Java防SQL注入，最简单的办法是杜绝SQL拼接，SQL注入攻击能得逞是因为在原有SQL语句中加入了新的逻辑，如果使用PreparedStatement来代替Statement来执行SQL语句，其后只是输入参数，SQL注入攻击手段将无效，这是因为PreparedStatement不允许在不同的插入时间改变查询的逻辑结构，大部分的SQL注入已经挡住了，在WEB层我们可以过滤用户的输入来防止SQL注入比如用Filter来过滤全局的表单参数。

import java.io.IOException;

import java.util.Iterator;

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;

/**

* 通过Filter过滤器来防SQL注入攻击

*

*/

public class SQLFilter implements Filter {

private String inj_str = "'|and|exec|insert|select|delete|update|count|*|%|chr|mid|master|truncate|char|declare|; |or|-|+|,";

protected FilterConfig filterConfig = null;

/**

* Should a character encoding specified by the client be ignored?

*/

protected boolean ignore = true;

public void init(FilterConfig config) throws ServletException {

this.filterConfig = config;

this.inj_str = filterConfig.getInitParameter("keywords");

}

public void doFilter(ServletRequest request, ServletResponse response,

FilterChain chain) throws IOException, ServletException {

HttpServletRequest req = (HttpServletRequest)request;

HttpServletResponse res = (HttpServletResponse)response;

Iterator values = req.getParameterMap().values().iterator();//获取所有的表单参数

while(values.hasNext()){

String[] value = (String[])values.next();

for(int i = 0;i < value.length;i++){

if(sql_inj(value[i])){

//TODO这里发现sql注入代码的业务逻辑代码

return;

}

}

}

chain.doFilter(request, response);

}

public boolean sql_inj(String str)

{

String[] inj_stra=inj_str.split("\\|");

for (int i=0 ; i < inj_stra.length ; i++ )

{

if (str.indexOf(" "+inj_stra[i]+" ")>=0)

{

return true;

}

}

return false;

}

}

也可以单独在需要防范SQL注入的JavaBean的字段上过滤：

/**

* 防止sql注入

*

* @param sql

* @return

*/

public static String TransactSQLInjection(String sql) {

return sql.replaceAll(".*([';]+|(--)+).*", " ");