Struts example source code file (IteratorGeneratorTag.java)

This example Struts source code file (IteratorGeneratorTag.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 - Struts tags/keywords

converter, default_separator, deprecated, http, iteratorgenerator, iteratorgeneratortag, jspexception, object, object, servlet, string, string, strutstagattribute, strutstagattribute, the, the

The Struts IteratorGeneratorTag.java source code

/*
 * $Id: IteratorGeneratorTag.java 651946 2008-04-27 13:41:38Z apetrelli $
 *
 * 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.struts2.views.jsp.iterator;

import javax.servlet.jsp.JspException;

import org.apache.struts2.util.IteratorGenerator;
import org.apache.struts2.util.IteratorGenerator.Converter;
import org.apache.struts2.views.annotations.StrutsTag;
import org.apache.struts2.views.annotations.StrutsTagAttribute;
import org.apache.struts2.views.jsp.StrutsBodyTagSupport;

import com.opensymphony.xwork2.util.logging.Logger;
import com.opensymphony.xwork2.util.logging.LoggerFactory;


/**
 * <!-- START SNIPPET: javadoc -->
 * <b>NOTE: JSP-TAG
 *
 * <p>Generate an iterator based on the val attribute supplied.

 *
 * <b>NOTE: The generated iterator will ALWAYS be pushed into the top of the stack, and poped
 * at the end of the tag.
 * <!-- END SNIPPET: javadoc -->
 *
 * <!-- START SNIPPET: params -->
 * <ul>
 *      <li>val* (Object) - the source to be parsed into an iterator 
 *      <li>count (Object) - the max number (Integer, Float, Double, Long, String) entries to be in the iterator
 *      <li>separator (String) - the separator to be used in separating the val into entries of the iterator
 *      <li>var (String) - the name to store the resultant iterator into page context, if such name is supplied
 *      <li>converter (Object) - the converter (must extends off IteratorGenerator.Converter interface) to convert the String entry parsed from val into an object
 * </ul>
 * <!-- END SNIPPET: params -->
 *
 *
 * <!-- START SNIPPET: example -->
 * Example One:
 * <pre>
 * Generate a simple iterator
 * <s:generator val="%{'aaa,bbb,ccc,ddd,eee'}">
 *  <s:iterator>
 *      <s:property /><br/>
 *  </s:iterator>
 * </s:generator>
 * </pre>
 * This generates an iterator and print it out using the iterator tag.
 *
 * Example Two:
 * <pre>
 * Generate an iterator with count attribute
 * <s:generator val="%{'aaa,bbb,ccc,ddd,eee'}" count="3">
 *  <s:iterator>
 *      <s:property /><br/>
 *  </s:iterator>
 * </s:generator>
 * </pre>
 * This generates an iterator, but only 3 entries will be available in the iterator
 * generated, namely aaa, bbb and ccc respectively because count attribute is set to 3
 *
 * Example Three:
 * <pre>
 * Generate an iterator with var attribute
 * <s:generator val="%{'aaa,bbb,ccc,ddd,eee'}" count="4" separator="," var="myAtt" />
 * <%
 *  Iterator i = (Iterator) pageContext.getAttribute("myAtt");
 *  while(i.hasNext()) {
 *      String s = (String) i.next(); %>
 *      <%=s%> <br/>
 * <%    }
 * %>
 * </pre>
 * This generates an iterator and put it in the PageContext under the key as specified
 * by the var attribute.
 *
 *
 * Example Four:
 * <pre>
 * Generate an iterator with comparator attribute
 * <s:generator val="%{'aaa,bbb,ccc,ddd,eee'}" converter="%{myConverter}">
 *  <s:iterator>
 *      <s:property /><br/>
 *  </s:iterator>
 * </s:generator>
 *
 *
 * public class GeneratorTagAction extends ActionSupport {
 *
 *   ....
 *
 *   public Converter getMyConverter() {
 *      return new Converter() {
 *          public Object convert(String value) throws Exception {
 *              return "converter-"+value;
 *          }
 *      };
 *   }
 *
 *   ...
 *
 * }
 * </pre>
 * This will generate an iterator with each entries decided by the converter supplied. With
 * this converter, it simply add "converter-" to each entries.
 * <!-- END SNIPPET: example -->
 *
 * @see org.apache.struts2.util.IteratorGenerator
 */
@StrutsTag(name="generator", tldTagClass="org.apache.struts2.views.jsp.iterator.IteratorGeneratorTag",
        description="Generate an iterator for a iterable source.")
public class IteratorGeneratorTag extends StrutsBodyTagSupport {

