2.Springboot 之 Helloworld

左手的ㄟ右手 2022-06-17 05:11 145阅读 0赞

# 本文所属【[知识林][Link 1]】：http://www.zslin.com/web/article/detail/7    #

上一篇说了Springboot的那么多好处，说得有多么的高效，现在先构造一个Helloworld来看一下具体的效果。

在Springboot的开发中本人比较喜欢使用IDEA开发工具（构建比较方便），[点击这里可进入IDEA的下载页面][IDEA]

### 第一步、构造项目 ###

*  点击File -> New -> Project
 *  左边选择`Maven`，右边什么都不用选择，点击`Next`或按`Alt+N`
 *  在GroupId处输入包名，如：`com.zslin`（一般用域名反写）
 *  在ArtifactId处输入工程ID，如：`study01`（用于项目中显示的名称），点击`Next`或按`Alt+N`
 *  在Project name处输入项目名称，如：`study01`（用于磁盘中存储的文件夹名）
 *  在Project location处输入或选择项目存放在磁盘的路径，点击`Finish`或按`Alt+F`

完成项目构建。

### 第二步、配置pom.xml ###

项目构建完成后在pom.xml（Maven配置文件）文件中引入Springboot的配置。

1、 引入spring-boot-starter-parent，这里使用版本为1.4.0.RELEASE

<parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.4.0.RELEASE</version>
        <relativePath/> 
    </parent>

2、 引入最基础的依赖  
由于继承了starter-parent，且指定了相应版本，所以在引入Springboot相关的依赖时不再需要指定版本，Springboot会自动寻找最合适的版本。

<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>

完成的pom.xml文件如下：

<?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.zslin</groupId>
        <artifactId>study01</artifactId>
        <version>1.0-SNAPSHOT</version>
    
        <parent>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-parent</artifactId>
            <version>1.4.0.RELEASE</version>
            <relativePath/>
        </parent>
    
        <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>
    
    </project>

### 第三步、创建测试类 ###

package com.zslin.controller;
    
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RestController;
    
    /**
     * Created by zslin.com on 2016/10/13.
     */
    @RestController
    public class IndexController {
    
        @RequestMapping(value = "index")
        public String index() {
    
            return "Hello World!!!";
        }
    }

注意：
    
    1、这一步可以不要，但为了更友好的显示效果，所以还是写了。
    2、该java文件所在的包是由第一步中的GroupId处输入的包名而定的。

### 第四步、创建启动文件 ###

新建一个Java对象命名为`RootApplication.java`（名称可自己定义）。  
全代码如下：

package com.zslin;
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    
    /**
     * Created by zslin.com on 2016/10/13.
     */
    @SpringBootApplication
    public class RootApplication {
    
        public static void main(String [] args) {
            SpringApplication.run(RootApplication.class, args);
        }
    }

注意：
    
    1、`RootApplication.java`需要在`com.zslin`包里，这个包是由第一步中的GroupId处输入的包名而写；
    2、`RootApplication.java`在类名上加注释`@SpringBootApplication`；
    3、在该类里的main方法上启动运行。

### 第五步、运行main方法 ###

.   ____          _            __ _ _
     /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
    ( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
     \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
      '  |____| .__|_| |_|_| |_\__, | / / / /
     =========|_|==============|___/=/_/_/_/
     :: Spring Boot ::        (v1.4.0.RELEASE)
    
    2016-10-13 00:52:04.534  INFO 6828 --- [           main] com.zslin.RootApplication                : Starting RootApplication on zsl with PID 6828 (E:\idea\2016_zslin\study01\target\classes started by zsl-pc in E:\idea\2016_zslin\study01)
    2016-10-13 00:52:04.538  INFO 6828 --- [           main] com.zslin.RootApplication                : No active profile set, falling back to default profiles: default
    2016-10-13 00:52:04.666  INFO 6828 --- [           main] ationConfigEmbeddedWebApplicationContext : Refreshing org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext@9225652: startup date [Thu Oct 13 00:52:04 CST 2016]; root of context hierarchy
    2016-10-13 00:52:07.340  INFO 6828 --- [           main] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat initialized with port(s): 8080 (http)
    2016-10-13 00:52:07.352  INFO 6828 --- [           main] o.apache.catalina.core.StandardService   : Starting service Tomcat
    2016-10-13 00:52:07.353  INFO 6828 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet Engine: Apache Tomcat/8.5.4
    2016-10-13 00:52:07.473  INFO 6828 --- [ost-startStop-1] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
    2016-10-13 00:52:07.474  INFO 6828 --- [ost-startStop-1] o.s.web.context.ContextLoader            : Root WebApplicationContext: initialization completed in 2815 ms
    2016-10-13 00:52:07.664  INFO 6828 --- [ost-startStop-1] o.s.b.w.servlet.ServletRegistrationBean  : Mapping servlet: 'dispatcherServlet' to [/]
    2016-10-13 00:52:07.670  INFO 6828 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'characterEncodingFilter' to: [/*]
    2016-10-13 00:52:07.671  INFO 6828 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'hiddenHttpMethodFilter' to: [/*]
    2016-10-13 00:52:07.671  INFO 6828 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'httpPutFormContentFilter' to: [/*]
    2016-10-13 00:52:07.671  INFO 6828 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'requestContextFilter' to: [/*]
    2016-10-13 00:52:07.997  INFO 6828 --- [           main] s.w.s.m.m.a.RequestMappingHandlerAdapter : Looking for @ControllerAdvice: org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext@9225652: startup date [Thu Oct 13 00:52:04 CST 2016]; root of context hierarchy
    2016-10-13 00:52:08.065  INFO 6828 --- [           main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/index]}" onto public java.lang.String com.zslin.controller.IndexController.index()
    2016-10-13 00:52:08.070  INFO 6828 --- [           main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/error]}" onto public org.springframework.http.ResponseEntity<java.util.Map<java.lang.String, java.lang.Object>> org.springframework.boot.autoconfigure.web.BasicErrorController.error(javax.servlet.http.HttpServletRequest)
    2016-10-13 00:52:08.071  INFO 6828 --- [           main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/error],produces=[text/html]}" onto public org.springframework.web.servlet.ModelAndView org.springframework.boot.autoconfigure.web.BasicErrorController.errorHtml(javax.servlet.http.HttpServletRequest,javax.servlet.http.HttpServletResponse)
    2016-10-13 00:52:08.105  INFO 6828 --- [           main] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/webjars/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
    2016-10-13 00:52:08.105  INFO 6828 --- [           main] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
    2016-10-13 00:52:08.148  INFO 6828 --- [           main] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/**/favicon.ico] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
    2016-10-13 00:52:08.294  INFO 6828 --- [           main] o.s.j.e.a.AnnotationMBeanExporter        : Registering beans for JMX exposure on startup
    2016-10-13 00:52:08.359  INFO 6828 --- [           main] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat started on port(s): 8080 (http)
    2016-10-13 00:52:08.363  INFO 6828 --- [           main] com.zslin.RootApplication                : Started RootApplication in 4.436 seconds (JVM running for 4.958)

可以看到程序已成功运行，且默认端口是`8080`，此时可以在浏览器里输入地址查看效果：  
`http://localhost:8080/index`，网页上显示：`Hello World!!!`就表示网站已成功搭建完成！

[Link 1]: http://www.zslin.com/
[IDEA]: https://www.jetbrains.com/idea/download