Spring Boot入门

什么是Spring Boot？

自行百度

第一个Spring Boot程序

使用IDEA创建Spring Boot项目的步骤：

• New Project，选择左侧的Spring Initializr，注意URL选择默认的https://start.spring.io
  Spring Initializr

• 自定义Group和Artifact，type选择Maven Project

  
  选择TYPE

• 勾选web模块的web

  
  web模块
  修改项目名
  

  注意第一次使用Spring Initializr的话，需要等待时间，因为IDEA需要下载相关依赖包

  
  下载依赖包
• 创建的项目结构如图所示：
  项目结构
• IDEA已经为我们自动添加pom.xml的相关配置
  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>

    <groupId>com.enoch.studio</groupId>
    <artifactId>spring-boot-demo</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>spring-boot-demo</name>
    <description>Demo project for Spring Boot</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.5.9.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.7</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>
    </dependencies>

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

</project>

可以发现IDEA已经为我们创建了一个spring boot的启动类SpringBootDemoApplication.class

package com.enoch.studio;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class SpringBootDemoApplication {

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

其中@SpringBootApplication的作用

这里我们新建一个UserController.class

package com.enoch.studio.controller;

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

/**
 * Created by Enoch on 2017/12/14.
 */
@RestController
public class UserController {
    @RequestMapping(value = "/hello")
    public String hello() {
        return "Hello, Spring Boot!!!";
    }
}

其中@RestController的作用

Spring Boot的启动方式

默认8080端口

第一种：idea 在main函数所在类直接右击选择“run”

第二种：在项目根目录下，cmd运行

mvn spring-boot:run

第三种：在项目根目录下，cmd运行

mvn install

然后在target目录下可以发现产生了一个spring-boot-demo-0.0.1-SNAPSHOT.jar文件 cmd运行

java -jar spring-boot-demo-0.0.1-SNAPSHOT.jar

运行后，就可以访问地址：

localhost:8080/hello

spring boot的配置文件

application.properties

application.yml

推荐使用后者

application.properties配置示例

#配置端口
server.port=8088
#配置根路径
server.context-path=/springboot

配置之后重新运行，访问地址：

localhost:8088/springboot/hello

得到相同的效果

application.yml配置示例

server:
  port: 8088
  context-path: /springboot

这里要注意：冒号后面要添加一个空格

自定义属性

server:
  #配置端口
  port: 8088
  #配置路径
  context-path: /springboot

#自定义变量
studioName: ENOCH STUDIO

使用自定义变量，使用@Value的${}
示例：

package com.enoch.studio.controller;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

/**
 * Created by Enoch on 2017/12/14.
 */
@RestController
public class UserController {
    @Value("${studioName}")
    private String studioName;

    @RequestMapping(value = "/hello")
    public String hello() {
        return "Hello, Spring Boot!!! " + studioName;
    }
}

配置多个属性示例
application.yml

user:
  username: Enoch
  age: 22

新建一个User类

package com.enoch.studio.entity;

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

/**
 * Created by Enoch on 2017/12/14.
 */
@Component
@ConfigurationProperties(prefix = "user")
public class User {
    private String username;
    private Integer age;

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public Integer getAge() {
        return age;
    }

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

    @Override
    public String toString() {
        return "User{" +
                "username='" + username + '\'' +
                ", age=" + age +
                '}';
    }
}

注意@Component作用是自动扫描
@ConfigurationProperties作用是配置属性

修改UserController.java

package com.enoch.studio.controller;

import com.enoch.studio.entity.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

/**
 * Created by Enoch on 2017/12/14.
 */
@RestController
public class UserController {
    @Autowired
    private User user;
    @Value("${studioName}")
    private String studioName;

    @RequestMapping(value = "/hello")
    public String hello() {
        return "Hello, Spring Boot!!! " + user;
    }
}

多环境配置，比如开发环境、测试环境以及生产环境
新建多个yml
分别命名为

application.yml
application-dev.yml
application-test.yml
application-prod.yml

application.yml配置示例：

spring:
  profiles:
    active: dev

即可通过修改active的属性值选择对应的环境

数据库操作

spring-data-jpa

1.yml配置

spring:
  profiles:
    active: dev
  datasource:
    driver-class-name: com.mysql.jdbc.Driver
    url: jdbc:mysql://localhost:3306/idea_dev
    username: root
    password: whuwjw2013
  jpa:
    database-platform: org.hibernate.dialect.MySQL5Dialect
    hibernate:
      ddl-auto: create
    show-sql: true

pom.xml配置
添加两个依赖：jpa和mysql

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

2.编写entity类

package com.enoch.studio.entity;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;

/**
 * Created by Enoch on 2017/12/14.
 */
@Entity
public class Role {
    @Id
    @GeneratedValue
    private Integer id;
    private String roleName;

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getRoleName() {
        return roleName;
    }

    public void setRoleName(String roleName) {
        this.roleName = roleName;
    }
}

注意@Entity和@Id以及@GeneratedValue的作用

3.编写repository接口并继承JpaRepository接口

package com.enoch.studio.repository;

import com.enoch.studio.entity.Role;
import org.springframework.data.jpa.repository.JpaRepository;

/**
 * Created by Enoch on 2017/12/14.
 */
public interface RoleRepository extends JpaRepository<Role,Integer> {
}

4.在controller层调用，这里由于逻辑简单，所以直接在controller层调用，原则上是在service层调用

package com.enoch.studio.controller;

import com.enoch.studio.entity.Role;
import com.enoch.studio.repository.RoleRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.List;

/**
 * Created by Enoch on 2017/12/14.
 */
@RestController
@RequestMapping("/role")
public class RoleController {
    @Autowired
    private RoleRepository roleRepository;
    @GetMapping(value = "/roleList")
    public List<Role>  roleList() {
        return roleRepository.findAll();
    }
}