Spring Boot+Gradle项目ModelAndView为空，访问控制器出现白标错误页

Hey there! Let’s break down why you’re hitting that white label error and seeing an empty ModelAndView when accessing /firstapp—I’ve been in this spot before, so let’s work through it systematically.

First, Check Your Core Dependencies #

The most common gotcha here is missing the web starter dependency in your build.gradle. Without it, Spring Boot won’t set up the web infrastructure needed to handle controller requests. Double-check that your build.gradle has this line:

implementation 'org.springframework.boot:spring-boot-starter-web'

If you’re trying to render views (like using ModelAndView to load an HTML page), you’ll also need a template engine starter. For example, if you’re using Thymeleaf:

implementation 'org.springframework.boot:spring-boot-starter-thymeleaf'

Verify Your Controller Annotations #

Mixing up @Controller and @RestController is a super common mistake:

• Use @Controller if you want to return a view (like an HTML page via ModelAndView). This requires a template engine to resolve the view name.
• Use @RestController (or add @ResponseBody to your method) if you want to return raw text/JSON directly as the response body.

Here’s a correct example for a view-based controller:

@Controller
public class FirstAppController {
    @GetMapping("/firstapp")
    public ModelAndView loadFirstAppPage() {
        ModelAndView mav = new ModelAndView("firstapp"); // Matches src/main/resources/templates/firstapp.html (for Thymeleaf)
        mav.addObject("greeting", "Welcome to your first app!");
        return mav;
    }
}

And for a raw string response:

@RestController
public class FirstAppController {
    @GetMapping("/firstapp")
    public String getFirstAppResponse() {
        return "Hello from your first Spring Boot app!";
    }
}

Ensure Your Controller Is Being Scanned #

Spring Boot automatically scans components (like controllers) in the same package as your main application class, and all its sub-packages. If your controller is in a completely separate package, Spring won’t find it.

For example:

• If your main class is in com.example.firstapp, your controller should be in com.example.firstapp or com.example.firstapp.controller.
• If it’s outside that scope, add @ComponentScan to your main class to specify the extra packages:

@SpringBootApplication
@ComponentScan(basePackages = {"com.example.firstapp", "com.other.controller.package"})
public class FirstAppApplication {
    public static void main(String[] args) {
        SpringApplication.run(FirstAppApplication.class, args);
    }
}

Check Your Application Properties #

Double-check application.properties for any settings that might change your request path:

• If you set server.servlet.context-path=/myapp, you’ll need to access http://localhost:8080/myapp/firstapp instead of just /firstapp.
• If you changed server.port to something other than 8080, make sure you’re using the correct port in your browser.

Validate the Controller Mapping in Logs #

When you start your application, look for a log line like this:

Mapped "{[/firstapp]}" onto public org.springframework.web.servlet.ModelAndView com.example.firstapp.controller.FirstAppController.loadFirstAppPage()

If you don’t see this line, your controller isn’t being registered—go back and check the annotations or package scanning.

Quick Test to Rule Out Issues #

To isolate the problem, try creating a super simple @RestController with a basic mapping and see if it works. If it does, the issue is likely with your view setup or ModelAndView configuration. If not, it’s a core web setup or scanning problem.

内容的提问来源于stack exchange，提问作者Alhajras Algdairy