这篇文章主要为大家展示了“Ajax请求和Filter配合的示例分析”，内容简而易懂，条理清晰，希望能够帮助大家解决疑惑，下面让小编带领大家一起研究并学习一下“Ajax请求和Filter配合的示例分析”这篇文章吧。
案例引入
现在有这样一个问题，就是在提交大片文字评论的时候，前台拿到数据之后给后台发送ajax请求，然后后台有一个防止SQL注入的Filter，这个Filter得到这个前台传过来的数据之后，进行合法性校验，如果没有校验成功，那么要跳转到error.jsp页面进行显示错误信息。现在让我们看看怎么实现这个需求。
思路一：请求转发实现
ajax请求
$.ajax({
method:'post',
url:'servlet/DemoServlet',
dataType:'json',
data:{
'userName':userName,
'passWord':passWord,
'text': text
},
success:function(data){
//成功之后的逻辑
},
error:function(){
//错误之后的逻辑
}
});防止SQL注入Filter
package com.yiyexiaoyuan.filter;
import java.io.IOException;
import java.util.Enumeration;
import javax.security.auth.message.callback.PrivateKeyCallback.Request;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import net.sf.json.JSONObject;
//过滤sql关键字的Filter
public class SQLFilter implements Filter
{
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException
{
HttpServletRequest req = (HttpServletRequest) request;
HttpServletResponse res = (HttpServletResponse) response;
// 获得所有请求参数名
Enumeration params = req.getParameterNames();
String sql = "";
while (params.hasMoreElements())
{
// 得到参数名
String name = params.nextElement().toString();
// System.out.println("name===========================" + name +
// "--");
// 得到参数对应值
String[] value = req.getParameterValues(name);
for (int i = 0; i < value.length; i++)
{
sql = sql + value[i];
}
}
System.out.println("提交方式:"+req.getMethod());
System.out.println("被匹配字符串：" + sql);
if (sqlValidate(sql))
{
//请求转发
req.getRequestDispatcher("error.jsp").
forward(req, res);
}
else
{
String request_uri = req.getRequestURI();
chain.doFilter(request, response);
}
}
// 校验
protected static boolean sqlValidate(String str)
{
str = str.toLowerCase();// 统一转为小写
// String badStr = "and|exec";
String badStr = "'|and|exec|execute|insert|select|delete|update|count|drop|chr|mid|master|truncate|char|declare|sitename|net user|xp_cmdshell|or|like|;|--|+|,|*|/";
// 过滤掉的sql关键字，可以手动添加
String[] badStrs = badStr.split("\\|");
for (int i = 0; i < badStrs.length; i++)
{
if (str.indexOf(badStrs[i]) != -1)
{
System.out.println("匹配到：" + badStrs[i]);
return true;
}
}
return false;
}
public void init(FilterConfig filterConfig) throws ServletException
{
// throw new UnsupportedOperationException("Not supported yet.");
}
public void destroy()
{
// throw new UnsupportedOperationException("Not supported yet.");
}
}web.xml配置
<filter>
<display-name>SQLFilter</display-name>
<filter-name>SQLFilter</filter-name>
<filter-class>com.yiyexiaoyuan.filter.SQLFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>SQLFilter</filter-name>
<url-pattern>/servlet// 过滤掉的sql关键字，可以手动添加
String[] badStrs = badStr.split("\\|");
for (int i = 0; i < badStrs.length; i++)
{
if (str.indexOf(badStrs[i]) != -1)
{
System.out.println("匹配到：" + badStrs[i]);
return true;
}
}
return false;
}
public void init(FilterConfig filterConfig) throws ServletException
{
// throw new UnsupportedOperationException("Not supported yet.");
}
public void destroy()
{
// throw new UnsupportedOperationException("Not supported yet.");
}
}思路三：异常+跳转实现
这个思路的逻辑是这样的。后台的Filter过滤掉恶意注入代码的话，抛出RuntimeException()，然后导致ajax请求失败，然后回调ajax请求的error方法。但是我们错误页面的数据怎么传送过去呢？经过我认真思考之后，我们可以这样做，在session存一个error_messgae值，然后ajax请求的error方法跳转到错误页面，然后进行取值渲染错误页面。
ajax请求
$.ajax({
method:'post',
url:'servlet/DemoServlet',
dataType:'json',
data:{
'userName':userName,
'passWord':passWord,
'text': text
},
success:function(data){
//成功之后的逻辑
},
error:function(){
window.location.href="error.jsp";
}
});防止SQL注入Filter
package com.yiyexiaoyuan.filter;
import java.io.IOException;
import java.util.Enumeration;
import javax.security.auth.message.callback.PrivateKeyCallback.Request;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import net.sf.json.JSONObject;
//过滤sql关键字的Filter
public class SQLFilter implements Filter
{
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException
{
HttpServletRequest req = (HttpServletRequest) request;
HttpServletResponse res = (HttpServletResponse) response;
// 获得所有请求参数名
Enumeration params = req.getParameterNames();
String sql = "";
while (params.hasMoreElements())
{
// 得到参数名
String name = params.nextElement().toString();
// System.out.println("name===========================" + name +
// "--");
// 得到参数对应值
String[] value = req.getParameterValues(name);
for (int i = 0; i < value.length; i++)
{
sql = sql + value[i];
}
}
System.out.println("提交方式:"+req.getMethod());
System.out.println("被匹配字符串：" + sql);
if (sqlValidate(sql))
{
req.getSession().setAttribute("error_message","恶意注入了");
throw new RuntimeException("恶意注入");
}
else
{
String request_uri = req.getRequestURI();
chain.doFilter(request, response);
}
}
// 校验
protected static boolean sqlValidate(String str)
{
str = str.toLowerCase();// 统一转为小写
// String badStr = "and|exec";
String badStr = "'|and|exec|execute|insert|select|delete|update|count|drop|chr|mid|master|truncate|char|declare|sitename|net user|xp_cmdshell|or|like|;|--|+|,|*|/";
// 过滤掉的sql关键字，可以手动添加
String[] badStrs = badStr.split("\\|");
for (int i = 0; i < badStrs.length; i++)
{
if (str.indexOf(badStrs[i]) != -1)
{
System.out.println("匹配到：" + badStrs[i]);
return true;
}
}
return false;
}
public void init(FilterConfig filterConfig) throws ServletException
{
// throw new UnsupportedOperationException("Not supported yet.");
}
public void destroy()
{
// throw new UnsupportedOperationException("Not supported yet.");
}
}error.jsp实现
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>错误页面</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
</head>
<body>
<center>
系统出错了，请稍后再试......
<br />
<br />
<br />
<br />
错误信息是: ${ error_message}
</center>
</body>
</html>这样就很巧妙得实现了Filter拦截并友好提示。
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