1. 问题背景
在Spring Boot项目中，需要手动返回404异常给前端。为此，我创建了一个自定义的404异常类UnauthorizedAccessException，并在全局异常处理器GlobalExceptionHandler中处理该异常。然而，在使用Postman测试时，返回的仍然是500错误，而不是预期的404错误。
2. 代码实现
2.1 自定义404异常类
java
package cn.jbolt.config.exception;
import org.springframework.http.HttpStatus;
import org.springframework.web.bind.annotation.ResponseStatus;
/**
* 自定义无权限访问的异常
*/
@ResponseStatus(HttpStatus.NOT_FOUND)
public class UnauthorizedAccessException extends RuntimeException {
private final HttpStatus status;
public UnauthorizedAccessException(String message) {
super(message);
this.status = HttpStatus.NOT_FOUND;
}
public HttpStatus getStatus() {
return status;
}
}2.2 全局异常处理器
java
package cn.jbolt.config.exception;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.*;
@RestControllerAdvice
public class GlobalExceptionHandler {
@ExceptionHandler(UnauthorizedAccessException.class)
public ResponseEntity<String> handleUnauthorizedAccessException(UnauthorizedAccessException ex) {
System.out.println("UnauthorizedAccessException-------------------------: " + ex.getMessage());
HttpStatus status = ex.getStatus();
String message = ex.getMessage();
return new ResponseEntity<>(message, status);
}
}2.3 过滤器中抛出自定义异常
java
package cn.jbolt.teaching_tools.school;
import cn.jbolt.config.exception.UnauthorizedAccessException;
import cn.jbolt.teaching_tools.school.entity.School;
import cn.jbolt.teaching_tools.school.service.SchoolService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.core.Ordered;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;
import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
@Component
@Order(Ordered.HIGHEST_PRECEDENCE)
public class SchoolContextFilter implements Filter {
@Autowired
private SchoolService schoolService;
@Override
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
throws IOException, ServletException {
HttpServletRequest httpRequest = (HttpServletRequest) request;
HttpServletResponse httpResponse = (HttpServletResponse) response;
try {
// 从域名获取学校信息
String serverName = httpRequest.getServerName();
String[] domainParts = serverName.split("\\.");
if (domainParts.length >= 3) {
String subdomain = domainParts[0];
// 查询学校ID
School school = schoolService.getByDomain(subdomain);
if (school != null) {
// 设置到SchoolContextHolder和请求属性
SchoolContextHolder.setSchoolId(school.getId().toString());
} else {
// 如果找不到学校，抛出异常
throw new UnauthorizedAccessException("异常域名");
}
} else {
// 如果不是二级域名，抛出异常
throw new UnauthorizedAccessException("异常域名");
}
chain.doFilter(request, response);
} catch (UnauthorizedAccessException ex) {
// 手动处理异常，写入响应
httpResponse.setStatus(HttpStatus.NOT_FOUND.value());
httpResponse.setContentType("application/json;charset=UTF-8");
httpResponse.getWriter().write("{\"timestamp\": " + System.currentTimeMillis() + ", \"status\": 404, \"error\": \"Not Found\", \"message\": \"" + ex.getMessage() + "\", \"path\": \"" + httpRequest.getRequestURI() + "\"}");
} finally {
SchoolContextHolder.clear();
}
}
}3. 问题分析
3.1 Filter抛出的异常未被Spring MVC捕获
在Spring Boot中，Filter是Servlet API的一部分，而Spring MVC的全局异常处理器（@ControllerAdvice或@RestControllerAdvice）只能捕获Spring MVC控制器中抛出的异常。因此，当Filter抛出异常时，Spring MVC的全局异常处理器无法捕获，导致返回了500错误。
3.2 @RestControllerAdvice未正确扫描
