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 }