring Initializr

输入基本信息

选择web，然后一路next下去，中间有设置项目路径的，想改就改

然后把结构稍微调整下，改一改

配置端口号，在application.yml里

#配置端口号
server:
  port: 8080

然后在controller层里建个HelloController，加点代码测试下

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IDEA直接run，或者右击启动类run（项目创建时候里面代码默认就有了，直接跑）

成功

2.简单使用

@Value注解可以直接从配置文件里获取值

@Value("${name}")
private String name;

@Value("${age}")
private Integer age;

@Value("${content}")
private String content;

@RequestMapping(value = "/", method = RequestMethod.GET)
public String say() {
    return content;
}

下面是直接输出content的

2.实体类获取配置文件值

创建Student实体类

@Component
@ConfigurationProperties(prefix = "student")
public class Student {

    private Integer id;

    private String name;

    private Integer age;

    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 Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }
}

在pom.xml文件配置加上，这个是防止实体类里报错的

<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-configuration-processor</artifactId>
  <optional>true</optional>
</dependency>

没加的话会这样

@Component 用于把对象注册成bean

@ConfigurationProperties(prefix = "student") 用于获取配置文件里对象叫student的值

3. @RequestMapping 和 @PathVariable 的作用，在URL地址栏中输入id，然后自己获取此id并且在浏览器上打印出来。

@RequestMapping(value = "/num/{id}", method = RequestMethod.GET)
public String num(@PathVariable("id") Integer id) {
    return "id = " + id;
}

运行

4.通过 ? 来获取URL值，配合 @RequestParam 注解使用

@RequestMapping 可以用 @GetMapping 和 @PostMapping来代替

@GetMapping(value = "/num2")
public String num2(@RequestParam(value = "id", defaultValue = "0", required = false) Integer id) {
    return "id = " + id;
}

3.连接数据库

application.yml中加入配置

#配置数据库
spring:
  profiles:
    active: a
  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://127.0.0.1:3306/test?useUnicode=true&characterEncoding=utf8&serverTimezone=GMT
    username: root
    password: root

#配置xml映射
mybatis:
  mapper-locations: mapper/*.xml

sql

DROP TABLE IF EXISTS `student`;
CREATE TABLE `student` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(50) COLLATE utf8_unicode_ci DEFAULT NULL,
  `age` int(11) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=MyISAM AUTO_INCREMENT=3 DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;


INSERT INTO `student` VALUES ('1', 'Lin', '24');
INSERT INTO `student` VALUES ('2', 'you', '23');

pom文件引入SQL的包

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>

<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
</dependency>

启动器加入注解扫描

@ComponentScan 用于扫描 Controller层，service层

@MapperScan 用于扫描mapper层

在使用 @MapperScan 之前需要在pom引入

<!-- 分页插件 -->
<dependency>
    <groupId>com.github.pagehelper</groupId>
    <artifactId>pagehelper-spring-boot-starter</artifactId>
    <version>1.2.5</version>
</dependency>

controller层：

 @GetMapping(value = "/getStudent")
 public List<Student> getStudent() {
     return helloService.getStudent();
 }

xml：

<?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.springboot.test.mapper.HelloRepository">

    <select id="getStudent" resultType="com.springboot.test.entity.Student">
        select * from student
    </select>

</mapper>

运行：

下面是所有文件代码：

Student.java：

package com.springboot.test.entity;

import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.stereotype.Component;

@Component
@ConfigurationProperties(prefix = "student")
public class Student {

    private Integer id;

    private String name;

    private Integer age;

    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 Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }
}

HelloController.java：

package com.springboot.test.controller;

import com.springboot.test.entity.Student;
import com.springboot.test.service.HelloService;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.web.bind.annotation.*;

import javax.annotation.Resource;
import java.util.List;

@RestController
public class HelloController {

    @Resource
    private Student student;

    @Resource
    private HelloService helloService;

    @Value("${name}")
    private String name;

    @Value("${age}")
    private Integer age;

    @Value("${content}")
    private String content;

    @RequestMapping(value = "/", method = RequestMethod.GET)
    public String say() {
        return content;
    }

    @RequestMapping(value = "/student", method = RequestMethod.GET)
    public String stu() {
        return student.getName();
    }

    @RequestMapping(value = "/num/{id}", method = RequestMethod.GET)
    public String num(@PathVariable("id") Integer id) {
        return "id = " + id;
    }

    @GetMapping(value = "/num2")
    public String num2(@RequestParam(value = "id", defaultValue = "0", required = false) Integer id) {
        return "id = " + id;
    }

    @GetMapping(value = "/getStudent")
    public List<Student> getStudent() {
        return helloService.getStudent();
    }
}

HelloService.java：

package com.springboot.test.service;

import com.springboot.test.entity.Student;

import java.util.List;

public interface HelloService {

    List<Student> getStudent();
}

HelloServiceImpl.java：

package com.springboot.test.service.impl;

import com.springboot.test.mapper.HelloRepository;
import com.springboot.test.entity.Student;
import com.springboot.test.service.HelloService;
import org.springframework.stereotype.Service;

import javax.annotation.Resource;
import java.util.List;

@Service("HelloService")
public class HelloServiceImpl implements HelloService {

    @Resource
    private HelloRepository helloRepository;

    @Override
    public List<Student> getStudent() {
        return helloRepository.getStudent();
    }
}

HelloMapper.java：

package com.springboot.test.mapper;

import com.springboot.test.entity.Student;

import java.util.List;


public interface HelloMapper {

    List<Student> getStudent();
}

HelloMapper.xml：

<?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.springboot.test.mapper.HelloMapper">

    <select id="getStudent" resultType="com.springboot.test.entity.Student">
        select * from student
    </select>

</mapper>

Application.java：

package com.springboot.test;

import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.ComponentScan;

@ComponentScan(basePackages = {"com.springboot.test.*"})
@MapperScan("com.springboot.test.mapper")
@SpringBootApplication
public class Application {

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }

}

application.yml：

#配置端口号
server:
  port: 8080

#配置数据库
spring:
  profiles:
    active: a
  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://127.0.0.1:3306/test?useUnicode=true&characterEncoding=utf8&serverTimezone=GMT
    username: root
    password: root

#配置xml映射
mybatis:
  mapper-locations: mapper/*.xml


name: Jack
age: 18
content: "name: ${name}, age: ${age}"

student:
  name: Michael
  age: 20

pom.xml：

<?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 http://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>2.1.1.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.springboot</groupId>
    <artifactId>test</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>test</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-configuration-processor</artifactId>
            <optional>true</optional>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
        </dependency>

        <!-- 分页插件 -->
        <dependency>
            <groupId>com.github.pagehelper</groupId>
            <artifactId>pagehelper-spring-boot-starter</artifactId>
            <version>1.2.5</version>
        </dependency>

    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

IDEA搭建SpringBoot项目，以及简单使用

1.创建项目

2.简单使用

3.连接数据库

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