使用spring boot 在MyEclipse上创建一个简单的应用程序

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。

Spring Boot特点

1. 创建独立的Spring应用程序

2. 嵌入的Tomcat，无需部署WAR文件

3. 简化Maven配置

4. 自动配置Spring

5. 提供生产就绪型功能，如指标，健康检查和外部配置

6. 绝对没有代码生成和对XML没有要求配置

 

环境准备：

　　Myeclipse

　　jdk1.7及以上

　　maven 3.0以上

1、首先建一个maven项目，pom.xml文件内容如下代码所示：

<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/maven-v4_0_0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>cn.cpt</groupId>
    <artifactId>SpringBoot</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>SpringBoot Maven Webapp</name>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.2.5.RELEASE</version>
        <relativePath />
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <java.version>1.8</java.version>
    </properties>

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

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


</project>

2、保存之后静静等待依赖包下载完毕，接下来创建一个java类，

在src/main/java下创建一个TestSpringBoot.java类，里面添加代码如下：

 

package controller;

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

@SpringBootApplication
@RestController
public class TestSpringBoot {
    @RequestMapping("/")
    public String firstSpringBoot() {
        return "Hello World!";
    }
    
    public static void main(String[] args){
        SpringApplication.run(TestSpringBoot.class, args);
    }
}

3、直接运行main方法；它会启动内置的tomcat服务：启动后如下所示：

  .   ____          _            __ _ _
 /\ / ___'_ __ _ _(_)_ __  __ _    
( ( )\___ | '_ | '_| | '_ / _` |    
 \/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v1.2.5.RELEASE)

2018-01-17 16:20:06.722  INFO 6028 --- [           main] controller.TestSpringBoot                : Starting TestSpringBoot on 0DYF9DI9DPNWES6 with PID 6028 (started by Administrator in D:SoftwarefolderIDEMyEclipseWorkSpaceSSMSpringBoot Maven Webapp)
2018-01-17 16:20:06.831  INFO 6028 --- [           main] ationConfigEmbeddedWebApplicationContext : Refreshing org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext@5fd91a7a: startup date [Wed Jan 17 16:20:06 CST 2018]; root of context hierarchy
2018-01-17 16:20:08.077  INFO 6028 --- [           main] o.s.b.f.s.DefaultListableBeanFactory     : Overriding bean definition for bean 'beanNameViewResolver': replacing [Root bean: class [null]; scope=; abstract=false; lazyInit=false; autowireMode=3; dependencyCheck=0; autowireCandidate=true; primary=false; factoryBeanName=org.springframework.boot.autoconfigure.web.ErrorMvcAutoConfiguration$WhitelabelErrorViewConfiguration; factoryMethodName=beanNameViewResolver; initMethodName=null; destroyMethodName=(inferred); defined in class path resource [org/springframework/boot/autoconfigure/web/ErrorMvcAutoConfiguration$WhitelabelErrorViewConfiguration.class]] with [Root bean: class [null]; scope=; abstract=false; lazyInit=false; autowireMode=3; dependencyCheck=0; autowireCandidate=true; primary=false; factoryBeanName=org.springframework.boot.autoconfigure.web.WebMvcAutoConfiguration$WebMvcAutoConfigurationAdapter; factoryMethodName=beanNameViewResolver; initMethodName=null; destroyMethodName=(inferred); defined in class path resource [org/springframework/boot/autoconfigure/web/WebMvcAutoConfiguration$WebMvcAutoConfigurationAdapter.class]]
2018-01-17 16:20:09.743  INFO 6028 --- [           main] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat initialized with port(s): 9000 (http)
2018-01-17 16:20:10.247  INFO 6028 --- [           main] o.apache.catalina.core.StandardService   : Starting service Tomcat
2018-01-17 16:20:10.249  INFO 6028 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet Engine: Apache Tomcat/8.0.23
2018-01-17 16:20:10.485  INFO 6028 --- [ost-startStop-1] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2018-01-17 16:20:10.485  INFO 6028 --- [ost-startStop-1] o.s.web.context.ContextLoader            : Root WebApplicationContext: initialization completed in 3659 ms
2018-01-17 16:20:11.820  INFO 6028 --- [ost-startStop-1] o.s.b.c.e.ServletRegistrationBean        : Mapping servlet: 'dispatcherServlet' to [/]
2018-01-17 16:20:11.827  INFO 6028 --- [ost-startStop-1] o.s.b.c.embedded.FilterRegistrationBean  : Mapping filter: 'characterEncodingFilter' to: [/*]
2018-01-17 16:20:11.827  INFO 6028 --- [ost-startStop-1] o.s.b.c.embedded.FilterRegistrationBean  : Mapping filter: 'hiddenHttpMethodFilter' to: [/*]
2018-01-17 16:20:12.187  INFO 6028 --- [           main] s.w.s.m.m.a.RequestMappingHandlerAdapter : Looking for @ControllerAdvice: org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext@5fd91a7a: startup date [Wed Jan 17 16:20:06 CST 2018]; root of context hierarchy
2018-01-17 16:20:12.343  INFO 6028 --- [           main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/]}" onto public java.lang.String controller.TestSpringBoot.firstSpringBoot()
2018-01-17 16:20:12.344  INFO 6028 --- [           main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/login],methods=[GET]}" onto public java.lang.String controller.TestSpringBoot.loginGet()
2018-01-17 16:20:12.344  INFO 6028 --- [           main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/login],methods=[POST]}" onto public java.lang.String controller.TestSpringBoot.loginPost()
2018-01-17 16:20:12.348  INFO 6028 --- [           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)
2018-01-17 16:20:12.348  INFO 6028 --- [           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)
2018-01-17 16:20:12.407  INFO 6028 --- [           main] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2018-01-17 16:20:12.407  INFO 6028 --- [           main] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/webjars/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2018-01-17 16:20:12.482  INFO 6028 --- [           main] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/**/favicon.ico] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2018-01-17 16:20:12.619  INFO 6028 --- [           main] o.s.j.e.a.AnnotationMBeanExporter        : Registering beans for JMX exposure on startup
2018-01-17 16:20:12.747  INFO 6028 --- [           main] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat started on port(s): 9000 (http)
2018-01-17 16:20:12.750  INFO 6028 --- [           main] controller.TestSpringBoot                : Started TestSpringBoot in 6.666 seconds (JVM running for 7.24)

