Ajax请求和Filter配合案例解析


            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|;|--|+|,|*|/";

/*

* String badStr =

* "'|and|exec|execute|insert|create|drop|table|from|grant|use|group_concat|column_name|"

* +

* "information_schema.columns|table_schema|union|where|select|delete|update|order|by|count|*|"

* + "chr|mid|master|truncate|char|declare|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/*</url-pattern>

</filter-mapping>

<filter>



分析，ajax请求DemoServlet，然后请求先被防止SQL注入这个Filter过滤器先过滤，然后过滤到的请求参数构成一个匹配字符串，然后检查是否是恶意代码，如果是的话，请求转发。但是很遗憾，逻辑上这个是对的，但是ajax请求是局部刷新的，最后是要回到ajax请求发起的这个页面的，所以请求转发不会实现，我们看下一种实现逻辑。

思路二：返回值进行判断

这个思路的逻辑是这样的：在Filter过滤掉信息的时候，给ajax请求回送一个json数据，然后返回给前台，前台拿这个数据进行判断是否是恶意代码和良好代码。再进行下一步的处理。

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

if (data.mssage!=""){

//执行处理恶意代码的逻辑

}

else{

}

},

error:function(){

//错误之后的逻辑

}

});



防止SQL注入的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))

{

//传送json数据

JSONObject json = new JSONObject();

json.accumulate("message", "恶意代码注入");

res.getWriter().print(json.toString()); 

}

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|;|--|+|,|*|/";

/*

* String badStr =

* "'|and|exec|execute|insert|create|drop|table|from|grant|use|group_concat|column_name|"

* +

* "information_schema.columns|table_schema|union|where|select|delete|update|order|by|count|*|"

* + "chr|mid|master|truncate|char|declare|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.");

}

}



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|;|--|+|,|*|/";

/*

* String badStr =

* "'|and|exec|execute|insert|create|drop|table|from|grant|use|group_concat|column_name|"

* +

* "information_schema.columns|table_schema|union|where|select|delete|update|order|by|count|*|"

* + "chr|mid|master|truncate|char|declare|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。

以上所述是小编给大家介绍的Ajax请求和Filter配合案例解析，希望对大家有所帮助，如果大家有任何疑问请给我留言，小编会及时回复大家的。在此也非常感谢大家对中文源码网网站的支持！