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Struts example source code file (ForEach.java)

This example Struts source code file (ForEach.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

byte, collection, collection, enumeration, float, foreach, iterator, iterator, map, object, object, string, string, tagplugin

The Struts ForEach.java source code

/*
 * 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.jasper.tagplugins.jstl.core;

import org.apache.struts2.jasper.compiler.tagplugin.*;

public final class ForEach implements TagPlugin {
    
    private boolean hasVar, hasBegin, hasEnd, hasStep;
    
    public void doTag(TagPluginContext ctxt) {
        
        String index = null;
        
        boolean hasVarStatus = ctxt.isAttributeSpecified("varStatus");
        if (hasVarStatus) {
            ctxt.dontUseTagPlugin();
            return;
        }
        
        hasVar = ctxt.isAttributeSpecified("var");
        hasBegin = ctxt.isAttributeSpecified("begin");
        hasEnd = ctxt.isAttributeSpecified("end");
        hasStep = ctxt.isAttributeSpecified("step");
        
        boolean hasItems = ctxt.isAttributeSpecified("items");
        if (hasItems) {
            doCollection(ctxt);
            return;
        }
        
        // We must have a begin and end attributes
        index = ctxt.getTemporaryVariableName();
        ctxt.generateJavaSource("for (int " + index + " = ");
        ctxt.generateAttribute("begin");
        ctxt.generateJavaSource("; " + index + " <= ");
        ctxt.generateAttribute("end");
        if (hasStep) {
            ctxt.generateJavaSource("; " + index + "+=");
            ctxt.generateAttribute("step");
            ctxt.generateJavaSource(") {");
        }
        else {
            ctxt.generateJavaSource("; " + index + "++) {");
        }
        
        // If var is specified and the body contains an EL, then sycn
        // the var attribute
        if (hasVar /* && ctxt.hasEL() */) {
            ctxt.generateJavaSource("_jspx_page_context.setAttribute(");
            ctxt.generateAttribute("var");
            ctxt.generateJavaSource(", String.valueOf(" + index + "));");
        }
        ctxt.generateBody();
        ctxt.generateJavaSource("}");
    }
    
    /**
     * Generate codes for Collections
     * The pseudo code is:
     */
    private void doCollection(TagPluginContext ctxt) {
        
        ctxt.generateImport("java.util.*");
        generateIterators(ctxt);
        
        String itemsV = ctxt.getTemporaryVariableName();
        ctxt.generateJavaSource("Object " + itemsV + "= ");
        ctxt.generateAttribute("items");
        ctxt.generateJavaSource(";");
        
        String indexV=null, beginV=null, endV=null, stepV=null;
        if (hasBegin) {
            beginV = ctxt.getTemporaryVariableName();
            ctxt.generateJavaSource("int " + beginV + " = ");
            ctxt.generateAttribute("begin");
            ctxt.generateJavaSource(";");
        }
        if (hasEnd) {
            indexV = ctxt.getTemporaryVariableName();
            ctxt.generateJavaSource("int " + indexV + " = 0;");
            endV = ctxt.getTemporaryVariableName();
            ctxt.generateJavaSource("int " + endV + " = ");
            ctxt.generateAttribute("end");
            ctxt.generateJavaSource(";");
        }
        if (hasStep) {
            stepV = ctxt.getTemporaryVariableName();
            ctxt.generateJavaSource("int " + stepV + " = ");
            ctxt.generateAttribute("step");
            ctxt.generateJavaSource(";");
        }
        
