使用maven构建的Spring boot项目在开始搭建的时候出的一些错误
首先，先构建一个maven项目，构建好了之后，会有一个错误,先说明一下，我生成maven项目时jre给我自动选择的是1.5版本的，而本人安装的是1.8的
然后，我们要消除这个错误，发现是缺少了一个javax.servlet这个包，因此我们在pom文件中加入了
<dependency> <groupId>javax.servlet</groupId> <artifactId>servlet-api</artifactId> <version>3.0-alpha-1</version> </dependency>
哎，发现错误消失了，好我们开始构建一个Spring boot 项目，添加一些依赖到pom中
首先，发现packaging自动生成的是war，我们把它改成
<packaging>jar</packaging>
然后开始添加Spring boot
<parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>1.5.3.RELEASE</version> </parent> <dependencies> <dependency> <groupId>javax.servlet</groupId> <artifactId>servlet-api</artifactId> <version>3.0-alpha-1</version> </dependency> <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>
需要说明的是，这个时候需要右击项目，maven，update project 更新一下
这个时候，又会有一个错误产生Java compiler level does not match the version of the installed Java project facet.
OMG,我去网上查发现他们都是没有错误，为什么就我有，不公平，不过出现错误还是要解决的
这个问题就是你编译的版本和你项目的版本不一致，怎么办？
好，我们来解决一下，右击项目properties,选择java compiler
发现是这个样子的
我们要修改成这个，选择1.5版本
好，这个错误消失了，在build path 自己版本的jre就好了，然后写一个demo
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class Application {
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
}
ok,发现挺简单的，我们试着运行一下，OMG,又出问题了
org.springframework.context.ApplicationContextException: Unable to start embedded container; nested exception is org.springframework.boot.context.embedded.EmbeddedServletContainerException: Unable to start embedded Tomcat at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.onRefresh(EmbeddedWebApplicationContext.java:137) ~[spring-boot-1.5.3.RELEASE.jar:1.5.3.RELEASE] at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:536) ~[spring-context-4.3.8.RELEASE.jar:4.3.8.RELEASE] at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.refresh(EmbeddedWebApplicationContext.java:122) ~[spring-boot-1.5.3.RELEASE.jar:1.5.3.RELEASE] at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:737) [spring-boot-1.5.3.RELEASE.jar:1.5.3.RELEASE] at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:370) [spring-boot-1.5.3.RELEASE.jar:1.5.3.RELEASE] at org.springframework.boot.SpringApplication.run(SpringApplication.java:314) [spring-boot-1.5.3.RELEASE.jar:1.5.3.RELEASE] at org.springframework.boot.SpringApplication.run(SpringApplication.java:1162) [spring-boot-1.5.3.RELEASE.jar:1.5.3.RELEASE] at org.springframework.boot.SpringApplication.run(SpringApplication.java:1151) [spring-boot-1.5.3.RELEASE.jar:1.5.3.RELEASE] at com.mts.Application.main(Application.java:9) [classes/:na] Caused by: org.springframework.boot.context.embedded.EmbeddedServletContainerException: Unable to start embedded Tomcat at org.springframework.boot.context.embedded.tomcat.TomcatEmbeddedServletContainer.initialize(TomcatEmbeddedServletContainer.java:123) ~[spring-boot-1.5.3.RELEASE.jar:1.5.3.RELEASE] at org.springframework.boot.context.embedded.tomcat.TomcatEmbeddedServletContainer.<init>(TomcatEmbeddedServletContainer.java:84) ~[spring-boot-1.5.3.RELEASE.jar:1.5.3.RELEASE] at org.springframework.boot.context.embedded.tomcat.TomcatEmbeddedServletContainerFactory.getTomcatEmbeddedServletContainer(TomcatEmbeddedServletContainerFactory.java:554) ~[spring-boot-1.5.3.RELEASE.jar:1.5.3.RELEASE] at org.springframework.boot.context.embedded.tomcat.TomcatEmbeddedServletContainerFactory.getEmbeddedServletContainer(TomcatEmbeddedServletContainerFactory.java:179) ~[spring-boot-1.5.3.RELEASE.jar:1.5.3.RELEASE] at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.createEmbeddedServletContainer(EmbeddedWebApplicationContext.java:164) ~[spring-boot-1.5.3.RELEASE.jar:1.5.3.RELEASE] at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.onRefresh(EmbeddedWebApplicationContext.java:134) ~[spring-boot-1.5.3.RELEASE.jar:1.5.3.RELEASE] ... 8 common frames omitted Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardServer[-1]] at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:167) ~[tomcat-embed-core-8.5.14.jar:8.5.14] at org.apache.catalina.startup.Tomcat.start(Tomcat.java:344) ~[tomcat-embed-core-8.5.14.jar:8.5.14] at org.springframework.boot.context.embedded.tomcat.TomcatEmbeddedServletContainer.initialize(TomcatEmbeddedServletContainer.java:99) ~[spring-boot-1.5.3.RELEASE.jar:1.5.3.RELEASE] ... 13 common frames omitted Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardService[Tomcat]] at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:167) ~[tomcat-embed-core-8.5.14.jar:8.5.14] at org.apache.catalina.core.StandardServer.startInternal(StandardServer.java:793) ~[tomcat-embed-core-8.5.14.jar:8.5.14] at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150) ~[tomcat-embed-core-8.5.14.jar:8.5.14] ... 15 common frames omitted Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Tomcat]] at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:167) ~[tomcat-embed-core-8.5.14.jar:8.5.14] at org.apache.catalina.core.StandardService.startInternal(StandardService.java:422) ~[tomcat-embed-core-8.5.14.jar:8.5.14] at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150) ~[tomcat-embed-core-8.5.14.jar:8.5.14] ... 17 common frames omitted Caused by: org.apache.catalina.LifecycleException: A child container failed during start at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:947) ~[tomcat-embed-core-8.5.14.jar:8.5.14] at org.apache.catalina.core.StandardEngine.startInternal(StandardEngine.java:262) ~[tomcat-embed-core-8.5.14.jar:8.5.14] at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150) ~[tomcat-embed-core-8.5.14.jar:8.5.14] ... 19 common frames omitted
去网上查了下资料，最后发现是前面添加的
<dependency> <groupId>javax.servlet</groupId> <artifactId>servlet-api</artifactId> <version>3.0-alpha-1</version> </dependency>
和Spring boot 冲突了，我们把上面这个
<dependency> <groupId>javax.servlet</groupId> <artifactId>servlet-api</artifactId> <version>3.0-alpha-1</version> </dependency>
删掉就好了，然后再运行一遍，发现ok没有问题了
