spring boot学习总结（一）-- 基础入门 Hello,spring boot!

写在最前

SpringBoot是伴随着Spring4.0诞生的；

从字面理解，Boot是引导的意思，因此SpringBoot帮助开发者快速搭建Spring框架；

SpringBoot帮助开发者快速启动一个Web容器；

SpringBoot继承了原有Spring框架的优秀基因；

SpringBoot简化了使用Spring的过程。

SpringBoot使编码变简单，使配置变简单，使部署变简单，使监控变简单

下面正式开始！！！快速入门！！！

1、构建Maven项目

（1）访问 http://start.spring.io/，填写信息，选择版本

（2）点击 Switch to the full version

（3）选择适合的 Java Version

（4）点击 Generate Project，下载项目，可以得到项目压缩包

（5）解压项目压缩包，然后Import

完整的项目结构（除了controller包是下面第2步手动建的之外，其他都是下载后就有的）

打开pom.xml，可以看到下列代码

<?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.lmei</groupId>
    <artifactId>SpringBoot01</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>war</packaging>

    <name>SpringBoot01</name>
    <description>Demo project for Spring Boot</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.5.4.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.7</java.version>
    </properties>

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

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-tomcat</artifactId>
            <scope>provided</scope>
        </dependency>

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

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

</project>

Import项目后，如果pom.xml报错，重新保存，让它重新加载。

加载成功后，pom.xml不再报错，但项目报错“Could not calculate build plan..."

右键项目->Maven->Update Project Configuration

2、测试

新建一个HelloController.java

package com.lmei.SpringBoot01.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.ResponseBody;

@Controller
@EnableAutoConfiguration
public class HelloController {

    @RequestMapping("/hello")
    @ResponseBody
    public String home() {
        return "Hello ,spring boot!";
    }

    public static void main(String[] args) throws Exception {
        SpringApplication.run(HelloController.class, args);
        //运行之后在浏览器中访问：http://localhost:8080/hello
    }
}

运行，HelloController右键->Run As->Java Application

控制台输出：

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v1.5.4.RELEASE)

-- ::59.840  INFO  --- [           main] c.l.S.controller.HelloController         : Starting HelloController on USER-PC with PID  (D:\workspace_spring\SpringBoot01\target\classes started by USER in D:\workspace_spring\SpringBoot01)
-- ::59.840  INFO  --- [           main] c.l.S.controller.HelloController         : No active profile set, falling back to default profiles: default
-- ::59.902  INFO  --- [           main] ationConfigEmbeddedWebApplicationContext : Refreshing org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext@524b19: startup date [Sat Jul  :: CST ]; root of context hierarchy
-- ::01.961  INFO  --- [           main] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat initialized with port(s):  (http)
-- ::01.977  INFO  --- [           main] o.apache.catalina.core.StandardService   : Starting service [Tomcat]
-- ::01.977  INFO  --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet Engine: Apache Tomcat/8.5.
-- ::02.196  INFO  --- [ost-startStop-] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
-- ::02.196  INFO  --- [ost-startStop-] o.s.web.context.ContextLoader            : Root WebApplicationContext: initialization completed in  ms
-- ::02.446  INFO  --- [ost-startStop-] o.s.b.w.servlet.ServletRegistrationBean  : Mapping servlet: 'dispatcherServlet' to [/]
-- ::02.462  INFO  --- [ost-startStop-] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'characterEncodingFilter' to: [/*]
2017-07-22 20:11:02.462  INFO 6484 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'hiddenHttpMethodFilter' to: [/*]
2017-07-22 20:11:02.462  INFO 6484 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'httpPutFormContentFilter' to: [/*]
2017-07-22 20:11:02.462  INFO 6484 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'requestContextFilter' to: [/*]
2017-07-22 20:11:02.898  INFO 6484 --- [           main] s.w.s.m.m.a.RequestMappingHandlerAdapter : Looking for @ControllerAdvice: org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext@524b19: startup date [Sat Jul 22 20:10:59 CST 2017]; root of context hierarchy
2017-07-22 20:11:03.008  INFO 6484 --- [           main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/hello]}" onto java.lang.String com.lmei.SpringBoot01.controller.HelloController.home()
2017-07-22 20:11:03.008  INFO 6484 --- [           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)
2017-07-22 20:11:03.008  INFO 6484 --- [           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)
2017-07-22 20:11:03.071  INFO 6484 --- [           main] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/webjars/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2017-07-22 20:11:03.071  INFO 6484 --- [           main] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2017-07-22 20:11:03.133  INFO 6484 --- [           main] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/**/favicon.ico] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
-- ::03.352  INFO  --- [           main] o.s.j.e.a.AnnotationMBeanExporter        : Registering beans for JMX exposure on startup
-- ::03.445  INFO  --- [           main] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat started on port(s):  (http)
-- ::03.445  INFO  --- [           main] c.l.S.controller.HelloController         : Started HelloController in 4.137 seconds (JVM running for 4.651)
-- ::39.768  INFO  --- [nio--exec-] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring FrameworkServlet 'dispatcherServlet'
-- ::39.769  INFO  --- [nio--exec-] o.s.web.servlet.DispatcherServlet        : FrameworkServlet 'dispatcherServlet': initialization started
-- ::39.819  INFO  --- [nio--exec-] o.s.web.servlet.DispatcherServlet        : FrameworkServlet 'dispatcherServlet': initialization completed in  ms

