propertyvariableinterpolator.java

来自「Wicket一个开发Java Web应用程序框架。它使得开发web应用程序变得容」· Java 代码 · 共 90 行

/*
 * 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.util.string.interpolator;

import org.apache.wicket.util.lang.PropertyResolver;

/**
 * Interpolates values into <code>String</code>s that are produced by interpreting property
 * expressions against a beans model.
 * <p>
 * The <code>interpolate(String string, Object model)</code> method takes a string such as "<code>My name is ${name}</code>"
 * and a beans model such as a <code>Person</code>, and reflects on the object using any property
 * expressions found inside <code>${}</code> markers in the <code>String</code>. In this case,
 * if the <code>Person</code> model has a <code>getName()</code> method. The results of calling
 * that method would be substituted for <code>${name}</code>. If <code>getName()</code>
 * returned <code>"Jonathan"</code>, then <code>interpolate()</code> would return
 * <code>"My name is Jonathan"</code>.
 * 
 * @author Jonathan Locke
 * @since 1.2.6
 */
public final class PropertyVariableInterpolator extends VariableInterpolator
{
	/** The model to introspect on */
	private final Object model;

	/**
	 * Private constructor to force use of static interpolate method.
	 * 
	 * @param string
	 *            a <code>String</code> to interpolate into
	 * @param model
	 *            the model to apply property expressions to
	 */
	private PropertyVariableInterpolator(final String string, final Object model)
	{
		super(string);
		this.model = model;
	}

	/**
	 * Interpolates the given <code>String</code>, substituting values for property expressions.
	 * 
	 * @param string
	 *            a <code>String</code> containing property expressions like <code>${xyz}</code>
	 * @param object
	 *            the <code>Object</code> to reflect on
	 * @return the interpolated <code>String</code>
	 */
	public static String interpolate(final String string, final Object object)
	{
		// If there's any reason to go to the expense of property expressions
		if (string.indexOf("${") != -1)
		{
			// Do property expression interpolation
			return new PropertyVariableInterpolator(string, object).toString();
		}

		// Return simple string
		return string;
	}

	/**
	 * Retrieves a value for a variable name during interpolation.
	 * 
	 * @param variableName
	 *            the variable name
	 * @return the value
	 */
	protected String getValue(final String variableName)
	{
		Object value = PropertyResolver.getValue(variableName, model);
		return (value != null) ? value.toString() : null;
	}
}