java防止SQL注入的几个途径

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   }