然后在浏览器访问：http://localhost:8080/hello

运行时，可能会出现的错误

unable to start embedded container; nested exception is java.lang.NoSuchMethodError: 
org.apache.tomcat.util.scan.StandardJarScanner.setJarScanFilter(Lorg/apache/tomcat/JarScanFilter;

完整的错误信息如下：

org.springframework.context.ApplicationContextException: Unable to start embedded container; nested exception is java.lang.NoSuchMethodError: org.apache.tomcat.util.scan.StandardJarScanner.setJarScanFilter(Lorg/apache/tomcat/JarScanFilter;)V
    at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.onRefresh(EmbeddedWebApplicationContext.java:) ~[spring-boot-1.5..RELEASE.jar:1.5..RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:) ~[spring-context-4.3..RELEASE.jar:4.3..RELEASE]
    at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.refresh(EmbeddedWebApplicationContext.java:) ~[spring-boot-1.5..RELEASE.jar:1.5..RELEASE]
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:) [spring-boot-1.5..RELEASE.jar:1.5..RELEASE]
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:) [spring-boot-1.5..RELEASE.jar:1.5..RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:) [spring-boot-1.5..RELEASE.jar:1.5..RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:) [spring-boot-1.5..RELEASE.jar:1.5..RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:) [spring-boot-1.5..RELEASE.jar:1.5..RELEASE]
    at com.lmei.SpringBoot01.controller.HelloController.main(HelloController.java:) [classes/:na]
Caused by: java.lang.NoSuchMethodError: org.apache.tomcat.util.scan.StandardJarScanner.setJarScanFilter(Lorg/apache/tomcat/JarScanFilter;)V
    at org.springframework.boot.context.embedded.tomcat.SkipPatternJarScanner$Tomcat8TldSkipSetter.setSkipPattern(SkipPatternJarScanner.java:) ~[spring-boot-1.5..RELEASE.jar:1.5..RELEASE]
    at org.springframework.boot.context.embedded.tomcat.SkipPatternJarScanner.setPatternToTomcat8SkipFilter(SkipPatternJarScanner.java:) ~[spring-boot-1.5..RELEASE.jar:1.5..RELEASE]
    at org.springframework.boot.context.embedded.tomcat.SkipPatternJarScanner.<init>(SkipPatternJarScanner.java:) ~[spring-boot-1.5..RELEASE.jar:1.5..RELEASE]
    at org.springframework.boot.context.embedded.tomcat.SkipPatternJarScanner.apply(SkipPatternJarScanner.java:) ~[spring-boot-1.5..RELEASE.jar:1.5..RELEASE]
    at org.springframework.boot.context.embedded.tomcat.TomcatEmbeddedServletContainerFactory.prepareContext(TomcatEmbeddedServletContainerFactory.java:) ~[spring-boot-1.5..RELEASE.jar:1.5..RELEASE]
    at org.springframework.boot.context.embedded.tomcat.TomcatEmbeddedServletContainerFactory.getEmbeddedServletContainer(TomcatEmbeddedServletContainerFactory.java:) ~[spring-boot-1.5..RELEASE.jar:1.5..RELEASE]
    at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.createEmbeddedServletContainer(EmbeddedWebApplicationContext.java:) ~[spring-boot-1.5..RELEASE.jar:1.5..RELEASE]
    at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.onRefresh(EmbeddedWebApplicationContext.java:) ~[spring-boot-1.5..RELEASE.jar:1.5..RELEASE]
    ...  common frames omitted

出错的原因是因为配置的时候不小心把tomcat配置进去，去掉就可以

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