Spring Boot : Whitelabel Error Page解决方案

楼主最近爱上了一个新框架——Spring Boot, 搭建快还不用写一堆xml，最重要的是自带Tomcat 真是好

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.demo</groupId>
     <artifactId>Demo</artifactId>
     <version>0.0.1-SNAPSHOT</version>
     <packaging>jar</packaging>

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

     <parent>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-parent</artifactId>
         <version>1.5.9.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>1.8</java.version>
     </properties>

     <dependencies>

         <dependency>
             <groupId>org.mybatis.spring.boot</groupId>
             <artifactId>mybatis-spring-boot-starter</artifactId>
             <version>1.3.1</version>
         </dependency>

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

         <dependency>
             <groupId>org.springframework.boot</groupId>
             <artifactId>spring-boot-starter-jdbc</artifactId>
             <exclusions>
                 <exclusion>
                     <groupId>org.apache.tomcat</groupId>
                     <artifactId>tomcat-jdbc</artifactId>
                 </exclusion>
             </exclusions>
         </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>

controller.java

 package com.demo.controller;

 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.stereotype.Controller;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.ResponseBody;

 import com.demo.domain.User;
 import com.demo.service.UserService;

 @Controller
 @RequestMapping(value = "/uc")
 public class UserController {

     @Autowired
     private UserService userService;

     @ResponseBody
     @RequestMapping("/stemp.htm")
     private String sYeMian(User user){
         System.out.println("进了方法 syso");

         User u = new User();
         u.setMuBan(user.getMuBan());

         int i = userService.sYeMian(u);

         if (i>0){
             return "存储成功";
         }
             return "存储失败";
     }
 }

DemoApplication.java

 package com.demo.example.demo;

 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;

 @SpringBootApplication
 public class Demo1Application {

     public static void main(String[] args) {
         SpringApplication.run(Demo1Application.class, args);
     }
 }

然而运行之后就懵逼了

这是咋了，咋的就404了 我路径也挺对的啊 注解也都写上了啊 咋就找不到了呢？ debug吧它不进方法 看日志吧，他还不报错 这家伙给我急的 百度一下午也没解决，最后还是看官网才知道错在了那里，程序只加载Application.java所在包及其子包下的内容。

解决方案：

一、在Application类中加上@ComponentScan(basePackages = {"com.demo.controller"}) 多个之间用","分隔 当然，这样治标不治本

 package com.demo.example.demo;

 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;
 import org.springframework.context.annotation.ComponentScan;

 @SpringBootApplication
 @ComponentScan(basePackages = {"com.demo.controller"})
 public class Demo1Application {

     public static void main(String[] args) {
         SpringApplication.run(Demo1Application.class, args);
     }
 }

二、把包的目录结构修改成正确的

 package com.demo;

 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;
 import org.springframework.context.annotation.ComponentScan;

 @SpringBootApplication
 public class Demo1Application {

     public static void main(String[] args) {
         SpringApplication.run(Demo1Application.class, args);
     }
 }