        String iterV = ctxt.getTemporaryVariableName();
        ctxt.generateJavaSource("Iterator " + iterV + " = null;");
        // Object[]
        ctxt.generateJavaSource("if (" + itemsV + " instanceof Object[])");
        ctxt.generateJavaSource(iterV + "=toIterator((Object[])" + itemsV + ");");
        // boolean[]
        ctxt.generateJavaSource("else if (" + itemsV + " instanceof boolean[])");
        ctxt.generateJavaSource(iterV + "=toIterator((boolean[])" + itemsV + ");");
        // byte[]
        ctxt.generateJavaSource("else if (" + itemsV + " instanceof byte[])");
        ctxt.generateJavaSource(iterV + "=toIterator((byte[])" + itemsV + ");");
        // char[]
        ctxt.generateJavaSource("else if (" + itemsV + " instanceof char[])");
        ctxt.generateJavaSource(iterV + "=toIterator((char[])" + itemsV + ");");
        // short[]
        ctxt.generateJavaSource("else if (" + itemsV + " instanceof short[])");
        ctxt.generateJavaSource(iterV + "=toIterator((short[])" + itemsV + ");");
        // int[]
        ctxt.generateJavaSource("else if (" + itemsV + " instanceof int[])");
        ctxt.generateJavaSource(iterV + "=toIterator((int[])" + itemsV + ");");
        // long[]
        ctxt.generateJavaSource("else if (" + itemsV + " instanceof long[])");
        ctxt.generateJavaSource(iterV + "=toIterator((long[])" + itemsV + ");");
        // float[]
        ctxt.generateJavaSource("else if (" + itemsV + " instanceof float[])");
        ctxt.generateJavaSource(iterV + "=toIterator((float[])" + itemsV + ");");
        // double[]
        ctxt.generateJavaSource("else if (" + itemsV + " instanceof double[])");
        ctxt.generateJavaSource(iterV + "=toIterator((double[])" + itemsV + ");");
        
        // Collection
        ctxt.generateJavaSource("else if (" + itemsV + " instanceof Collection)");
        ctxt.generateJavaSource(iterV + "=((Collection)" + itemsV + ").iterator();");
        
        // Iterator
        ctxt.generateJavaSource("else if (" + itemsV + " instanceof Iterator)");
        ctxt.generateJavaSource(iterV + "=(Iterator)" + itemsV + ";");
        
        // Enumeration
        ctxt.generateJavaSource("else if (" + itemsV + " instanceof Enumeration)");
        ctxt.generateJavaSource(iterV + "=toIterator((Enumeration)" + itemsV + ");");
        
        // Map
        ctxt.generateJavaSource("else if (" + itemsV + " instanceof Map)");
        ctxt.generateJavaSource(iterV + "=((Map)" + itemsV + ").entrySet().iterator();");
        
        if (hasBegin) {
            String tV = ctxt.getTemporaryVariableName();
            ctxt.generateJavaSource("for (int " + tV + "=" + beginV + ";" +
                    tV + ">0 && " + iterV + ".hasNext(); " +
                    tV + "--)");
            ctxt.generateJavaSource(iterV + ".next();");
        }
        
        ctxt.generateJavaSource("while (" + iterV + ".hasNext()){");
        if (hasVar) {
            ctxt.generateJavaSource("_jspx_page_context.setAttribute(");
            ctxt.generateAttribute("var");
            ctxt.generateJavaSource(", " + iterV + ".next());");
        }
        
        ctxt.generateBody();
        
        if (hasStep) {
            String tV = ctxt.getTemporaryVariableName();
            ctxt.generateJavaSource("for (int " + tV + "=" + stepV + "-1;" +
                    tV + ">0 && " + iterV + ".hasNext(); " +
                    tV + "--)");
            ctxt.generateJavaSource(iterV + ".next();");
        }
        if (hasEnd) {
            if (hasStep) {
                ctxt.generateJavaSource(indexV + "+=" + stepV + ";");
            }
            else {
                ctxt.generateJavaSource(indexV + "++;");
            }
            if (hasBegin) {
                ctxt.generateJavaSource("if(" + beginV + "+" + indexV +
                        ">"+ endV + ")");
            }
            else {
                ctxt.generateJavaSource("if(" + indexV + ">" + endV + ")");
            }
            ctxt.generateJavaSource("break;");
        }
        ctxt.generateJavaSource("}");	// while
    }
    
    /**
     * Generate iterators for data types supported in items
     */
    private void generateIterators(TagPluginContext ctxt) {
        
        // Object[]
        ctxt.generateDeclaration("ObjectArrayIterator", 
                "private Iterator toIterator(final Object[] a){\n" +
                "  return (new Iterator() {\n" +
                "    int index=0;\n" +
                "    public boolean hasNext() {\n" +
                "      return index < a.length;}\n" +
                "    public Object next() {\n" +
                "      return a[index++];}\n" +
                "    public void remove() {}\n" +
                "  });\n" +
                "}"
        );
        
