java 代码实现xssFilter

以下是一个基本的Java代码实现XSS过滤器的示例：

import java.util.regex.Pattern;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;

public class XSSFilterRequestWrapper extends HttpServletRequestWrapper {

    public XSSFilterRequestWrapper(HttpServletRequest servletRequest) {
        super(servletRequest);
    }

    @Override
    public String[] getParameterValues(String parameter) {
        String[] values = super.getParameterValues(parameter);
        if (values == null) {
            return null;
        }

        int count = values.length;
        String[] encodedValues = new String[count];
        for (int i = 0; i < count; i++) {
            encodedValues[i] = xssClean(values[i]);
        }

        return encodedValues;
    }

    @Override
    public String getParameter(String parameter) {
        String value = super.getParameter(parameter);
        return xssClean(value);
    }

    @Override
    public String getHeader(String name) {
        String value = super.getHeader(name);
        return xssClean(value);
    }

    private String xssClean(String value) {
        if (value != null) {
            // 防止脚本注入
            Pattern scriptPattern = Pattern.compile("<script>(.*?)</script>", Pattern.CASE_INSENSITIVE);
            value = scriptPattern.matcher(value).replaceAll("");

            // 防止表单重定向
            scriptPattern = Pattern.compile("src[\r\n]*=[\r\n]*\\\'(.*?)\\\'", Pattern.CASE_INSENSITIVE | Pattern.MULTILINE | Pattern.DOTALL);
            value = scriptPattern.matcher(value).replaceAll("");

            scriptPattern = Pattern.compile("src[\r\n]*=[\r\n]*\\\"(.*?)\\\"", Pattern.CASE_INSENSITIVE | Pattern.MULTILINE | Pattern.DOTALL);
            value = scriptPattern.matcher(value).replaceAll("");

            // 防止脚本注入
            scriptPattern = Pattern.compile("</script>", Pattern.CASE_INSENSITIVE);
            value = scriptPattern.matcher(value).replaceAll("");

            scriptPattern = Pattern.compile("<script(.*?)>", Pattern.CASE_INSENSITIVE | Pattern.MULTILINE | Pattern.DOTALL);
            value = scriptPattern.matcher(value).replaceAll("");

            scriptPattern = Pattern.compile("eval\\((.*?)\\)", Pattern.CASE_INSENSITIVE | Pattern.MULTILINE | Pattern.DOTALL);
            value = scriptPattern.matcher(value).replaceAll("");

            scriptPattern = Pattern.compile("expression\\((.*?)\\)", Pattern.CASE_INSENSITIVE | Pattern.MULTILINE | Pattern.DOTALL);
            value = scriptPattern.matcher(value).replaceAll("");

            // 防止HTML标签注入
            scriptPattern = Pattern.compile("<", Pattern.CASE_INSENSITIVE);
            value = scriptPattern.matcher(value).replaceAll("&lt;");

            scriptPattern = Pattern.compile(">", Pattern.CASE_INSENSITIVE);
            value = scriptPattern.matcher(value).replaceAll("&gt;");
        }
        return value;
    }
}

这个过滤器实现了`javax.servlet.http.HttpServletRequestWrapper`接口，重写了三个方法：

- `getParameterValues`：过滤所有参数值并返回过滤后的结果数组。
- `getParameter`：过滤单个参数值并返回过滤后的结果。
- `getHeader`：过滤HTTP头部并返回过滤后的结果。

它使用正则表达式来替换所有可能的XSS攻击代码，并将结果返回给调用者。使用该过滤器可以大大提高应用程序的安全性。