Java/Reflection/Package

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Demonstrates how to get declaration information on a Class

   <source lang="java">

/* 

*     file: PackageInfoDemo.java
*  package: oreilly.hcj.reflection
*
* This software is granted under the terms of the Common Public License,
* CPL, which may be found at the following URL:
* http://www-124.ibm.ru/developerworks/oss/CPLv1.0.htm
*
* Copyright(c) 2003-2005 by the authors indicated in the @author tags.
* All Rights are Reserved by the various authors.
*
                    1. DO NOT EDIT ABOVE THIS LINE ########## */

import java.util.Collection; /** 

* Demonstrates how to get declaration information on a Class.
*
* @author 
* @version $Revision: 1.3 $
*/

public class PackageInfoDemo { 

 /** 
  * Demonstration Method.
  *
  * @param args Command line arguments.
  */
 public static void main(final String[] args) {
   System.out.println(Object.class.getPackage());
   System.out.println(Float.class.getPackage());
   System.out.println(Collection.class.getPackage());
   System.out.println(int.class.getPackage());
   System.out.println(String.class.getPackage());
 }

} /* ########## End of File ########## */ 


 </source>



Detect if a package is available

   <source lang="java">

public class Main{ 

 public static void  main(String args[]) {
   System.out.println(isAvailable("javax.swing.JComponent"));
 }
 public static boolean isAvailable(String className) {
   boolean isFound = false;
   try {
      Class.forName(className, false, null);
      isFound = true;
   }
   catch (ClassNotFoundException e) {
      isFound = false;
   }
   return isFound;
 }

} 


 </source>



Get all information about a package

   <source lang="java">

class PackageInfo { 

 public static void main(String[] args) {
   Package p = Package.getPackage("java.lang");
   System.out.println("Name = " + p.getName());
   System.out.println("Implementation title = " + p.getImplementationTitle());
   System.out.println("Implementation vendor = " + p.getImplementationVendor());
   System.out.println("Implementation version = " + p.getImplementationVersion());
   System.out.println("Specification title = " + p.getSpecificationTitle());
   System.out.println("Specification vendor = " + p.getSpecificationVendor());
   System.out.println("Specification version = " + p.getSpecificationVersion());
 }

} 


 </source>



Get full package name

   <source lang="java">

public class Main { 

 public static String getPackageName(Class c) {
   String fullyQualifiedName = c.getName();
   int lastDot = fullyQualifiedName.lastIndexOf(".");
   if (lastDot == -1) {
     return "";
   }
   return fullyQualifiedName.substring(0, lastDot);
 }
 public static void main(String[] args) {
   System.out.println(getPackageName(java.awt.Frame.class));
 }

} 


 </source>



Get package by name

   <source lang="java">

public class Main { 

 public static void main(String[] a) {
   Package p = Package.getPackage("java.lang");
   System.out.println("Name = " + p.getName());
   System.out.println("Implementation title = " + p.getImplementationTitle());
   System.out.println("Implementation vendor = " + p.getImplementationVendor());
   System.out.println("Implementation version = " + p.getImplementationVersion());
 }

} /*Name = java.lang Implementation title = Java Runtime Environment Implementation vendor = Sun Microsystems, Inc. Implementation version = 1.6.0_02 

*/
  
   
   
 </source>



Get package name of a class

   <source lang="java">

import java.util.Date; public class Main { 

 public static void main(String[] args) {
   Date date = new Date();
   Package pack = date.getClass().getPackage();
   String packageName = pack.getName();
   System.out.println("Package Name = " + packageName);
 }

} 


 </source>



Get Package Names From Dir

   <source lang="java">

/** 

* 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.
*/

import java.io.File; import java.util.List; public final class ReflectionUtil { 

 private static void getPackageNamesFromDir(File base, File dir, List<String> pkgs) {
   boolean foundClass = false;
   for (File file : dir.listFiles()) {
     if (file.isDirectory()) {
       getPackageNamesFromDir(base, file, pkgs);
     } else if (!foundClass && file.getName().endsWith(".class")) {
       foundClass = true;
       String pkg = "";
       file = dir;
       while (!file.equals(base)) {
         if (!"".equals(pkg)) {
           pkg = "." + pkg;
         }
         pkg = file.getName() + pkg;
         file = file.getParentFile();
       }
       if (!pkgs.contains(pkg)) {
         pkgs.add(pkg);
       }
     }
   }
 }
 private static String getPackageName(String clzName) {
   if (clzName.indexOf("/") == -1) {
     return null;
   }
   String packageName = clzName.substring(0, clzName.lastIndexOf("/"));
   return packageName.replace("/", ".");
 }

