spring boot --- 初级体验

Spring boot的介绍我就不多说了，网上可以自己看一下。

它的优点就是：快！适合小白，没有复杂的配置文件。

缺点也很明显：坑有些多, 文档略少，报错有时不知道该如何处理。

下面做个最简单的入门：

首先使用maven来创建一个项目，jar即可。

假设工程名字为spring-boot

然后在pom.xml中添加如下配置：

<!-- Inherit defaults from Spring Boot -->  
<parent>  
    <groupId>org.springframework.boot</groupId>  
    <artifactId>spring-boot-starter-parent</artifactId>  
    <version>0.5.0.BUILD-SNAPSHOT</version>  
</parent>  
  
<!-- Add typical dependencies for a web application -->  
<dependencies>  
    <dependency>  
        <groupId>org.springframework.boot</groupId>  
        <artifactId>spring-boot-starter-web</artifactId>  
    </dependency>  
</dependencies>  
  
<!-- Package as an executable JAR -->  
<build>  
    <plugins>  
        <plugin>  
            <groupId>org.springframework.boot</groupId>  
            <artifactId>spring-boot-maven-plugin</artifactId>  
        </plugin>  
    </plugins>  
</build>  
  
<!-- Allow access to Spring milestones and snapshots -->  
<!-- (you don't need this if you are using anything after 0.5.0.RELEASE) -->  
<repositories>  
    <repository>  
        <id>spring-snapshots</id>  
        <url>http://repo.spring.io/snapshot</url>  
        <snapshots><enabled>true</enabled></snapshots>  
    </repository>  
    <repository>  
        <id>spring-milestones</id>  
        <url>http://repo.spring.io/milestone</url>  
        <snapshots><enabled>true</enabled></snapshots>  
    </repository>  
</repositories>  
<pluginRepositories>  
    <pluginRepository>  
        <id>spring-snapshots</id>  
        <url>http://repo.spring.io/snapshot</url>  
    </pluginRepository>  
    <pluginRepository>  
        <id>spring-milestones</id>  
        <url>http://repo.spring.io/milestone</url>  
    </pluginRepository>  
</pluginRepositories>  

之后我们创建一个controller：

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseBody;
 
@Controller
@EnableAutoConfiguration
public class SimpleController {
 
    @RequestMapping(value ="/hello", method = RequestMethod.GET)
    @ResponseBody
    public String hello(){
        return "hello world";
    }
 
    public static void main(String[] args) {
        SpringApplication.run(SimpleController.class, args);
    }
}

这个controller里有个main方法，看到没，我们直接运行即可，他会自动部署到tomcat或者jetty（8080端口不要被占用）。

然后在控制台你会看到：

  .   ____          _            __ _ _
 /\ / ___'_ __ _ _(_)_ __  __ _    
( ( )\___ | '_ | '_| | '_ / _` |    
 \/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v1.0.2.RELEASE)
 
2014-04-26 22:54:40.985  INFO 7236 --- [           main] c.r.spring.boot.SimpleController         : Starting SimpleController on rollen with PID 7236 (D:workspaceGitHubSpringDemospring-boot	argetclasses started by wenchao.ren in D:workspaceGitHubSpringDemospring-boot)
2014-04-26 22:54:41.008  INFO 7236 --- [           main] ationConfigEmbeddedWebApplicationContext : Refreshing org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext@50de0926: startup date [Sat Apr 26 22:54:41 CST 2014]; root of context hierarchy
2014-04-26 22:54:41.583  INFO 7236 --- [           main] .t.TomcatEmbeddedServletContainerFactory : Server initialized with port: 8080
2014-04-26 22:54:41.706  INFO 7236 --- [           main] o.apache.catalina.core.StandardService   : Starting service Tomcat
2014-04-26 22:54:41.706  INFO 7236 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet Engine: Apache Tomcat/7.0.52
2014-04-26 22:54:41.785  INFO 7236 --- [ost-startStop-1] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2014-04-26 22:54:41.785  INFO 7236 --- [ost-startStop-1] o.s.web.context.ContextLoader            : Root WebApplicationContext: initialization completed in 779 ms
2014-04-26 22:54:42.055  INFO 7236 --- [ost-startStop-1] o.s.b.c.e.ServletRegistrationBean        : Mapping servlet: 'dispatcherServlet' to [/]
2014-04-26 22:54:42.057  INFO 7236 --- [ost-startStop-1] o.s.b.c.embedded.FilterRegistrationBean  : Mapping filter: 'hiddenHttpMethodFilter' to: [/*]
2014-04-26 22:54:42.289  INFO 7236 --- [           main] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/**/favicon.ico] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2014-04-26 22:54:42.368  INFO 7236 --- [           main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/hello],methods=[GET],params=[],headers=[],consumes=[],produces=[],custom=[]}" onto public java.lang.String com.rollenholt.spring.boot.SimpleController.hello()
2014-04-26 22:54:42.376  INFO 7236 --- [           main] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/webjars/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2014-04-26 22:54:42.377  INFO 7236 --- [           main] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2014-04-26 22:54:42.447  INFO 7236 --- [           main] o.s.j.e.a.AnnotationMBeanExporter        : Registering beans for JMX exposure on startup
2014-04-26 22:54:42.459  INFO 7236 --- [           main] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat started on port(s): 8080/http
2014-04-26 22:54:42.460  INFO 7236 --- [           main] c.r.spring.boot.SimpleController         : Started SimpleController in 1.675 seconds (JVM running for 1.944)
2014-04-26 22:54:54.963  INFO 7236 --- [nio-8080-exec-1] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring FrameworkServlet 'dispatcherServlet'
2014-04-26 22:54:54.963  INFO 7236 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : FrameworkServlet 'dispatcherServlet': initialization started
2014-04-26 22:54:54.971  INFO 7236 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : FrameworkServlet 'dispatcherServlet': initialization completed in 8 ms

当然还有一种启动运行方式，就是通过@Configuration+@ComponentScan开启注解扫描并自动注册相应的注解Bean

import org.springframework.boot.SpringApplication;  
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;  
import org.springframework.context.annotation.ComponentScan;  
import org.springframework.context.annotation.Configuration;  
  
@Configuration  
@ComponentScan  
@EnableAutoConfiguration  
public class Application {  
    public static void main(String[] args) {  
        SpringApplication.run(Application.class);  
    }  
}  

启动完之后浏览器访问一下：http://localhost:8080/hello

就是这么快。

对于想学习/体验Spring的新手，快速建立项目模型等可以考虑用这种方式。