Question

我正在尝试部署一个非常简单的Spring Boot应用程序，在该应用程序中，导航到localhost：8080 / greetings将显示“ Spring Boot的问候！”。但是，该URL似乎不起作用。导航到链接会提示我出现空指针异常。我已经对该问题进行了一些初步研究，但以下修复方法无效：

将类从默认包中移出，并移至已定义的包中
使用@ComponentScan
将控制器类移动到应用程序类的子包中

控制器类：

package controllers;

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class HelloController {

    @RequestMapping("/greetings")
    public String index() {
        return "Greetings from Spring Boot!";
    }

}

应用程序类：

package controllers;

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);
    }
}

pom.xml

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>

<groupId>org.springframework</groupId>
<artifactId>gs-spring-boot</artifactId>
<version>0.1.0</version>

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.1.4.RELEASE</version>
</parent>

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

NullPointerExceptionError：

2019-07-02 08:03:54.290 ERROR 23960 --- [nio-8080-exec-1] o.a.c.c.C.[Tomcat].[localhost]           : Exception Processing /greetings

java.lang.NullPointerException: null
    at org.jboss.security.auth.message.config.JBossServerAuthConfig.getAuthContext(JBossServerAuthConfig.java:108) ~[picketbox-5.0.3.Final-redhat-1.jar:5.0.3.Final-redhat-1]
    at org.apache.catalina.authenticator.AuthenticatorBase.getJaspicState(AuthenticatorBase.java:662) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:566) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) [tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) [tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) [tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:408) [tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) [tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:834) [tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1415) [tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-9.0.17.jar:9.0.17]
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_211]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_211]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-9.0.17.jar:9.0.17]
    at java.lang.Thread.run(Thread.java:748) [na:1.8.0_211]

2019-07-02 08:03:54.295 ERROR 23960 --- [nio-8080-exec-1] o.a.c.c.C.[Tomcat].[localhost]           : Exception Processing ErrorPage[errorCode=0, location=/error]

java.lang.NoSuchMethodError: javax.servlet.http.HttpServletRequest.getHttpServletMapping()Ljavax/servlet/http/HttpServletMapping;
    at org.apache.catalina.core.ApplicationHttpRequest.setRequest(ApplicationHttpRequest.java:690) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.catalina.core.ApplicationHttpRequest.<init>(ApplicationHttpRequest.java:114) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.catalina.core.ApplicationDispatcher.wrapRequest(ApplicationDispatcher.java:917) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:358) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:312) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.catalina.core.StandardHostValve.custom(StandardHostValve.java:394) [tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.catalina.core.StandardHostValve.status(StandardHostValve.java:253) [tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.catalina.core.StandardHostValve.throwable(StandardHostValve.java:348) [tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:148) [tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) [tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) [tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) [tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:408) [tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) [tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:834) [tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1415) [tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-9.0.17.jar:9.0.17]
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_211]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_211]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-9.0.17.jar:9.0.17]
    at java.lang.Thread.run(Thread.java:748) [na:1.8.0_211]

2019-07-02 08:03:54.296 ERROR 23960 --- [nio-8080-exec-1] o.a.c.c.C.[Tomcat].[localhost]           : Exception Processing ErrorPage[errorCode=0, location=/error]

java.lang.NoSuchMethodError: javax.servlet.http.HttpServletRequest.getHttpServletMapping()Ljavax/servlet/http/HttpServletMapping;
    at org.apache.catalina.core.ApplicationHttpRequest.setRequest(ApplicationHttpRequest.java:690) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.catalina.core.ApplicationHttpRequest.<init>(ApplicationHttpRequest.java:114) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.catalina.core.ApplicationDispatcher.wrapRequest(ApplicationDispatcher.java:917) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:358) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:312) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.catalina.core.StandardHostValve.custom(StandardHostValve.java:394) [tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.catalina.core.StandardHostValve.status(StandardHostValve.java:253) [tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.catalina.core.StandardHostValve.throwable(StandardHostValve.java:348) [tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:173) [tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) [tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) [tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) [tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:408) [tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) [tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:834) [tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1415) [tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-9.0.17.jar:9.0.17]
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_211]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_211]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-9.0.17.jar:9.0.17]
    at java.lang.Thread.run(Thread.java:748) [na:1.8.0_211]

Answer 1

我找到了答案。原来，我需要在我的pom.xml中使<groupId>唯一

Answer 2

无论如何，在servlet容器或应用程序服务器中运行spring-boot应用程序有什么意义？

您最初发布的应用在以mvn spring-boot:run开头或以java -jar ./target/gs-spring-boot-0.1.0.jar编译后运行良好。

使用spring-boot的全部目的是拥有一个嵌入式容器，以便独立运行该应用程序。如果没有其他建议，我建议减少使用的依赖项，因为当部署到servlet容器（例如Tomcat）或应用程序服务器（例如JBoss）时，应用程序可能会更小；即在KB范围内，而不是16MB。

Spring Boot URL请求映射返回NullPointerException

2 个答案: