自己写的SelectTag-优快云博客

本文介绍了一种在Java Web应用中快速实现下拉选择菜单的方法。通过自定义的SelectTag，开发者能够轻松创建带有默认值及onChange事件的下拉菜单，极大地简化了开发过程。

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如果你没有spring的tag或struct的tag,使用我这个做下拉选单,还是很方便的.


<iit:select name= "selectName" items="${selectList}" itemValue = "selectValue" itemLabel = "selectLabel" selectValue="${selectValue}"/>

一个select下拉选单,一行搞定.
可以带onchange事件,带默认值选定
自己觉得使用很方便.


import java.util.Collection;
import java.util.Iterator;
import java.util.Map;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.tagext.TagSupport;

import org.apache.commons.beanutils.BeanUtils;

public class SelectTag extends TagSupport {

	/**
	 * 
	 */
	private static final long serialVersionUID = -9049765299272180960L;

	/**
	 * The {@link Collection}, {@link Map} or array of objects used to generate
	 * the inner '<code>option</code>' tags.
	 */
	private Object items;

	/**
	 * The name of the property mapped to the '<code>value</code>' attribute
	 * of the '<code>option</code>' tag.
	 */
	private String itemValue;

	/**
	 * The name of the property mapped to the inner text of the '<code>option</code>'
	 * tag.
	 */
	private String itemLabel;
	private String selectValue;
	private String emptyValue;
	private String name;
	private String id;

	private String onchange;

	public void release() {
		items = null;
		itemValue = null;
		itemLabel = null;
		selectValue = null;
		emptyValue = null;
		name = null;
		id = null;
		onchange = null;
	}

	@SuppressWarnings("unchecked")
	public int doEndTag() throws JspException {
		JspWriter jspOut = pageContext.getOut();
		try {
			jspOut.append("<select id=\"" + getId() + "\" name=\"" + name + "\" " + getOnchange() + " >");
			jspOut.append("<option value=\"" + getEmptyValue() + "\">Please Select</option>");
			if (items != null) {
				Collection itemsList = (Collection) items;
				for (Iterator iterator = itemsList.iterator(); iterator.hasNext();) {
					Object obj = (Object) iterator.next();
					Object value = BeanUtils.getProperty(obj, itemValue);
					Object label = BeanUtils.getProperty(obj, itemLabel);
					if (value != null && value.equals(selectValue)) {
						jspOut.append("<option value=\"" + value + "\" selected = \"selected\">" + label + "</option>");
					} else {
						jspOut.append("<option value=\"" + value + "\">" + label + "</option>");
					}

				}
			}
			jspOut.append("</select>");
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			itemValue = null;
			itemLabel = null;
			selectValue = null;
			emptyValue = null;
			name = null;
			id = null;
			onchange = null;
		}

		return EVAL_PAGE;
	}

	public String getId() {
		if (id == null) {
			id = name;
		}
		return id;
	}

	public void setName(String name) {
		this.name = name;
	}

	public void setId(String id) {
		this.id = id;
	}

	public void setItems(Object items) {
		this.items = items;
	}

	public void setItemValue(String itemValue) {
		this.itemValue = itemValue;
	}

	public void setItemLabel(String itemLabel) {
		this.itemLabel = itemLabel;
	}

	public void setSelectValue(String selectValue) {
		this.selectValue = selectValue;
	}

	public void setEmptyValue(String emptyValue) {
		this.emptyValue = emptyValue;
	}

	public String getEmptyValue() {
		if (emptyValue == null) {
			emptyValue = "-1";
		}
		return emptyValue;
	}

	public void setOnchange(String onchange) {
		this.onchange = onchange;
	}

	public String getOnchange() {
		if (onchange == null) {
			return "";
		}
		return "onchange=\"" + onchange + "\"";

	}
}


           <tag>
		<name>select</name>
		<tagclass>com...SelectTag</tagclass>
		<bodycontent>empty</bodycontent>
		<attribute>
			<name>name</name>
			<required>true</required>
			<rtexprvalue>true</rtexprvalue>
		</attribute>
		<attribute>
			<name>id</name>
			<required>false</required>
			<rtexprvalue>true</rtexprvalue>
		</attribute>
		<attribute>
			<name>items</name>
			<required>true</required>
			<rtexprvalue>true</rtexprvalue>
		</attribute>
		<attribute>
			<name>itemValue</name>
			<required>true</required>
			<rtexprvalue>true</rtexprvalue>
		</attribute>
		<attribute>
			<name>itemLabel</name>
			<required>true</required>
			<rtexprvalue>true</rtexprvalue>
		</attribute>

		<attribute>
			<name>emptyValue</name>
			<required>false</required>
			<rtexprvalue>true</rtexprvalue>
		</attribute>

		<attribute>
			<name>selectValue</name>
			<required>false</required>
			<rtexprvalue>true</rtexprvalue>
		</attribute>

		<attribute>
			<name>onchange</name>
			<required>false</required>
			<rtexprvalue>true</rtexprvalue>
		</attribute>
	</tag>