SpringBoot入门_HelloWorld

作者: SpaceCat | 来源:发表于2019-03-25 12:12 被阅读0次

Spring Boot是由Pivotal团队提供的全新框架,其设计目的是用来简化新Spring应用的初始搭建以及开发过程。该框架使用了特定的方式来进行配置,从而使开发人员不再需要定义样板化的配置。通过这种方式,Spring Boot致力于在蓬勃发展的快速应用开发领域(rapid application development)成为领导者。(From 百度百科)

1、新建第一个SpringBoot Web工程

在IDEA中,新建工程时选择Spring Initializr

Spring Initializr
修改Group名和Artifact名称:
修改Group名和Artifact名称
依赖选择Web:
依赖选择Web
输入工程名称:
输入工程名称
创建完成后的工程目录结构如下:
工程目录结构

Spring Boot的基础结构共三个文件(具体路径根据用户生成项目时填写的Group和Artifact所有差异):

  • src/main/java下的程序入口:com.lfqy.HelloworldApplication.java
  • src/main/resources下的配置文件:application.properties,当前该文件内容为空。
  • src/test/下的测试入口:com.lfqy.HelloworldApplication.java

2、实现第一个helloworld

这里大概分几步:新建url的响应逻辑;设置basePackage;更新maven。

2.1 新建url的响应逻辑

src/main/java目录下,新建一个包com.hello.world.controller
然后,在该包中新建一个类HelloWorldController.java,代码如下:

package com.hello.world.controller;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * Created by chengxia on 2019/3/25.
 */
@RestController
@EnableAutoConfiguration
public class HelloWorldController {
    @RequestMapping
    public String index() {
        return "Hello World";
    }
    @RequestMapping("/helloworld")
    public String helloworld() {
        return "Hello World";
    }
    @RequestMapping("test/hello")
    public String testHelloworld() {
        return "Hello World";
    }
    @RequestMapping("/info")
    public Map<String,String> getInfo(@RequestParam String name){
        Map<String,String> map = new HashMap<>();
        map.put ("name",name);
        return map;
    }
    @RequestMapping("/list")
    public List<Map<String,String>> getList(){
        List<Map<String,String>> list = new ArrayList<>();
        Map<String,String> map = null;
        for (int i=1;i<=5;i++){
            map = new HashMap<> ();
            map.put ("name","gogogo"+i);
            list.add (map);
        }
        return list;
    }
}

2.2 设置basePackage

这是很关键的一步,不然工程可以启动,但是访问url会报404。打开工程中的HelloworldApplication.java文件,在其中给这个类加一个注解@ComponentScan(basePackages = "com.hello.world.controller")。修改后的HelloworldApplication.java文件如下:

package com.lfqy;

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

@SpringBootApplication
@ComponentScan(basePackages = "com.hello.world.controller")
public class HelloworldApplication {

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

}

2.3 更新maven

这一步对于新手来说,比较容易忽略,现象就是上面做完之后,打开HelloworldApplication.java,找不到运行的按钮。
在IDEA中,点开MAVEN标签,点击刷新按钮,如下图:


执行maven刷新

更新之后,会发现源文件的图标都变了(如上图)。

3、运行

打开HelloworldApplication.java,在该源码文件中,右键鼠标,可以看到名为Run'HelloworldAppl....main()'的运行按钮,点击就启动了工程。控制台输出如下:

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v2.1.3.RELEASE)

2019-03-25 09:58:15.951  INFO 694 --- [           main] com.lfqy.HelloworldApplication           : Starting HelloworldApplication on ChengdeMacBook-Pro.local with PID 694 (/Users/chengxia/Developer/Java/springboothelloworld/target/classes started by chengxia in /Users/chengxia/Developer/Java/springboothelloworld)
2019-03-25 09:58:15.955  INFO 694 --- [           main] com.lfqy.HelloworldApplication           : No active profile set, falling back to default profiles: default
2019-03-25 09:58:17.381  INFO 694 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with port(s): 8080 (http)
2019-03-25 09:58:17.425  INFO 694 --- [           main] o.apache.catalina.core.StandardService   : Starting service [Tomcat]
2019-03-25 09:58:17.426  INFO 694 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet engine: [Apache Tomcat/9.0.16]
2019-03-25 09:58:17.440  INFO 694 --- [           main] o.a.catalina.core.AprLifecycleListener   : The APR based Apache Tomcat Native library which allows optimal performance in production environments was not found on the java.library.path: [/Users/chengxia/Library/Java/Extensions:/Library/Java/Extensions:/Network/Library/Java/Extensions:/System/Library/Java/Extensions:/usr/lib/java:.]
2019-03-25 09:58:17.593  INFO 694 --- [           main] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2019-03-25 09:58:17.594  INFO 694 --- [           main] o.s.web.context.ContextLoader            : Root WebApplicationContext: initialization completed in 1531 ms
2019-03-25 09:58:17.948  INFO 694 --- [           main] o.s.s.concurrent.ThreadPoolTaskExecutor  : Initializing ExecutorService 'applicationTaskExecutor'
2019-03-25 09:58:18.282  INFO 694 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8080 (http) with context path ''
2019-03-25 09:58:18.287  INFO 694 --- [           main] com.lfqy.HelloworldApplication           : Started HelloworldApplication in 18.044 seconds (JVM running for 18.886)

在浏览器中访问如下地址:
http://127.0.0.1:8080/
http://127.0.0.1:8080/helloworld
http://127.0.0.1:8080/test/hello
http://127.0.0.1:8080/list
http://127.0.0.1:8080/info?name=Paopao
就可得到我们前面代码中的逻辑响应。下图是一个例子:

run result

参考资料

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