New filter reader to access straight-forward 'constants' defined in a class file.

This can be used to load class constants as Ant properties.

External Dependency on: BCEL

PR: 6591


git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@271660 13f79535-47bb-0310-9956-ffa450edef68

proposal/sandbox/filterreaders/src/main/org/apache/tools/ant/filters/ClassConstants.java

@@ -0,0 +1,182 @@
+/*
+ *  The Apache Software License, Version 1.1
+ *
+ *  Copyright (c) 2002 The Apache Software Foundation.  All rights
+ *  reserved.
+ *
+ *  Redistribution and use in source and binary forms, with or without
+ *  modification, are permitted provided that the following conditions
+ *  are met:
+ *
+ *  1. Redistributions of source code must retain the above copyright
+ *  notice, this list of conditions and the following disclaimer.
+ *
+ *  2. Redistributions in binary form must reproduce the above copyright
+ *  notice, this list of conditions and the following disclaimer in
+ *  the documentation and/or other materials provided with the
+ *  distribution.
+ *
+ *  3. The end-user documentation included with the redistribution, if
+ *  any, must include the following acknowlegement:
+ *  "This product includes software developed by the
+ *  Apache Software Foundation (http://www.apache.org/)."
+ *  Alternately, this acknowlegement may appear in the software itself,
+ *  if and wherever such third-party acknowlegements normally appear.
+ *
+ *  4. The names "The Jakarta Project", "Ant", and "Apache Software
+ *  Foundation" must not be used to endorse or promote products derived
+ *  from this software without prior written permission. For written
+ *  permission, please contact apache@apache.org.
+ *
+ *  5. Products derived from this software may not be called "Apache"
+ *  nor may "Apache" appear in their names without prior written
+ *  permission of the Apache Group.
+ *
+ *  THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
+ *  WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ *  OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ *  DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
+ *  ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ *  SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ *  LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+ *  USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ *  ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ *  OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ *  OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ *  SUCH DAMAGE.
+ *  ====================================================================
+ *
+ *  This software consists of voluntary contributions made by many
+ *  individuals on behalf of the Apache Software Foundation.  For more
+ *  information on the Apache Software Foundation, please see
+ *  <http://www.apache.org/>.
+ */
+package org.apache.tools.ant.filters;
+
+import java.io.ByteArrayInputStream;
+import java.io.IOException;
+import java.io.Reader;
+
+import org.apache.tools.ant.Project;
+
+import org.apache.bcel.*;
+import org.apache.bcel.classfile.*;
+
+/**
+ * Assemble the constants declared in a file in
+ * key1=value1(line separator)key2=value2
+ * format
+ *
+ * Notes:
+ * =====
+ * 1. This filter uses the BCEL external toolkit.
+ * 2. This assembles only those constants that are not created
+ *    using the syntax new whatever().
+ * 3. This assembles constants declared using the basic datatypes
+ *    and String only.
+ * 4. The access modifiers of the declared constants do not matter.
+ *
+ * Example:
+ * =======
+ *
+ * &lt;classconstants/&gt;
+ *
+ * Or:
+ *
+ * &lt;filterreader classname=&quot;org.apache.tools.ant.filters.ClassConstants&quot;/&gt;
+ *
+ * @author <a href="mailto:umagesh@apache.org">Magesh Umasankar</a>
+ */
+public final class ClassConstants
+    extends BaseFilterReader
+    implements ChainableReader
+{
+    /** System specific line separator. */
+    private static final String LS = System.getProperty("line.separator");
+
+    /** Data that must be read from, if not null. */
+    private String queuedData = null;
+
+    /**
+     * This constructor is a dummy constructor and is
+     * not meant to be used by any class other than Ant's
+     * introspection mechanism. This will close the filter
+     * that is created making it useless for further operations.
+     */
+    public ClassConstants() {
+        super();
+    }
+
+    /**
+     * Create a new filtered reader.
+     *
+     * @param in  a Reader object providing the underlying stream.
+     */
+    public ClassConstants(final Reader in) {
+        super(in);
+    }
+
+    /**
+     * Read and assemble the constants declared in a class file.
+     */
+    public final int read() throws IOException {
+
+        int ch = -1;
+
+        if (queuedData != null && queuedData.length() == 0) {
+            queuedData = null;
+        }
+
+        if (queuedData != null) {
+            ch = queuedData.charAt(0);
+            queuedData = queuedData.substring(1);
+            if (queuedData.length() == 0) {
+                queuedData = null;
+            }
+        } else {
+            String clazz = readFully();
+            if (clazz == null) {
+                ch = -1;
+            } else {
+                byte[] bytes = clazz.getBytes();
+                StringBuffer sb = new StringBuffer();
+                ByteArrayInputStream bis = new ByteArrayInputStream(bytes);
+                ClassParser parser = new ClassParser(bis, "");
+                JavaClass javaClass = parser.parse();
+                Field[] fields = javaClass.getFields();
+                for (int i = 0; i < fields.length; i++) {
+                    Field field = fields[i];
+                    if (field != null) {
+                        ConstantValue cv = field.getConstantValue();
+                        if (cv != null) {
+                            String cvs = cv.toString();
+                            //Remove start and end quotes if field is a String
+                            if (cvs.startsWith("\"") && cvs.endsWith("\"")) {
+                                cvs = cvs.substring(1, cvs.length() - 1);
+                            }
+                            sb.append(field.getName());
+                            sb.append('=');
+                            sb.append(cvs);
+                            sb.append(LS);
+                        }
+                    }
+                }
+
+                if (sb.length() > 0) {
+                    queuedData = sb.toString();
+                    return read();
+                }
+            }
+        }
+        return ch;
+    }
+
+    /**
+     * Create a new ClassConstants using the passed in
+     * Reader for instantiation.
+     */
+    public final Reader chain(final Reader rdr) {
+        ClassConstants newFilter = new ClassConstants(rdr);
+        return newFilter;
+    }
+}

proposal/sandbox/filterreaders/src/main/org/apache/tools/ant/types/FilterChain.java

@@ -55,6 +55,7 @@ package org.apache.tools.ant.types;
 
 import java.util.Vector;
 
+import org.apache.tools.ant.filters.ClassConstants;
 import org.apache.tools.ant.filters.ExpandProperties;
 import org.apache.tools.ant.filters.HeadFilter;
 import org.apache.tools.ant.filters.LineContains;
@@ -84,6 +85,10 @@ public final class FilterChain {
         return filterReaders;
     }
 
+    public final void addClassConstants(final ClassConstants classConstants) {
+        filterReaders.addElement(classConstants);
+    }
+
     public final void addExpandProperties(final ExpandProperties expandProperties) {
         filterReaders.addElement(expandProperties);
     }