import.java

Jodd是一个开源的公用Java基础类库

package jodd.servlet.tags.imports;

import java.io.IOException;
import java.util.ArrayList;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.jsp.tagext.TagSupport;

/**
 * Includes local resource into the current page and organize templates. It
 * can be used for including local content into the current page.<p>
 *
 * Import tag can be used for managing web templates, macros or tiles,
 * however it is called. There are 2 different types of usage:
 *
 * <ol>
 *
 * <li>Without template page. In this case every must have import for each
 * part of the page that will be loaded. When it is repeated on many pages,
 * this may become hard to maintain.
 * </li>
 *
 * <li>With templates. In this case, template is specified in an external jsp
 * file that is imported in every page that will use that template. By using
 * import parameters it is possible to manage included content.</li>
 *
 * </ol>
 *
 * Import tag is about 2x faster then default jsp:include (tomcat v5.)
 *
 */
public class Import extends TagSupport {

	private static String SERVLET_PATH = "jodd.servlet.tags.include.servlet_path";

	private boolean isPageRelative;

	private String page = "";

	public void setPage(String v) {
		page = v;
		isPageRelative = (page.startsWith("/") == false);
	}
	protected String getPage() {
		return page;
	}

	private ArrayList attrs;
	public void addAttributeName(String s) {
		attrs.add(s);
	}

	/**
	 * Evaluate tag content.
	 *
	 * @return EVAL_BODY_INCLUDE
	 */
	public int doStartTag() {
		attrs = new ArrayList();
		return EVAL_BODY_AGAIN;
	}


	/**
	 * Finds and renders imported resource. A resource (page) can be specified
	 * relatively (when it doesn't start with a slash) or absolutely from the
	 * application root (when it starts with the slash). <p>
	 *
	 * This method will be called after tag process any existing param
	 * parameters.
	 *
	 * @return EVAL_PAGE
	 */
	public int doEndTag() {
		HttpServletRequest request = (HttpServletRequest)pageContext.getRequest();
		try {
			RequestDispatcher rd = null;
			boolean first = false;						// indicates topmost servlet
			String sp = "";
			String targetUrl = new String(page);
			
			if (isPageRelative == true) {
				sp = (String) request.getAttribute(SERVLET_PATH);
				if (sp == null) {
					first = true;
					sp = request.getServletPath();
					sp = sp.substring(0, sp.lastIndexOf('/'));
				}
				targetUrl = sp + '/' + page;
			}
			
			rd = request.getRequestDispatcher(targetUrl);
			ImportResponseWrapper irw = new ImportResponseWrapper(pageContext.getResponse(), pageContext.getOut());

			String previous_sp = sp;
			sp = targetUrl.substring(0, targetUrl.lastIndexOf('/'));
			request.setAttribute(SERVLET_PATH, sp);
			rd.include(request, irw);
			if (first == true) {
				request.removeAttribute(SERVLET_PATH);
			} else {
				request.setAttribute(SERVLET_PATH, previous_sp);
			}
		} catch (IOException ioe) {
		} catch (ServletException sex) {
		}

		// end of the page, remove not persistent params....
		for (int i = 0; i < attrs.size(); i++) {
			request.removeAttribute((String)attrs.get(i));
		}
		return EVAL_PAGE;
	}
}