Eclipse Property Testers (Test expression) 的使用

Eclipse Resource Plugin里面很多值得一看的东西，其中一个就是Property Testers ，它在某些条件过滤的时候非常有用，先看一段jdt里面的使用

      <page            objectvalue="org.eclipse.jdt.core.javanature"/>     </adapt>                  </enabledWhen>      </page>

?这里的

org.eclipse.core.resources.projectNature

就是eclipse已经定义好的property。

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扩展点：org.eclipse.core.expressions.propertyTesters

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作用：用来给一个已知的类型添加属性测试支持，新添加的属性可以用于各种表达式条件判断。

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扩展语法：

<!ELEMENT propertyTester EMPTY><!ATTLIST propertyTester    id    CDATA #REQUIRED    type   CDATA #REQUIRED   namespace  CDATA #REQUIRED   properties CDATA #REQUIRED   class  CDATA #REQUIRED>

? 引用一下Eclipse自己的解释：

<extension point="org.eclipse.core.expressions.propertyTesters"> <propertyTester id="org.eclipse.core.expressions.bundlePropertyTester" type="org.eclipse.core.runtime.Platform" namespace="org.eclipse.core.runtime" properties="product,isBundleInstalled,bundleState" name="code">/******************************************************************************* * Copyright (c) 2006, 2008 IBM Corporation and others. * All rights reserved. This program and the accompanying materials * are made available under the terms of the Eclipse Public License v1.0 * which accompanies this distribution, and is available at * http://www.eclipse.org/legal/epl-v10.html * * Contributors: * IBM Corporation - initial API and implementation *******************************************************************************/package org.eclipse.core.internal.expressions.propertytester;import org.osgi.framework.Bundle;import org.eclipse.core.expressions.PropertyTester;import org.eclipse.core.runtime.IProduct;import org.eclipse.core.runtime.Platform;/** * A property tester for testing platform properties. Can test whether or * not a given bundle is installed in the running environment, as well as * the id of the currently active product. * <p> * For example:<br /> * <test property="org.eclipse.core.runtime.product" value="org.eclipse.sdk.ide"/> <br /> * <test property="org.eclipse.core.runtime.isBundleInstalled" args="org.eclipse.core.expressions"/> <br /> * <test property="org.eclipse.core.runtime.bundleState" args="org.eclipse.core.expressions" value="ACTIVE"/> * <p> */public class PlatformPropertyTester extends PropertyTester {private static final String PROPERTY_PRODUCT = "product"; //$NON-NLS-1$private static final String PROPERTY_IS_BUNDLE_INSTALLED = "isBundleInstalled"; //$NON-NLS-1$private static final String PROPERTY_BUNDLE_STATE = "bundleState"; //$NON-NLS-1$/* (non-Javadoc) * @see org.eclipse.core.expressions.IPropertyTester#test(java.lang.Object, java.lang.String, java.lang.Object[], java.lang.Object) */public boolean test(Object receiver, String property, Object[] args, Object expectedValue) {if (Platform.class.equals(receiver)) {if (PROPERTY_PRODUCT.equals(property)) {IProduct product= Platform.getProduct();if (product != null) {return product.getId().equals(expectedValue);}return false;} else if (PROPERTY_IS_BUNDLE_INSTALLED.equals(property) && args.length >= 1 && args[0] instanceof String) {return Platform.getBundle((String)args[0]) != null;} else if (PROPERTY_BUNDLE_STATE.equals(property)&& args.length >= 1 && args[0] instanceof String) {Bundle b = Platform.getBundle((String) args[0]);if (b != null) {return bundleState(b.getState(), expectedValue);}return false;}}return false;}private boolean bundleState(int bundleState, Object expectedValue) {if ("UNINSTALLED".equals(expectedValue)) { //$NON-NLS-1$return bundleState == Bundle.UNINSTALLED;}if ("INSTALLED".equals(expectedValue)) { //$NON-NLS-1$return bundleState == Bundle.INSTALLED;}if ("RESOLVED".equals(expectedValue)) { //$NON-NLS-1$return bundleState == Bundle.RESOLVED;}if ("STARTING".equals(expectedValue)) { //$NON-NLS-1$return bundleState == Bundle.STARTING;}if ("STOPPING".equals(expectedValue)) { //$NON-NLS-1$return bundleState == Bundle.STOPPING;}if ("ACTIVE".equals(expectedValue)) { //$NON-NLS-1$return bundleState == Bundle.ACTIVE;}return false;}}?

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