1. 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  
01  import java.io.IOException;  
02  import java.util.Iterator;  
03  import javax.servlet.Filter;  
04  import javax.servlet.FilterChain;  
05  import javax.servlet.FilterConfig;  
06  import javax.servlet.ServletException;  
07  import javax.servlet.ServletRequest;  
08  import javax.servlet.ServletResponse;  
09  import javax.servlet.http.HttpServletRequest;  
10  import javax.servlet.http.HttpServletResponse;  
11  /** 
12  * 通过Filter过滤器来防SQL注入攻击 
13  * 
14  */  
15  public class SQLFilter implements Filter {  
16 private String inj_str = "'|and|exec|insert|select|delete|update|count|*|%
|chr|mid|master|truncate|char|declare|;|or|-|+|,";  
17  protected FilterConfig filterConfig = null;  
18  /** 
19  * Should a character encoding specified by the client be ignored? 
20  */  
21  protected boolean ignore = true;  
22  public void init(FilterConfig config) throws ServletException {  
23  this.filterConfig = config;  
24  this.inj_str = filterConfig.getInitParameter("keywords");  
25  }  
26  public void doFilter(ServletRequest request, ServletResponse response,  
27  FilterChain chain) throws IOException, ServletException {  
28  HttpServletRequest req = (HttpServletRequest)request;  
29  HttpServletResponse res = (HttpServletResponse)response;  
30  Iterator values = req.getParameterMap().values().iterator();//获取所有的表单参数  
31  while(values.hasNext()){  
32  String[] value = (String[])values.next();  
33  for(int i = 0;i < value.length;i++){  
34  if(sql_inj(value[i])){  
35  //TODO这里发现sql注入代码的业务逻辑代码  
36  return;  
37  }  
38  }  
39  }  
40  chain.doFilter(request, response);  
41  }  
42  public boolean sql_inj(String str)  
43  {  
44  String[] inj_stra=inj_str.split("\\|");  
45  for (int i=0 ; i < inj_stra.length ; i++ )  
46  {  
47  if (str.indexOf(" "+inj_stra[i]+" ")>=0)  
48  {  
49  return true;  
50  }  
51  }  
52  return false;  
53  }  
54  }  
  
也可以单独在需要防范SQL注入的JavaBean的字段上过滤：  
1   /** 
2   * 防止sql注入 
3   * 
4   * @param sql 
5   * @return 
6   */  
7   public static String TransactSQLInjection(String sql) {  
8   return sql.replaceAll(".*([';]+|(--)+).*", " ");  
9   }