opendaylight/netconf/netconf-netty-util/src/main/java/org/opendaylight/controller/netconf/nettyutil/handler/ThreadLocalTransformers.java

   1 /*
   2  * Copyright (c) 2014 Cisco Systems, Inc. and others.  All rights reserved.
   3  *
   4  * This program and the accompanying materials are made available under the
   5  * terms of the Eclipse Public License v1.0 which accompanies this distribution,
   6  * and is available at http://www.eclipse.org/legal/epl-v10.html
   7  */
   8 package org.opendaylight.controller.netconf.nettyutil.handler;
   9
  10 import javax.xml.transform.OutputKeys;
  11 import javax.xml.transform.Transformer;
  12 import javax.xml.transform.TransformerConfigurationException;
  13 import javax.xml.transform.TransformerFactory;
  14 import javax.xml.transform.TransformerFactoryConfigurationError;
  15
  16 /**
  17  * Utility class for cached thread-local transformers. This class exists mostly for use by handlers.
  18  */
  19 final class ThreadLocalTransformers {
  20     private static final TransformerFactory FACTORY = TransformerFactory.newInstance();
  21
  22     private static final ThreadLocal<Transformer> DEFAULT_TRANSFORMER = new ThreadLocal<Transformer>() {
  23         @Override
  24         protected Transformer initialValue() {
  25             try {
  26                 return FACTORY.newTransformer();
  27             } catch (TransformerConfigurationException | TransformerFactoryConfigurationError e) {
  28                 throw new IllegalStateException("Unexpected error while instantiating a Transformer", e);
  29             }
  30         };
  31
  32         @Override
  33         public void set(final Transformer value) {
  34             throw new UnsupportedOperationException();
  35         };
  36     };
  37
  38     private static final ThreadLocal<Transformer> PRETTY_TRANSFORMER = new ThreadLocal<Transformer>() {
  39         @Override
  40         protected Transformer initialValue() {
  41             final Transformer ret;
  42
  43             try {
  44                 ret = FACTORY.newTransformer();
  45             } catch (TransformerConfigurationException | TransformerFactoryConfigurationError e) {
  46                 throw new IllegalStateException("Unexpected error while instantiating a Transformer", e);
  47             }
  48
  49             ret.setOutputProperty(OutputKeys.INDENT, "yes");
  50             ret.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "yes");
  51             return ret;
  52         };
  53
  54         @Override
  55         public void set(final Transformer value) {
  56             throw new UnsupportedOperationException();
  57         };
  58     };
  59
  60     private ThreadLocalTransformers() {
  61         throw new UnsupportedOperationException("Utility class");
  62     }
  63
  64     /**
  65      * Get the transformer with default configuration.
  66      *
  67      * @return A transformer with default configuration based on the default implementation.
  68      */
  69     public static Transformer getDefaultTransformer() {
  70         return DEFAULT_TRANSFORMER.get();
  71     }
  72
  73     /**
  74      * Get the transformer with default configuration, but with automatic indentation
  75      * and the XML declaration removed.
  76      *
  77      * @return A transformer with human-friendly configuration.
  78      */
  79     public static Transformer getPrettyTransformer() {
  80         return PRETTY_TRANSFORMER.get();
  81     }
  82 }