怎樣用java servelet處理異常

小樊
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2024-09-25 15:30:33

在Java Servlet中處理異常的最佳實(shí)踐是使用全局異常處理器。這樣可以確保所有未捕獲的異常都能得到適當(dāng)?shù)奶幚?，并提供有用的錯(cuò)誤信息給用戶。以下是使用全局異常處理器處理異常的步驟：

  1. 創(chuàng)建一個(gè)自定義的異常類（可選）： 如果你需要?jiǎng)?chuàng)建一個(gè)特定的異常類來處理Servlet中的異常，可以創(chuàng)建一個(gè)新的Java類，繼承自Exception類或其他適當(dāng)?shù)漠惓ｎ悺?/p>

  2. 創(chuàng)建一個(gè)全局異常處理器類，實(shí)現(xiàn)javax.servlet.http.HttpServlet類，并重寫doGet()和doPost()方法。在這些方法中，使用try-catch語(yǔ)句捕獲異常，并處理它們。

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@WebServlet("/globalExceptionHandler")
public class GlobalExceptionHandlerServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        handleException(request, response);
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        handleException(request, response);
    }

    private void handleException(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        Integer statusCode = (Integer) request.getAttribute("javax.servlet.error.status_code");

        if (statusCode == null) {
            statusCode = HttpServletResponse.SC_INTERNAL_SERVER_ERROR;
        }

        response.setContentType("text/html;charset=UTF-8");
        response.setStatus(statusCode);

        request.setAttribute("errorMessage", "An error occurred while processing your request.");
        request.getRequestDispatcher("/errorPage.jsp").forward(request, response);
    }
}
  1. 在web.xml中配置全局異常處理器Servlet：
<servlet>
    <servlet-name>GlobalExceptionHandlerServlet</servlet-name>
    <servlet-class>com.example.GlobalExceptionHandlerServlet</servlet-class>
</servlet>

<servlet-mapping>
    <servlet-name>GlobalExceptionHandlerServlet</servlet-name>
    <url-pattern>/globalExceptionHandler</url-pattern>
</servlet-mapping>

或者在Spring Boot應(yīng)用中，使用@ControllerAdvice和@ExceptionHandler注解創(chuàng)建一個(gè)全局異常處理類：

import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.servlet.ModelAndView;

@ControllerAdvice
public class GlobalExceptionHandler {

    @ExceptionHandler(Exception.class)
    public ResponseEntity<Object> handleException(Exception ex) {
        ModelAndView modelAndView = new ModelAndView("errorPage");
        modelAndView.addObject("errorMessage", "An error occurred while processing your request.");
        return new ResponseEntity<>(modelAndView, HttpStatus.INTERNAL_SERVER_ERROR);
    }
}
  1. 在應(yīng)用中拋出異常：

當(dāng)你的Servlet或其他組件遇到異常時(shí)，將異常對(duì)象設(shè)置到請(qǐng)求屬性中，如下所示：

try {
    // Your code that might throw an exception
} catch (Exception ex) {
    request.setAttribute("javax.servlet.error.status_code", HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
    throw ex;
}

這樣，當(dāng)異常發(fā)生時(shí)，全局異常處理器將捕獲它，并返回適當(dāng)?shù)腻e(cuò)誤頁(yè)面給用戶。

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