    private static final long serialVersionUID = 2968037295463973936L;

    public static final String DEFAULT_SEPARATOR = ",";

    private static final Logger LOG = LoggerFactory.getLogger(IteratorGeneratorTag.class);

    String countAttr;
    String separatorAttr;
    String valueAttr;
    String converterAttr;
    String var;
    IteratorGenerator iteratorGenerator = null;

    @StrutsTagAttribute(type="Integer",description="The max number entries to be in the iterator")
    public void setCount(String count) {
        countAttr = count;
    }

    /**
     * @s.tagattribute required="true" type="String"
     * description="the separator to be used in separating the <i>val into entries of the iterator"
     */
    @StrutsTagAttribute(required=true, description="The separator to be used in separating the <i>val into entries of the iterator")
    public void setSeparator(String separator) {
        separatorAttr = separator;
    }

    /**
     * @s.tagattribute required="true"
     * description="the source to be parsed into an iterator"
     */
    @StrutsTagAttribute(required=true, description="The source to be parsed into an iterator")
    public void setVal(String val) {
        valueAttr = val;
    }

    @StrutsTagAttribute(type="org.apache.struts2.util.IteratorGenerator.Converter",
            description="The converter to convert the String entry parsed from <i>val into an object")
    public void setConverter(String aConverter) {
        converterAttr = aConverter;
    }

    @StrutsTagAttribute(description="Deprecated. Use 'var' instead")
    public void setId(String string) {
        setVar(string);
    }

    @StrutsTagAttribute(description="The name to store the resultant iterator into page context, if such name is supplied")
    public void setVar(String var) {
        this.var = var;
    }

    public int doStartTag() throws JspException {

        // value
        Object value = findValue(valueAttr);

        // separator
        String separator = DEFAULT_SEPARATOR;
        if (separatorAttr != null && separatorAttr.length() > 0) {
            separator = findString(separatorAttr);
        }

        // TODO: maybe this could be put into an Util class, or there is already one?
        // count
        int count = 0;
        if (countAttr != null && countAttr.length() > 0) {
            Object countObj = findValue(countAttr);
            if (countObj instanceof Number) {
                count = ((Number)countObj).intValue();
            }
            else if (countObj instanceof String) {
                try {
                    count = Integer.parseInt((String)countObj);
                }
                catch(NumberFormatException e) {
                    LOG.warn("unable to convert count attribute ["+countObj+"] to number, ignore count attribute", e);
                }
            }
        }

        // converter
        Converter converter = null;
        if (converterAttr != null && converterAttr.length() > 0) {
            converter = (Converter) findValue(converterAttr);
        }


        iteratorGenerator = new IteratorGenerator();
        iteratorGenerator.setValues(value);
        iteratorGenerator.setCount(count);
        iteratorGenerator.setSeparator(separator);
        iteratorGenerator.setConverter(converter);

        iteratorGenerator.execute();

        // Push resulting iterator on stack and put into
        // stack context if we have a "var" specified.
        getStack().push(iteratorGenerator);
        if (var != null && var.length() > 0) {
            getStack().getContext().put(var, iteratorGenerator);
        }

        return EVAL_BODY_INCLUDE;
    }

    public int doEndTag() throws JspException {
        // pop resulting iterator from stack at end tag
        getStack().pop();
        iteratorGenerator = null; // clean up

        return EVAL_PAGE;
    }
}