Servlet 异常处理

时间 2019-12-01

原文原文链接

在 javax.servlet.HttpServlet中html

protected void doGet(HttpServletRequest req, HttpServletResponse resp)
        throws ServletException, IOException

protected void doPost(HttpServletRequest req, HttpServletResponse resp)
        throws ServletException, IOException

抛出了 ServletException 和 IOException。java

让咱们写一个简单的Servlet MyExceptionServlet 看下当咱们在web中抛出如上的异常会出现什么状况：web

package com.journaldev.servlet.exception;

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

@WebServlet("/MyExceptionServlet")
public class MyExceptionServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;

	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		throw new ServletException("GET method is not supported.");
	}

}

咱们在浏览器中发出请求 _ localhost:8080/ServletExceptionHandling/MyExceptionServlet_，获得以下响应：api

由于浏览器只能解析 HTML 文本，因此在web应用中抛出异常后，Servlet容器会将抛出的异常解析为 HTML文本对浏览器进行响应。不一样的解析会在不一样的web容器中有所不一样。以上响应是tomcat响应的结果，若是使用其它容器 JBOSS 或者 Glassfish 获得的响应会有所不一样。浏览器

以上响应将服务器商的详细的错误信息展现给用户没有任何实际意义，不利于用户操做体验和网站安全。tomcat

Servlet 异常处理

Servlet api容许们对 web异常进行自定义处理，对用户给出有效的响应。能够在web应用中给出多个异常处理类，为了简单起见，咱们只建立一个类对全部的异常和错误进行响应。安全

package com.journaldev.servlet.exception;

import java.io.IOException;
import java.io.PrintWriter;

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

@WebServlet("/AppExceptionHandler")
public class AppExceptionHandler extends HttpServlet {
	private static final long serialVersionUID = 1L;

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

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

	private void processError(HttpServletRequest request,
			HttpServletResponse response) throws IOException {
		// Analyze the servlet exception
		Throwable throwable = (Throwable) request
				.getAttribute("javax.servlet.error.exception");
		Integer statusCode = (Integer) request
				.getAttribute("javax.servlet.error.status_code");
		String servletName = (String) request
				.getAttribute("javax.servlet.error.servlet_name");
		if (servletName == null) {
			servletName = "Unknown";
		}
		String requestUri = (String) request
				.getAttribute("javax.servlet.error.request_uri");
		if (requestUri == null) {
			requestUri = "Unknown";
		}
		
		// Set response content type
	      response.setContentType("text/html");
	 
	      PrintWriter out = response.getWriter();
	      out.write("<html><head><title>Exception/Error Details</title></head><body>");
	      if(statusCode != 500){
	    	  out.write("<h3>Error Details</h3>");
	    	  out.write("<strong>Status Code</strong>:"+statusCode+"<br>");
	    	  out.write("<strong>Requested URI</strong>:"+requestUri);
	      }else{
	    	  out.write("<h3>Exception Details</h3>");
	    	  out.write("<ul><li>Servlet Name:"+servletName+"</li>");
	    	  out.write("<li>Exception Name:"+throwable.getClass().getName()+"</li>");
	    	  out.write("<li>Requested URI:"+requestUri+"</li>");
	    	  out.write("<li>Exception Message:"+throwable.getMessage()+"</li>");
	    	  out.write("</ul>");
	      }
	      
	      out.write("<br><br>");
	      out.write("<a href=\"index.html\">Home Page</a>");
	      out.write("</body></html>");
	}
}

在 web.xml 中增长以下配置:服务器

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" version="3.0">
  <display-name>ServletExceptionHandling</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
  </welcome-file-list>
  
  <error-page>
  	<error-code>404</error-code>
  	<location>/AppExceptionHandler</location>
  </error-page>
  
  <error-page>
  <exception-type>javax.servlet.ServletException</exception-type>
  <location>/AppExceptionHandler</location>
  </error-page>
</web-app>

经过如上配置，咱们此时再发出 404请求和错误请求会获得以下响应:app

1. Servlet 异常处理
2. Servlet 过滤器和异常处理
3. 处理异常：org.eclipse.jdt.internal.compiler.CompilationResult.getProblems ()
4. python异常处理_Python异常处理
5. itext常见异常处理
6. 异常与异常处理
7. 异常和异常处理
8. spring mvc 异常处理机制和统一异常处理
9. 异常处理
10. 【异常处理】
更多相关文章...
• C# 异常处理 - C#教程
• PHP 异常处理 - PHP教程
• Docker 清理命令
• 常用的分布式事务解决方案