trunk/core/src/main/java/org/apache/struts2/components/Property.java

/*
 * $Id$
 *
 * Copyright 2006 The Apache Software Foundation.
 *
 * Licensed 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.struts2.components;

import java.io.IOException;
import java.io.Writer;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import com.opensymphony.xwork2.util.OgnlValueStack;
import com.opensymphony.xwork2.util.TextUtils;

/**
 * <!-- START SNIPPET: javadoc -->
 * 
 * Used to get the property of a <i>value</i>, which will default to the top of
 * the stack if none is specified.
 * 
 * <!-- END SNIPPET: javadoc -->
 * 
 * <p/>
 * 
 *
 * <!-- START SNIPPET: params -->
 * 
 * <ul>
 *      <li>default (String) - The default value to be used if <u>value</u> attribute is null</li>
 *      <li>escape (Boolean) - Escape HTML. Default to true</li>
 *      <li>value (Object) - value to be displayed</li>
 * </ul>
 * 
 * <!-- END SNIPPET: params -->
 *
 *
 * <pre>
 * <!-- START SNIPPET: example -->
 * 
 * <s:push value="myBean">
 *     <!-- Example 1: -->
 *     <s:property value="myBeanProperty" />
 *
 *     <!-- Example 2: -->TextUtils
 *     <s:property value="myBeanProperty" default="a default value" />
 * </s:push>
 * 
 * <!-- END SNIPPET: example -->
 * </pre>
 * 
 * <pre>
 * <!-- START SNIPPET: exampledescription -->
 * 
 * Example 1 prints the result of myBean's getMyBeanProperty() method.
 * Example 2 prints the result of myBean's getMyBeanProperty() method and if it is null, print 'a default value' instead.
 * 
 * <!-- END SNIPPET: exampledescription -->
 * </pre>
 * 
 * 
 * <pre>
 * <!-- START SNIPPET: i18nExample -->
 * 
 * &lt;s:property value="getText('some.key')" /&gt;
 * 
 * <!-- END SNIPPET: i18nExample -->
 * </pre>
 *
 * @s.tag name="property" tld-body-content="empty" tld-tag-class="org.apache.struts2.views.jsp.PropertyTag"
 * description="Print out expression which evaluates against the stack"
 */
public class Property extends Component {
    private static final Log LOG = LogFactory.getLog(Property.class);

    public Property(OgnlValueStack stack) {
        super(stack);
    }

    private String defaultValue;
    private String value;
    private boolean escape = true;

    /**
     * The default value to be used if <u>value</u> attribute is null
     * @s.tagattribute required="false" type="String"
     */
    public void setDefault(String defaultValue) {
        this.defaultValue = defaultValue;
    }

    /**
     * Whether to escape HTML
     * @s.tagattribute required="false" type="Boolean" default="true"
     */
    public void setEscape(boolean escape) {
        this.escape = escape;
    }

    /**
     * value to be displayed
     * @s.tagattribute required="false" type="Object" default="&lt;top of stack&gt;"
     */
    public void setValue(String value) {
        this.value = value;
    }

    public boolean start(Writer writer) {
        boolean result = super.start(writer);

        String actualValue = null;

        if (value == null) {
            value = "top";
        }
        else if (altSyntax()) {
            // the same logic as with findValue(String)
            // if value start with %{ and end with }, just cut it off!
            if (value.startsWith("%{") && value.endsWith("}")) {
                value = value.substring(2, value.length() - 1);
            }
        }

        // exception: don't call findString(), since we don't want the
        //            expression parsed in this one case. it really
        //            doesn't make sense, in fact.
        actualValue = (String) getStack().findValue(value, String.class);

        try {
            if (actualValue != null) {
                writer.write(prepare(actualValue));
            } else if (defaultValue != null) {
                writer.write(prepare(defaultValue));
            }
        } catch (IOException e) {
            LOG.info("Could not print out value '" + value + "'", e);
        }

        return result;
    }

    private String prepare(String value) {
        if (escape) {
            return TextUtils.htmlEncode(value);
        } else {
            return value;
        }
    }
}