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)