Spring Framework example source code file (OptionTag.java)

This example Spring Framework source code file (OptionTag.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Spring Framework tags/keywords

abstracthtmlelementbodytag, bindstatus, display_value_variable_name, http, jsp, jspexception, jspexception, object, object, optiontag, selected_attribute, servlet, string, string, tagwriter, value_variable_name, value_variable_name

The Spring Framework OptionTag.java source code

/*
 * Copyright 2002-2008 the original author or authors.
 *
 * 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.springframework.web.servlet.tags.form;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.BodyContent;
import javax.servlet.jsp.tagext.BodyTag;

import org.springframework.util.Assert;
import org.springframework.web.servlet.support.BindStatus;
import org.springframework.web.util.TagUtils;

/**
 * JSP tag for rendering an HTML '<code>option' tag.
 * 
 * <p>Must be used nested inside a {@link SelectTag}.
 * 
 * <p>Provides full support for databinding by marking an
 * '<code>option' as 'selected' if the {@link #setValue value}
 * matches the value bound to the out {@link SelectTag}.
 *
 * <p>The {@link #setValue value} property is required and corresponds to
 * the '<code>value' attribute of the rendered 'option'.
 *
 * <p>An optional {@link #setLabel label} property can be specified, the
 * value of which corresponds to inner text of the rendered
 * '<code>option' tag. If no {@link #setLabel label} is specified
 * then the {@link #setValue value} property will be used when rendering
 * the inner text.
 *
 * @author Rob Harrop
 * @author Juergen Hoeller
 * @since 2.0
 */
public class OptionTag extends AbstractHtmlElementBodyTag implements BodyTag {

	/**
	 * The name of the JSP variable used to expose the value for this tag.
	 */
	public static final String VALUE_VARIABLE_NAME = "value";

	/**
	 * The name of the JSP variable used to expose the display value for this tag.
	 */
	public static final String DISPLAY_VALUE_VARIABLE_NAME = "displayValue";

	/**
	 * The name of the '<code>selected' attribute.
	 */
	private static final String SELECTED_ATTRIBUTE = "selected";

	/**
	 * The name of the '<code>value' attribute.
	 */
	private static final String VALUE_ATTRIBUTE = VALUE_VARIABLE_NAME;
	
	/**
	 * The name of the '<code>disabled' attribute.
	 */
	private static final String DISABLED_ATTRIBUTE = "disabled";


	/**
	 * The 'value' attribute of the rendered HTML <code><option> tag.
	 */
	private Object value;

	/**
	 * The text body of the rendered HTML <code><option> tag.
	 */
	private String label;

	private Object oldValue;

	private Object oldDisplayValue;
	
	private String disabled;


	/**
	 * Set the 'value' attribute of the rendered HTML <code><option> tag.
	 * <p>May be a runtime expression.
	 */
	public void setValue(Object value) {
		this.value = value;
	}

	/**
	 * Get the 'value' attribute of the rendered HTML <code><option> tag.
	 */
	protected Object getValue() {
		return this.value;
	}
	
	/**
	 * Set the value of the '<code>disabled' attribute.
	 * <p>May be a runtime expression.
	 * @param disabled the value of the '<code>disabled' attribute
	 */
	public void setDisabled(String disabled) {
		this.disabled = disabled;
	}

	/**
	 * Get the value of the '<code>disabled' attribute.
	 */
	protected String getDisabled() {
		return this.disabled;
	}
	
	/**
	 * Is the current HTML tag disabled?
	 * @return <code>true if this tag is disabled 
	 */
	protected boolean isDisabled() {
		return "true".equals(getDisabled());
	}

	/**
	 * Set the text body of the rendered HTML <code><option> tag.
	 * <p>May be a runtime expression.
	 */
	public void setLabel(String label) {
		Assert.notNull(label, "'label' must not be null");
		this.label = label;
	}

