Whitelabel Error Page

This application has no explicit mapping for /error, so you are seeing this as a fallback.

Thu Jan 31 14:19:44 CST 2019

There was an unexpected error (type=Internal Server Error, status=500).

Circular view path [hello]: would dispatch back to the current handler URL [/hello] again. Check your ViewResolver setup! (Hint: This may be the result of an unspecified view, due to default view name generation.)

由于application.properties文件位置错误导致出现了500错误。

正确路径是src/main/resources/application.properties

错误路径是src/test/resources/application.properties

更正文件路径之后，完美执行了。

三、出现404错误的原因

访问url：http://127.0.0.1:8080/hello

Whitelabel Error Page

This application has no explicit mapping for /error, so you are seeing this as a fallback.

Thu Jan 31 14:35:20 CST 2019

There was an unexpected error (type=Not Found, status=404).

No message available

出现404的错误经过排查是2个原因造成的

1、由于application.properties文件位置错误

正确路径是src/main/resources/application.properties

错误路径是src/test/resources/application.properties

2、由于application.properties文件位置错误，模板名称为helloccc.jsp时根本映射不到。

src/main/resources/application.properties修改为src/test/resources/application.properties之后测试完美执行

我为了测试写的是helloccc测试结束之后helloccc都修改成了hello

四、以下代码是修改错误之后能够正确执行的代码

1、Application.java

java;toolbar:false">package com.how2java.springboot;
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);
    }
}

2、HelloController.java

package com.how2java.springboot.web;
import java.text.DateFormat;
import java.util.Date;
 
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
  
@Controller
public class HelloController {
  
    @RequestMapping("/hello")
    public String hello(Model m) {
        m.addAttribute("now", DateFormat.getDateTimeInstance().format(new Date()));
        return "helloccc";
    }
}

3、hello.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
Hi JSP. 现在时间是 ${now}

4、application.properties

spring.mvc.view.prefix=/WEB-INF/jsp/
spring.mvc.view.suffix=.jsp

5、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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
  <groupId>com.how2java</groupId>
  <artifactId>springboot</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <name>springboot</name>
  <description>springboot</description>
  <packaging>war</packaging>
  
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.5.9.RELEASE</version>
    </parent>
    <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>
            
        </dependency>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>3.8.1</version>
      <scope>test</scope>
    </dependency>
  <!-- servlet依赖. -->
        <dependency>
              <groupId>javax.servlet</groupId>
              <artifactId>javax.servlet-api</artifactId>
              
        </dependency>
         <dependency>
              <groupId>javax.servlet</groupId>
              <artifactId>jstl</artifactId>
         </dependency>
        <!-- tomcat的支持.-->
        <dependency>
               <groupId>org.apache.tomcat.embed</groupId>
               <artifactId>tomcat-embed-jasper</artifactId>
               
        </dependency>    
    </dependencies>
    <properties>
        <java.version>1.8</java.version>
    </properties>
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

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