一起学JAVA之《spring boot》02-开发您的第一个S

作者: IT_JAVA_文艺男 | 来源:发表于2017-06-25 20:19 被阅读0次

一、导航

本节内容简介：
1. 开发之前环境检查
2. 创建pom.xml并导入依赖
3. 编写代码
4. 代码解释
5. 运行代码
6. 创建可执行的jar

二、开发之前环境检查

让我们在Java中开发一个简单的 Hello World 的Web应用程序，来介绍Spring Boot一些主要的功能。
这里将使用Maven构建该项目。

在开始之前，打开终端（windwos cmd）来验证java版本和maven版本

C:\Users\SEELE>java -version
java version "1.8.0_121"
Java(TM) SE Runtime Environment (build 1.8.0_121-b13)
Java HotSpot(TM) 64-Bit Server VM (build 25.121-b13, mixed mode)

这里要注意检查maven版本不是maven -v,而是mvn -v

C:\Users\SEELE>mvn -v
Apache Maven 3.2.5 (12a6b3acb947671f09b81f49094c53f426d8cea1...

三、创建pom.xml并导入依赖

使用idea创建一个maven项目，并添加maven 父类依赖

<?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.likeoak</groupId>
    <artifactId>springboot</artifactId>
    <version>1.0.0</version>

    <!--添加父类依赖-->
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.5.2.RELEASE</version>
    </parent>

</project>

添加web依赖


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

四、编写代码

默认情况下，Maven将从src/main/java编译源代码，因此您需要创建该文件夹结构，然后添加一个名为src/main/java/Example.java的文件：
注意：官方建议不要使用默认的default包来创建启动类，这样会导致所有的包都会被扫描，包括jar


package com.likeoak;


import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

/**
 * The type Spring boot example.
 */
RestController
EnableAutoConfiguration
public class SpringBootExample {

    @RequestMapping("/")
    String home() {
        return "Hello World!";
    }
    public static void main(String[] args) throws Exception {
        SpringApplication.run(SpringBootExample.class, args);
    }


}

五、代码解释

尽管以上代码不多，但是却发生很多事情，让我们一步一步来解释吧

1. 注解解释
上面一共用了三个注解 @RestController ,@RequestMapping, @EnableAutoConfiguration

@RestController是一个被称为构造性（stereotype）的注解，它表示的意思是是一个REST风格的Controller
@RequestMapping 这个注解是提供路由信息，所有HTTP的 "/"这个请求都会被这个home方法捕获，这个和@RestController一起的意思是，当访问"/"这个路径的时候，就以字符串的形式返回"Hello World!"

@EnableAutoConfiguration 这个注解的意思是告诉spring boot 根据你配置的jar来猜测你想如何配置spring
这里我们配置了spring-boot-starter-web这个jar,spring boot 就会为我们自动配置tomcat和SprngMVC的相关配置
,可以参考下面spring-boot-starter-web依赖包,看到里面有springMVC和tomcat的引用

附spring-boot-starter-web依赖包

<?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-starters</artifactId>
        <version>1.5.2.RELEASE</version>
    </parent>
    <artifactId>spring-boot-starter-web</artifactId>
    <name>Spring Boot Web Starter</name>
    <description>Starter for building web, including RESTful, applications using Spring
        MVC. Uses Tomcat as the default embedded container</description>
    <url>http://projects.spring.io/spring-boot/</url>
    <organization>
        <name>Pivotal Software, Inc.</name>
        <url>http://www.spring.io</url>
    </organization>
    <properties>
        <main.basedir>${basedir}/../..</main.basedir>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-tomcat</artifactId>
        </dependency>
        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-validator</artifactId>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-webmvc</artifactId>
        </dependency>
    </dependencies>
</project>