	/**
	 * Get the text body of the rendered HTML <code><option> tag.
	 */
	protected String getLabel() {
		return this.label;
	}


	protected void renderDefaultContent(TagWriter tagWriter) throws JspException {
		Object value = this.pageContext.getAttribute(VALUE_VARIABLE_NAME);
		String label = getLabelValue(value);
		renderOption(value,  label, tagWriter);
	}

	protected void renderFromBodyContent(BodyContent bodyContent, TagWriter tagWriter) throws JspException {
		Object value = this.pageContext.getAttribute(VALUE_VARIABLE_NAME);
		String label = bodyContent.getString();
		renderOption(value, label, tagWriter);
	}

	/**
	 * Make sure we are under a '<code>select' tag before proceeding.
	 */
	protected void onWriteTagContent() {
		assertUnderSelectTag();
	}

	protected void exposeAttributes() throws JspException {
		Object value = resolveValue();
		this.oldValue = this.pageContext.getAttribute(VALUE_VARIABLE_NAME);
		this.pageContext.setAttribute(VALUE_VARIABLE_NAME, value);
		this.oldDisplayValue = this.pageContext.getAttribute(DISPLAY_VALUE_VARIABLE_NAME);
		this.pageContext.setAttribute(DISPLAY_VALUE_VARIABLE_NAME, getDisplayString(value, getBindStatus().getEditor()));
	}

	protected BindStatus getBindStatus() {
		return (BindStatus) this.pageContext.getAttribute(SelectTag.LIST_VALUE_PAGE_ATTRIBUTE);
	}

	protected void removeAttributes() {
		if (this.oldValue != null) {
			this.pageContext.setAttribute(VALUE_ATTRIBUTE, this.oldValue);
			this.oldValue = null;
		}
		else {
			this.pageContext.removeAttribute(VALUE_VARIABLE_NAME);
		}

		if (this.oldDisplayValue != null) {
			this.pageContext.setAttribute(DISPLAY_VALUE_VARIABLE_NAME, this.oldDisplayValue);
			this.oldDisplayValue = null;
		}
		else {
			this.pageContext.removeAttribute(DISPLAY_VALUE_VARIABLE_NAME);
		}
	}

	private void renderOption(Object value, String label, TagWriter tagWriter) throws JspException {
		tagWriter.startTag("option");
		writeOptionalAttribute(tagWriter, "id", resolveId());
		writeOptionalAttributes(tagWriter);
		String renderedValue = getDisplayString(value, getBindStatus().getEditor());
		tagWriter.writeAttribute(VALUE_ATTRIBUTE, renderedValue);
		if (isSelected(value)) {
			tagWriter.writeAttribute(SELECTED_ATTRIBUTE, SELECTED_ATTRIBUTE);
		}
		if (isDisabled()) {
			tagWriter.writeAttribute(DISABLED_ATTRIBUTE, "disabled");
		}
		tagWriter.appendValue(label);
		tagWriter.endTag();
	}

	protected String autogenerateId() throws JspException {
		return null;
	}

	/**
	 * Returns the value of the label for this '<code>option' element.
	 * If the {@link #setLabel label} property is set then the resolved value
	 * of that property is used, otherwise the value of the <code>resolvedValue
	 * argument is used.
	 */
	private String getLabelValue(Object resolvedValue) throws JspException {
		String label = getLabel();
		Object labelObj = (label == null ? resolvedValue : evaluate("label", label));
		return  getDisplayString(labelObj, getBindStatus().getEditor());
	}

	private void assertUnderSelectTag() {
		TagUtils.assertHasAncestorOfType(this, SelectTag.class, "option", "select");
	}

	private boolean isSelected(Object resolvedValue) {
		return SelectedValueComparator.isSelected(getBindStatus(), resolvedValue);
	}

	private Object resolveValue() throws JspException {
		return evaluate(VALUE_VARIABLE_NAME, getValue());
	}

}