3、在网页上可输入地址localhost:8080/即可访问到firstSpringBoot()方法，在页面上显示Hello word,

（如果报错端口被占用的话可以修改内置Tomcat的端口，详情连接 http://www.cnblogs.com/caopt/p/8303662.html）

4、这是一个简单应用程序，可是为什么它运行main方法就可以了呢，让我们从源码分析一下：

运行main方法之后 SpringApplication会运行他的run方法，看下源码

/**
     * Static helper that can be used to run a {@link SpringApplication} from the
     * specified source using default settings.
     * @param source the source to load
     * @param args the application arguments (usually passed from a Java main method)
     * @return the running {@link ApplicationContext}
     */
    public static ConfigurableApplicationContext run(Object source, String... args) {
        return run(new Object[] { source }, args);
    }

    /**
     * Static helper that can be used to run a {@link SpringApplication} from the
     * specified sources using default settings and user supplied arguments.
     * @param sources the sources to load
     * @param args the application arguments (usually passed from a Java main method)
     * @return the running {@link ApplicationContext}
     */
    public static ConfigurableApplicationContext run(Object[] sources, String[] args) {
        return new SpringApplication(sources).run(args);
    }

1、它根据传过来的类会创建一个Spring应用上下文（Application Context）（通过映射的方式找到要找的东西）。另一方面它会扫描当前应用类路径上的依赖，例如本例中发现spring-webmvc（由 spring-boot-starter-web传递引入）在类路径中，那么Spring Boot会判断这是一个Web应用，并启动一个内嵌的Servlet容器（默认是Tomcat）用于处理HTTP请求。

 2、当发生请求过来之后，Spring Web Mvc框架会将Servlet容器里收到的HTTP请求根据路径分发给对应的@Controller类进行处理，@RestController是一类特殊的@Controller，它的返回值直接作为HTTP Response的Body部分返回给浏览器。

 3、多个url路径如下代码

 

package controller;

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

@SpringBootApplication
@RestController
public class TestSpringBoot {
    
    @RequestMapping(value = "/TestGet", method = RequestMethod.GET)
    public String testGet() {
        return "Hello Get";
    }

    @RequestMapping(value = "/TestPost", method = RequestMethod.POST)
    public String testPost() {
        return "Hello Post";
    }
    @RequestMapping("/")
    public String firstSpringBoot() {
        return "Hello World!";
    }
    
    public static void main(String[] args){
        SpringApplication.run(TestSpringBoot.class, args);
    }
}

 4、springBoot对调试支持很好，修改之后可以实时生效，需要添加以下的配置：

 

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-devtools</artifactId>
        <optional>true</optional>
   </dependency>
</dependencies>
<build>
    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
            <configuration>
                <fork>true</fork>
            </configuration>
        </plugin>
   </plugins>
</build>

这里需要注意的是，版本要匹配不然会报错。