附spring-boot-starter-tomcat依赖

<?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-starters</artifactId>
        <version>1.5.2.RELEASE</version>
    </parent>
    <artifactId>spring-boot-starter-tomcat</artifactId>
    <name>Spring Boot Tomcat Starter</name>
    <description>Starter for using Tomcat as the embedded servlet container. Default
        servlet container starter used by spring-boot-starter-web</description>
    <url>http://projects.spring.io/spring-boot/</url>
    <organization>
        <name>Pivotal Software, Inc.</name>
        <url>http://www.spring.io</url>
    </organization>
    <properties>
        <main.basedir>${basedir}/../..</main.basedir>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.apache.tomcat.embed</groupId>
            <artifactId>tomcat-embed-core</artifactId>
        </dependency>
        <dependency>
            <groupId>org.apache.tomcat.embed</groupId>
            <artifactId>tomcat-embed-el</artifactId>
        </dependency>
        <dependency>
            <groupId>org.apache.tomcat.embed</groupId>
            <artifactId>tomcat-embed-websocket</artifactId>
        </dependency>
    </dependencies>
</project>

2. main方法
main方法是一个java标准入口方法。这里main方法通过调用runm,将业务委托给了 Spring Boot的 SpringApplication 类。SpringApplication将引导我们启动spring,相应的启动被自动配置的tomcat web服务器，这里我们需要将主类 SpringBootExample作为参数传给run方法，告诉spring boot 那个是主类，并传递args参数给 spring boot,对于这个args参数，我们后续会讲解.

六、运行代码

直接运行main方法

运行结果：

                     .__  .__ __                       __
__  _  ____  _  ____  _  __  |  | |__|  | __ ____  _________  |  | __     ____  ____   _____
\ \/ \/ /\ \/ \/ /\ \/ \/ /  |  | |  |  |/ // __ \/  _ \__  \ |  |/ /   _/ ___\/  _ \ /     \
 \     /  \     /  \     /   |  |_|  |    <\  ___(  <_> ) __ \|    <    \  \__(  <_> )  Y Y  \
  \/\_/    \/\_/    \/\_/ /\ |____/__|__|_ \\___  >____(____  /__|_ \ /\ \___  >____/|__|_|  /
                          \/              \/    \/          \/     \/ \/     \/            \/
2017-06-25 18:58:59.061  INFO 10640 --- [           main] com.likeoak.SpringBootExample            : Starting SpringBootExample on SEELE-PC with PID 10640 (G:\Mybook\springBoot\target\classes started by SEELE in G:\Mybook\springBoot)
2017-06-25 18:58:59.065  INFO 10640 --- [           main] com.likeoak.SpringBootExample            : No active profile set, falling back to default profiles: default
2017-06-25 18:58:59.107  INFO 10640 --- [           main] ationConfigEmbeddedWebApplicationContext : Refreshing org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext@6b8ca3c8: startup date [Sun Jun 25 18:58:59 CST 2017]; root of context hierarchy
2017-06-25 18:59:00.581  INFO 10640 --- [           main] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat initialized with port(s): 8080 (http)
2017-06-25 18:59:00.597  INFO 10640 --- [           main] o.apache.catalina.core.StandardService   : Starting service Tomcat
2017-06-25 18:59:00.598  INFO 10640 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet Engine: Apache Tomcat/8.5.11
2017-06-25 18:59:00.748  INFO 10640 --- [ost-startStop-1] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2017-06-25 18:59:00.748  INFO 10640 --- [ost-startStop-1] o.s.web.context.ContextLoader            : Root WebApplicationContext: initialization completed in 1645 ms
2017-06-25 18:59:00.900  INFO 10640 --- [ost-startStop-1] o.s.b.w.servlet.ServletRegistrationBean  : Mapping servlet: 'dispatcherServlet' to [/]
2017-06-25 18:59:00.904  INFO 10640 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'characterEncodingFilter' to: [/*]
2017-06-25 18:59:00.905  INFO 10640 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'hiddenHttpMethodFilter' to: [/*]
2017-06-25 18:59:00.905  INFO 10640 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'httpPutFormContentFilter' to: [/*]
2017-06-25 18:59:00.906  INFO 10640 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'requestContextFilter' to: [/*]
2017-06-25 18:59:01.247  INFO 10640 --- [           main] s.w.s.m.m.a.RequestMappingHandlerAdapter : Looking for @ControllerAdvice: org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext@6b8ca3c8: startup date [Sun Jun 25 18:58:59 CST 2017]; root of context hierarchy
2017-06-25 18:59:01.337  INFO 10640 --- [           main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/]}" onto java.lang.String com.likeoak.SpringBootExample.home()
2017-06-25 18:59:01.342  INFO 10640 --- [           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)
2017-06-25 18:59:01.342  INFO 10640 --- [           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)
2017-06-25 18:59:01.376  INFO 10640 --- [           main] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/webjars/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2017-06-25 18:59:01.376  INFO 10640 --- [           main] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2017-06-25 18:59:01.452  INFO 10640 --- [           main] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/**/favicon.ico] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2017-06-25 18:59:01.669  INFO 10640 --- [           main] o.s.j.e.a.AnnotationMBeanExporter        : Registering beans for JMX exposure on startup
2017-06-25 18:59:01.760  INFO 10640 --- [           main] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat started on port(s): 8080 (http)
2017-06-25 18:59:01.764  INFO 10640 --- [           main] com.likeoak.SpringBootExample            : Started SpringBootExample in 3.182 seconds (JVM running for 3.816)