} 

 </source>



getPackage() returns null for a class in the unnamed package

   <source lang="java">

public class Main { 

 public static void main(String[] argv) throws Exception {
   Class cls = MyClass.class;
   Package pkg = cls.getPackage(); // null
 }

} class MyClass{} 


 </source>



getPackage() returns null for a primitive type or array

   <source lang="java">

public class Main { 

 public static void main(String[] argv) throws Exception {
   Package pkg = int.class.getPackage(); // null
   pkg = int[].class.getPackage(); // null
 }

} 


 </source>



Get the class name with or without the package

   <source lang="java">

public class Main { 

 public static String getClassName(Class c) {
   String className = c.getName();
   int firstChar;
   firstChar = className.lastIndexOf(".") + 1;
   if (firstChar > 0) {
     className = className.substring(firstChar);
   }
   return className;
 }

 public static void main(String[] args) {
   System.out.println(getClassName(java.awt.Frame.class));
 }

} 


 </source>



Getting the Package of a Class

   <source lang="java">

public class Main { 

 public static void main(String[] argv) throws Exception {
   Class cls = java.lang.String.class;
   Package pkg = cls.getPackage();
   String name = pkg.getName(); // java.lang
 }

} 


 </source>



Package Utils

   <source lang="java">

/** 

* 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.
*/

import java.util.ArrayList; import java.util.Arrays; import java.util.HashSet; import java.util.List; import java.util.Set; import java.util.StringTokenizer;

public final class PackageUtils { 

   private static final Set<String> KEYWORDS = new HashSet<String>(Arrays
       .asList(new String[] {"abstract", "boolean", "break", "byte", "case", "catch", "char", "class",
                             "const", "continue", "default", "do", "double", "else", "extends", "final",
                             "finally", "float", "for", "goto", "if", "implements", "import", "instanceof",
                             "int", "interface", "long", "native", "new", "package", "private", "protected",
                             "public", "return", "short", "static", "strictfp", "super", "switch",
                             "synchronized", "this", "throw", "throws", "transient", "try", "void",
                             "volatile", "while", "true", "false", "null", "assert", "enum"}));
   
   private PackageUtils() {
       
   }
   
   static String getPackageName(String className) {
       int pos = className.lastIndexOf(".");
       if (pos != -1) {
           return className.substring(0, pos);
       } else {
           return "";
       }
   }
   
   public static String getPackageName(Class<?> clazz) {
       String className = clazz.getName();
       if (className.startsWith("[L")) {
           className = className.substring(2);
       }
       return getPackageName(className);
   }
   
   public static String parsePackageName(String namespace, String defaultPackageName) {
       String packageName = (defaultPackageName != null && defaultPackageName.trim().length() > 0)
           ? defaultPackageName : null;
       if (packageName == null) {
           packageName = getPackageNameByNameSpaceURI(namespace);
       }
       return packageName;
   }
   
