《Springboot极简教程》问题解决：Springboot启动报错 Whitelabel Error Page： This application has no explicit mapping for

Whitelabel Error Page
This application has no explicit mapping for /error, so you are seeing this as a fallback.
Tue Mar 28 22:25:43 CST 2017
There was an unexpected error (type=Internal Server Error, status=500).
Circular view path [login]: would dispatch back to the current handler URL [/login] again. Check your ViewResolver setup! (Hint: This may be the result of an unspecified view, due to default view name generation.)

首先，这个出错页面是SpringBoot的一个默认出错页面。源码在：org.springframework.boot.autoconfigure.web.servlet.error.ErrorMvcAutoConfiguration 第151行。
这种错误一般是配置错误，或者MVC报错引起的错误。
比如说，在newer versions of Spring, following needs to be put in application.properties file:

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

Also, JSP files need to be put under src/main/resources/META-INF/resources/WEB-INF/jsp

推荐直接使用java代码配置的方式，这样方便看代码：

package com.restfiddle.config;

import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.ViewResolverRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;

/**
 * Created by jack on 2017/3/28.
 *
 * @author jack
 * @date 2017/03/28
 */
@Configuration
public class WebMvcConfig extends WebMvcConfigurerAdapter {

    @Override
    public void configureViewResolvers(ViewResolverRegistry registry) {
        //spring.view.prefix=/WEB-INF/jsp/
        //spring.view.suffix=.jsp
        registry.jsp("/WEB-INF/jsp/", ".jsp");
        //registry.freeMarker();
        //registry.velocity();
        //registry.groovy();
    }

}

问题参考：

http://stackoverflow.com/questions/27113452/circular-view-path-in-a-simple-spring-boot-project-with-a-controller