然后访问 http://localhost:8080/
结果：
Hello World!

七、创建可执行的jar

这里通过maven插件来实现，在pom.xml中引入spring-boot-maven-plugin

  <!-- 可执行jar-->
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

执行mvn package

[INFO] Scanning for projects...
[INFO]                                                                         
[INFO] ------------------------------------------------------------------------
[INFO] Building springboot 1.0.0
[INFO] ------------------------------------------------------------------------
[INFO] 
[INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ springboot ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] Copying 0 resource
[INFO] Copying 1 resource
[INFO] 
[INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ springboot ---
[INFO] Nothing to compile - all classes are up to date
[INFO] 
[INFO] --- maven-resources-plugin:2.6:testResources (default-testResources) @ springboot ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] skip non existing resourceDirectory G:\Mybook\springBoot\src\test\resources
[INFO] 
[INFO] --- maven-compiler-plugin:3.1:testCompile (default-testCompile) @ springboot ---
[INFO] Nothing to compile - all classes are up to date
[INFO] 
[INFO] --- maven-surefire-plugin:2.18.1:test (default-test) @ springboot ---
[INFO] No tests to run.
[INFO] 
[INFO] --- maven-jar-plugin:2.6:jar (default-jar) @ springboot ---
[INFO] 
[INFO] --- spring-boot-maven-plugin:1.5.2.RELEASE:repackage (default) @ springboot ---
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 1.790 s
[INFO] Finished at: 2017-06-25T19:47:08+08:00
[INFO] Final Memory: 19M/226M
[INFO] ------------------------------------------------------------------------

打包之后，再target下面会出现spring-1.0.0.jar包

运行：
java -jar spring-1.0.0.jar

后续会继续推出这一系列spring boot的文章

本人网站：一起学JAVA

一起学JAVA之《spring boot》02-开发您的第一个S

一、导航

二、开发之前环境检查

三、创建pom.xml并导入依赖

四、编写代码

五、代码解释

六、运行代码

七、创建可执行的jar

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我爱编程

一起学JAVA之《spring boot》02-开发您的第一个S

一、导航

二、开发之前环境检查

三、创建pom.xml并导入依赖

四、编写代码

五、代码解释

六、运行代码

七、 创建可执行的jar

相关文章

网友评论

延伸阅读

深度阅读

栏目导航

热点阅读

我爱编程

七、创建可执行的jar