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

使用spring项目访问后台接口时返回了这个错误。

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

Fri Oct 25 17:31:57 CST 2019
There was an unexpected error (type=Not Found, status=404).
No message available

后台是这样

@Controller
@EnableAutoConfiguration
@RequestMapping("/test")
public class TestController {
	
	@RequestMapping("/testMethod")
	public JSON testMethod() {
		System.out.println("12345");
		Map res = new HashMap();
		res.put("data", 321);
		return JSONObject.fromObject(res);
	}
	
}

通过后台查看发现，请求确实收到了，但是依然报404 。最后发现是没有设置@ResponseBody。

解决方法，方法上面加上注解@ResponseBody，或者将类的注解@Controller改为@RestController。

@RestController = @Controller + @ResponseBody

修改后的代码

@Controller
@EnableAutoConfiguration
@RequestMapping("/test")
public class TestController {
	
	@RequestMapping("/testMethod")
	@ResponseBody
	public JSON testMethod() {
		System.out.println("12345");
		Map res = new HashMap();
		res.put("data", 321);
		return JSONObject.fromObject(res);
	}
	
}

或者

@RestController
@EnableAutoConfiguration
@RequestMapping("/test")
public class TestController {
	
	@RequestMapping("/testMethod")
	public JSON testMethod() {
		System.out.println("12345");
		Map res = new HashMap();
		res.put("data", 321);
		return JSONObject.fromObject(res);
	}
	
}