htmlfiltertag.java

JavaWeb高级特性书中源代码

package org.it315;
import java.io.IOException;
import java.io.StringWriter;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.JspFragment;
import javax.servlet.jsp.tagext.SimpleTagSupport;

public class HtmlFilterTag extends SimpleTagSupport
{
	public void doTag() throws JspException, IOException
	{
		JspFragment fragment = this.getJspBody();
		StringWriter writer = new StringWriter(); 
		fragment.invoke(writer);
		String newbody = filter(writer.toString());
		this.getJspContext().getOut().write(newbody);
	}

	public String filter(String message)
	{
        if (message == null)
            return (null);
        char content[] = new char[message.length()];
        message.getChars(0, message.length(), content, 0);
        StringBuffer result = new StringBuffer(content.length + 50);
        for (int i = 0; i < content.length; i++) {
            switch (content[i]) {
            case '<':
                result.append("&lt;");
                break;
            case '>':
                result.append("&gt;");
                break;
            case '&':
                result.append("&amp;");
                break;
            case '"':
                result.append("&quot;");
                break;
            default:
                result.append(content[i]);
            }
        }
        return (result.toString());
	}
}