        // boolean[]
        ctxt.generateDeclaration("booleanArrayIterator", 
                "private Iterator toIterator(final boolean[] a){\n" +
                "  return (new Iterator() {\n" +
                "    int index=0;\n" +
                "    public boolean hasNext() {\n" +
                "      return index < a.length;}\n" +
                "    public Object next() {\n" +
                "      return new Boolean(a[index++]);}\n" +
                "    public void remove() {}\n" +
                "  });\n" +
                "}"
        );
        
        // byte[]
        ctxt.generateDeclaration("byteArrayIterator", 
                "private Iterator toIterator(final byte[] a){\n" +
                "  return (new Iterator() {\n" +
                "    int index=0;\n" +
                "    public boolean hasNext() {\n" +
                "      return index < a.length;}\n" +
                "    public Object next() {\n" +
                "      return new Byte(a[index++]);}\n" +
                "    public void remove() {}\n" +
                "  });\n" +
                "}"
        );
        
        // char[]
        ctxt.generateDeclaration("charArrayIterator", 
                "private Iterator toIterator(final char[] a){\n" +
                "  return (new Iterator() {\n" +
                "    int index=0;\n" +
                "    public boolean hasNext() {\n" +
                "      return index < a.length;}\n" +
                "    public Object next() {\n" +
                "      return new Character(a[index++]);}\n" +
                "    public void remove() {}\n" +
                "  });\n" +
                "}"
        );
        
        // short[]
        ctxt.generateDeclaration("shortArrayIterator", 
                "private Iterator toIterator(final short[] a){\n" +
                "  return (new Iterator() {\n" +
                "    int index=0;\n" +
                "    public boolean hasNext() {\n" +
                "      return index < a.length;}\n" +
                "    public Object next() {\n" +
                "      return new Short(a[index++]);}\n" +
                "    public void remove() {}\n" +
                "  });\n" +
                "}"
        );
        
        // int[]
        ctxt.generateDeclaration("intArrayIterator", 
                "private Iterator toIterator(final int[] a){\n" +
                "  return (new Iterator() {\n" +
                "    int index=0;\n" +
                "    public boolean hasNext() {\n" +
                "      return index < a.length;}\n" +
                "    public Object next() {\n" +
                "      return new Integer(a[index++]);}\n" +
                "    public void remove() {}\n" +
                "  });\n" +
                "}"
        );
        
        // long[]
        ctxt.generateDeclaration("longArrayIterator", 
                "private Iterator toIterator(final long[] a){\n" +
                "  return (new Iterator() {\n" +
                "    int index=0;\n" +
                "    public boolean hasNext() {\n" +
                "      return index < a.length;}\n" +
                "    public Object next() {\n" +
                "      return new Long(a[index++]);}\n" +
                "    public void remove() {}\n" +
                "  });\n" +
                "}"
        );
        
        // float[]
        ctxt.generateDeclaration("floatArrayIterator",
                "private Iterator toIterator(final float[] a){\n" +
                "  return (new Iterator() {\n" +
                "    int index=0;\n" +
                "    public boolean hasNext() {\n" +
                "      return index < a.length;}\n" +
                "    public Object next() {\n" +
                "      return new Float(a[index++]);}\n" +
                "    public void remove() {}\n" +
                "  });\n" +
                "}"
        );
        
        // double[]
        ctxt.generateDeclaration("doubleArrayIterator",
                "private Iterator toIterator(final double[] a){\n" +
                "  return (new Iterator() {\n" +
                "    int index=0;\n" +
                "    public boolean hasNext() {\n" +
                "      return index < a.length;}\n" +
                "    public Object next() {\n" +
                "      return new Double(a[index++]);}\n" +
                "    public void remove() {}\n" +
                "  });\n" +
                "}"
        );
        
        // Enumeration
        ctxt.generateDeclaration("enumIterator",
                "private Iterator toIterator(final Enumeration e){\n" +
                "  return (new Iterator() {\n" +
                "    public boolean hasNext() {\n" +
                "      return e.hasMoreElements();}\n" +
                "    public Object next() {\n" +
                "      return e.nextElement();}\n" +
                "    public void remove() {}\n" +
                "  });\n" +
                "}"
        );
        
    }
}

Other Struts examples (source code examples)

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