如果GlobalExceptionHandler类所在的包没有被Spring Boot扫描到，它将无法生效。确保GlobalExceptionHandler类所在的包在Spring Boot的扫描路径内。
3.3 Spring Boot的默认错误处理机制
Spring Boot的默认错误处理机制可能会覆盖自定义的异常处理逻辑。可以通过配置application.properties或application.yml文件来调整默认错误处理行为。
4. 解决方案
4.1 在Filter中手动处理异常
由于Filter抛出的异常无法被Spring MVC的全局异常处理器捕获，因此需要在Filter中手动处理异常，将异常信息写入响应中。具体实现如下：
javascript
@Override
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
throws IOException, ServletException {
HttpServletRequest httpRequest = (HttpServletRequest) request;
HttpServletResponse httpResponse = (HttpServletResponse) response;
try {
// 从域名获取学校信息
String serverName = httpRequest.getServerName();
String[] domainParts = serverName.split("\\.");
if (domainParts.length >= 3) {
String subdomain = domainParts[0];
// 查询学校ID
School school = schoolService.getByDomain(subdomain);
if (school != null) {
// 设置到SchoolContextHolder和请求属性
SchoolContextHolder.setSchoolId(school.getId().toString());
} else {
// 如果找不到学校，抛出异常
throw new UnauthorizedAccessException("异常域名");
}
} else {
// 如果不是二级域名，抛出异常
throw new UnauthorizedAccessException("异常域名");
}
chain.doFilter(request, response);
} catch (UnauthorizedAccessException ex) {
// 手动处理异常，写入响应
httpResponse.setStatus(HttpStatus.NOT_FOUND.value());
httpResponse.setContentType("application/json;charset=UTF-8");
httpResponse.getWriter().write("{\"timestamp\": " + System.currentTimeMillis() + ", \"status\": 404, \"error\": \"Not Found\", \"message\": \"" + ex.getMessage() + "\", \"path\": \"" + httpRequest.getRequestURI() + "\"}");
} finally {
SchoolContextHolder.clear();
}
}4.2 确保@RestControllerAdvice被正确扫描
确保GlobalExceptionHandler类所在的包在Spring Boot的扫描路径内。例如：
java
@SpringBootApplication(scanBasePackages = "cn.jbolt")
public class Application {
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
}4.3 调整Spring Boot的默认错误处理机制
可以通过配置application.properties或application.yml文件来调整默认错误处理行为。例如：
XML
server.error.include-stacktrace=never
server.error.include-message=always
server.error.include-binding-errors=always
server.error.include-exception=false5. 测试验证
5.1 测试用例
使用Postman测试以下两种场景：
-
正常请求：请求的域名和路径符合预期，应返回正常响应。
-
异常请求：请求的域名不符合预期，应返回404错误。
5.2 测试结果
-
正常请求：返回正常响应。
-
异常请求：返回404错误，响应内容如下：
{ "timestamp": 1745483881203, "status": 404, "error": "Not Found", "message": "异常域名", "path": "/auth/login" }
6. 注意事项
6.1 异常处理的优先级
如果项目中有多个全局异常处理器，可能会导致异常处理逻辑被覆盖。确保自定义的异常处理逻辑优先级高于其他全局异常处理器。
6.2 日志记录
在全局异常处理器中添加日志记录，方便调试和排查问题。例如：
@ExceptionHandler(UnauthorizedAccessException.class)
public ResponseEntity<String> handleUnauthorizedAccessException(UnauthorizedAccessException ex) {
System.out.println("UnauthorizedAccessException-------------------------: " + ex.getMessage());
HttpStatus status = ex.getStatus();
String message = ex.getMessage();
return new ResponseEntity<>(message, status);
}6.3 响应格式的统一
确保返回的响应格式与前端的要求一致。可以使用统一的错误响应类来封装错误信息，例如：
public class ErrorResponse {
private Long timestamp;
private int status;
private String error;
private String message;
private String path;
// Getters and Setters
}然后在Filter中返回统一的错误响应：
httpResponse.getWriter().write(new ObjectMapper().writeValueAsString(new ErrorResponse(System.currentTimeMillis(), 404, "Not Found", ex.getMessage(), httpRequest.getRequestURI())));7. 总结
通过在Filter中手动处理异常，确保返回给前端的响应是正确的404错误，而不是500错误。