Java tutorial
/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You under the Apache License, Version 2.0 * (the "License"); you may not use this file except in compliance with * the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package org.apache.wicket.markup.html.link; import org.apache.wicket.Component; import org.apache.wicket.IGenericComponent; import org.apache.wicket.IRequestListener; import org.apache.wicket.Page; import org.apache.wicket.WicketRuntimeException; import org.apache.wicket.markup.ComponentTag; import org.apache.wicket.model.IModel; import org.apache.wicket.request.mapper.parameter.PageParameters; /** * Implementation of a hyperlink component. A link can be used with an anchor (<a href...) * element or any element that supports the onclick javascript event handler (such as buttons, td * elements, etc). When used with an anchor, a href attribute will be generated. When used with any * other element, an onclick javascript event handler attribute will be generated. * <p> * You can use a link like: * * <pre> * add(new Link("myLink") * { * public void onClick() * { * // do something here... * } * ); * </pre> * * and in your HTML file: * * <pre> * <a href="#" wicket:id="myLink">click here</a> * </pre> * * or: * * <pre> * <td wicket:id="myLink">my clickable column</td> * </pre> * * </p> * The following snippet shows how to pass a parameter from the Page creating the Page to the Page * responded by the Link. * * <pre> * add(new Link<MyObject>("link", listItem.getModel()) * { * public void onClick() * { * MyObject obj = getModelObject(); * setResponsePage(new MyPage(obj)); * } * </pre> * * @author Jonathan Locke * @author Eelco Hillenius * @param <T> * type of model object */ public abstract class Link<T> extends AbstractLink implements IRequestListener, IGenericComponent<T, Link<T>> { private static final long serialVersionUID = 1L; /** * An anchor (form 'http://server/app/etc#someAnchor') will be appended to the link so that * after this link executes, it will jump to the provided anchor component's position. The * provided anchor must either have the {@link Component#getOutputMarkupId()} flag true, or it * must be attached to a <a tag with a href attribute of more than one character starting * with '#' ('<a href="#someAnchor" ... '). */ private Component anchor; /** * True if link should automatically enable/disable based on current page; false by default. */ private boolean autoEnable = false; /** * The popup specification. If not-null, a javascript on-click event handler will be generated * that opens a new window using the popup properties. */ private PopupSettings popupSettings = null; /** * @see org.apache.wicket.Component#Component(String) */ public Link(final String id) { super(id); } /** * @param id * @param model * @see org.apache.wicket.Component#Component(String, IModel) */ public Link(final String id, IModel<T> model) { super(id, model); } /** * Gets any anchor component. * * @return Any anchor component to jump to, might be null */ public Component getAnchor() { return anchor; } /** * Gets whether link should automatically enable/disable based on current page. * * @return Whether this link should automatically enable/disable based on current page. */ public final boolean getAutoEnable() { return autoEnable; } /** * Gets the popup specification. If not-null, a javascript on-click event handler will be * generated that opens a new window using the popup properties. * * @return the popup specification. */ public final PopupSettings getPopupSettings() { return popupSettings; } /** * @see org.apache.wicket.Component#isEnabled() */ @Override public boolean isEnabled() { // If we're auto-enabling if (getAutoEnable()) { // the link is enabled if this link doesn't link to the current page return !linksTo(getPage()); } return super.isEnabled(); } /** * @see org.apache.wicket.Component#getStatelessHint() */ @Override protected boolean getStatelessHint() { return false; } /** * Called when a link is clicked. */ public abstract void onClick(); /** * THIS METHOD IS NOT PART OF THE WICKET API. DO NOT ATTEMPT TO OVERRIDE OR CALL IT. * * Called when a link is clicked. The implementation of this method is currently to simply call * onClick(), but this may be augmented in the future. */ @Override public void onRequest() { // Invoke subclass handler onClick(); } /** * Sets an anchor component. An anchor (form 'http://server/app/etc#someAnchor') will be * appended to the link so that after this link executes, it will jump to the provided anchor * component's position. The provided anchor must either have the * {@link Component#getOutputMarkupId()} flag true, or it must be attached to a <a tag with a * href attribute of more than one character starting with '#' ('<a href="#someAnchor" ... * '). * * @param anchor * The anchor * @return this */ public Link<T> setAnchor(Component anchor) { addStateChange(); this.anchor = anchor; return this; } /** * Sets