   public static String getPackageNameByNameSpaceURI(String nameSpaceURI) {
       int idx = nameSpaceURI.indexOf(":");
       String scheme = "";
       if (idx >= 0) {
           scheme = nameSpaceURI.substring(0, idx);
           if ("http".equalsIgnoreCase(scheme) || "urn".equalsIgnoreCase(scheme)) {
               nameSpaceURI = nameSpaceURI.substring(idx + 1);
           }
       }
       List<String> tokens = tokenize(nameSpaceURI, "/: ");
       if (tokens.size() == 0) {
           return null;
       }
       if (tokens.size() > 1) {
           String lastToken = tokens.get(tokens.size() - 1);
           idx = lastToken.lastIndexOf(".");
           if (idx > 0) {
               lastToken = lastToken.substring(0, idx);
               tokens.set(tokens.size() - 1, lastToken);
           }
       }
       String domain = tokens.get(0);
       idx = domain.indexOf(":");
       if (idx >= 0) {
           domain = domain.substring(0, idx);
       }
       List<String> r = reverse(tokenize(domain, "urn".equals(scheme) ? ".-" : "."));
       if ("www".equalsIgnoreCase(r.get(r.size() - 1))) {
           // remove leading www
           r.remove(r.size() - 1);
       }
       // replace the domain name with tokenized items
       tokens.addAll(1, r);
       tokens.remove(0);
       // iterate through the tokens and apply xml->java name algorithm
       for (int i = 0; i < tokens.size(); i++) {
           // get the token and remove illegal chars
           String token = tokens.get(i);
           token = removeIllegalIdentifierChars(token);
           // this will check for reserved keywords
           if (containsReservedKeywords(token)) {
               token = "_" + token;
           }
           tokens.set(i, token.toLowerCase());
       }
       // concat all the pieces and return it
       return combine(tokens, ".");
   }
   private static List<String> tokenize(String str, String sep) {
       StringTokenizer tokens = new StringTokenizer(str, sep);
       List<String> r = new ArrayList<String>();
       while (tokens.hasMoreTokens()) {
           r.add(tokens.nextToken());
       }
       return r;
   }
   private static <T> List<T> reverse(List<T> a) {
       List<T> r = new ArrayList<T>();
       for (int i = a.size() - 1; i >= 0; i--) {
           r.add(a.get(i));
       }
       return r;
   }
   private static String removeIllegalIdentifierChars(String token) {
       StringBuffer newToken = new StringBuffer();
       for (int i = 0; i < token.length(); i++) {
           char c = token.charAt(i);
           if (i == 0 && !Character.isJavaIdentifierStart(c)) {
               // prefix an "_" if the first char is illegal
               newToken.append("_" + c);
           } else if (!Character.isJavaIdentifierPart(c)) {
               // replace the char with an "_" if it is illegal
               newToken.append("_");
           } else {
               // add the legal char
               newToken.append(c);
           }
       }
       return newToken.toString();
   }
   private static String combine(List r, char sep) {
       StringBuilder buf = new StringBuilder(r.get(0).toString());
       for (int i = 1; i < r.size(); i++) {
           buf.append(sep);
           buf.append(r.get(i));
       }
       return buf.toString();
   }
   private static boolean containsReservedKeywords(String token) {
       return KEYWORDS.contains(token);
   }
   public static String getNamespace(String packageName) {
       if (packageName == null || packageName.length() == 0) {
           return null;
       }
       StringTokenizer tokenizer = new StringTokenizer(packageName, ".");
       String[] tokens;
       if (tokenizer.countTokens() == 0) {
           tokens = new String[0];
       } else {
           tokens = new String[tokenizer.countTokens()];
           for (int i = tokenizer.countTokens() - 1; i >= 0; i--) {
               tokens[i] = tokenizer.nextToken();
           }
       }
       StringBuffer namespace = new StringBuffer("http://");
       String dot = "";
       for (int i = 0; i < tokens.length; i++) {
           if (i == 1) {
               dot = ".";
           }
           namespace.append(dot + tokens[i]);
       }
       namespace.append("/");
       return namespace.toString();
   }

} 


 </source>



Show the Packages

   <source lang="java">

/* 

* Copyright (c) Ian F. Darwin, http://www.darwinsys.ru/, 1996-2002.
* All rights reserved. Software written by Ian F. Darwin and others.
* $Id: LICENSE,v 1.8 2004/02/09 03:33:38 ian Exp $
*
* 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.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS""
* AND ANY EXPRESS 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 AUTHOR OR 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.
* 
* Java, the Duke mascot, and all variants of Sun"s Java "steaming coffee
* cup" logo are trademarks of Sun Microsystems. Sun"s, and James Gosling"s,
* pioneering role in inventing and promulgating (and standardizing) the Java 
* language and environment is gratefully acknowledged.
* 
* The pioneering role of Dennis Ritchie and Bjarne Stroustrup, of AT&T, for
* inventing predecessor languages C and C++ is also gratefully acknowledged.
*/

/** 

* Show the Packages. Requires JDK1.2.
* @author Ian F. Darwin, http://www.darwinsys.ru/
* @version $Id: Packages.java,v 1.4 2004/02/09 03:33:51 ian Exp $
*/

public class Packages { 

 public static void main(String[] argv) {
   //+
   java.lang.Package[] all = java.lang.Package.getPackages();
   for (int i=0; i<all.length; i++)
     System.out.println(all[i]);
   //-
 }

} 



 </source>
Источник — «http://jexp.ru/index.php?title=Java/Reflection/Package&oldid=6089»