whether this link should automatically enable/disable based on current page. * * @param autoEnable * whether this link should automatically enable/disable based on current page. * @return This */ public final Link<T> setAutoEnable(final boolean autoEnable) { this.autoEnable = autoEnable; return this; } /** * Sets the popup specification. If not-null, a javascript on-click event handler will be * generated that opens a new window using the popup properties. * * @param popupSettings * the popup specification. * @return This */ public final Link<T> setPopupSettings(final PopupSettings popupSettings) { this.popupSettings = popupSettings; return this; } /** * Appends any anchor to the url if the url is not null and the url does not already contain an * anchor (url.indexOf('#') != -1). This implementation looks whether an anchor component was * set, and if so, it will append the markup id of that component. That markup id is gotten by * either calling {@link Component#getMarkupId()} if {@link Component#getOutputMarkupId()} * returns true, or if the anchor component does not output it's id, this method will try to * retrieve the id from the markup directly. If neither is found, an * {@link WicketRuntimeException exception} is thrown. If no anchor component was set, but the * link component is attached to a <a element, this method will append what is in the href * attribute <i>if</i> there is one, starts with a '#' and has more than one character. * <p> * You can override this method, but it means that you have to take care of whatever is done * with any set anchor component yourself. You also have to manually append the '#' at the right * place. * </p> * * @param tag * The component tag * @param url * The url to start with * @return The url, possibly with an anchor appended */ protected CharSequence appendAnchor(final ComponentTag tag, CharSequence url) { if (url != null) { Component anchor = getAnchor(); if (anchor != null) { if (url.toString().indexOf('#') == -1) { String id; if (anchor.getOutputMarkupId()) { id = anchor.getMarkupId(); } else { id = anchor.getMarkupAttributes().getString("id"); } if (id != null) { url = url + "#" + anchor.getMarkupId(); } else { throw new WicketRuntimeException("an achor component was set on " + this + " but it neither has outputMarkupId set to true " + "nor has a id set explicitly"); } } } else { if (tag.getName().equalsIgnoreCase("a")) { if (url.toString().indexOf('#') == -1) { String href = tag.getAttributes().getString("href"); if (href != null && href.length() > 1 && href.charAt(0) == '#') { url = url + href; } } } } } return url; } /** * @param url * The url for the link * @return Any onClick JavaScript that should be used */ protected CharSequence getOnClickScript(final CharSequence url) { return null; } /** * Gets the url to use for this link. * * @return The URL that this link links to */ protected CharSequence getURL() { return urlForListener(new PageParameters()); } /** * Whether this link refers to the given page. * * @param page * A page * @return True if this link goes to the given page */ protected boolean linksTo(final Page page) { return false; } /** * Handles this link's tag. OVERRIDES MUST CALL SUPER. * * @param tag * the component tag * @see org.apache.wicket.Component#onComponentTag(ComponentTag) */ @Override protected void onComponentTag(final ComponentTag tag) { // Default handling for tag super.onComponentTag(tag); // If we're disabled if (isEnabledInHierarchy()) { // Set href to link to this link's linkClicked method CharSequence url = getURL(); // append any anchor url = appendAnchor(tag, url); // if the tag is an anchor proper if (tag.getName().equalsIgnoreCase("a") || tag.getName().equalsIgnoreCase("link") || tag.getName().equalsIgnoreCase("area")) { // generate the href attribute tag.put("href", url); // Add any popup script if (popupSettings != null) { // NOTE: don't encode to HTML as that is not valid // JavaScript tag.put("onclick", popupSettings.getPopupJavaScript()); } } else if (tag.getName().equalsIgnoreCase("script") || tag.getName().equalsIgnoreCase("style")) { tag.put("src", url); } else { // generate a popup script by asking popup settings for one if (popupSettings != null) { popupSettings.setTarget("'" + url + "'"); String popupScript = popupSettings.getPopupJavaScript(); tag.put("onclick", popupScript); } else { // or generate an onclick JS handler directly // in firefox when the element is quickly clicked 3 times a second request is // generated during page load. This check ensures that the click is ignored tag.put("onclick", "var win = this.ownerDocument.defaultView || this.ownerDocument.parentWindow; " + "if (win == window) { window.location.href='" + url + "'; } ;return false"); } } // If the subclass specified javascript, use that final CharSequence onClickJavaScript = getOnClickScript(url); if (onClickJavaScript != null) { tag.put("onclick", onClickJavaScript); } } else { disableLink(tag); } } }