serial/CustomSerializer.java

   1 package be.nikiroo.utils.serial;
   2
   3 import java.io.IOException;
   4 import java.io.InputStream;
   5 import java.io.OutputStream;
   6
   7 import be.nikiroo.utils.streams.BufferedInputStream;
   8 import be.nikiroo.utils.streams.ReplaceInputStream;
   9 import be.nikiroo.utils.streams.ReplaceOutputStream;
  10
  11 /**
  12  * A {@link CustomSerializer} supports and generates values in the form:
  13  * <ul>
  14  * <li><tt>custom^<i>TYPE</i>^<i>ENCODED_VALUE</i></tt></li>
  15  * </ul>
  16  * <p>
  17  * In this scheme, the values are:
  18  * <ul>
  19  * <li><tt>custom</tt>: a fixed keyword</li>
  20  * <li><tt>^</tt>: a fixed separator character (the
  21  * <tt><i>ENCODED_VALUE</i></tt> can still use it inside its content, though</li>
  22  * <li><tt><i>TYPE</i></tt>: the object type of this value</li>
  23  * <li><tt><i>ENCODED_VALUE</i></tt>: the custom encoded value</li>
  24  * </ul>
  25  * <p>
  26  * To create a new {@link CustomSerializer}, you are expected to implement the
  27  * abstract methods of this class. The rest should be taken care of bythe
  28  * system.
  29  *
  30  * @author niki
  31  */
  32 public abstract class CustomSerializer {
  33         /**
  34          * Generate the custom <tt><i>ENCODED_VALUE</i></tt> from this
  35          * <tt>value</tt>.
  36          * <p>
  37          * The <tt>value</tt> will always be of the supported type.
  38          *
  39          * @param out
  40          *            the {@link OutputStream} to write the value to
  41          * @param value
  42          *            the value to serialize
  43          *
  44          * @throws IOException
  45          *             in case of I/O error
  46          */
  47         protected abstract void toStream(OutputStream out, Object value)
  48                         throws IOException;
  49
  50         /**
  51          * Regenerate the value from the custom <tt><i>ENCODED_VALUE</i></tt>.
  52          * <p>
  53          * The value in the {@link InputStream} <tt>in</tt> will always be of the
  54          * supported type.
  55          *
  56          * @param in
  57          *            the {@link InputStream} containing the
  58          *            <tt><i>ENCODED_VALUE</i></tt>
  59          *
  60          * @return the regenerated object
  61          *
  62          * @throws IOException
  63          *             in case of I/O error
  64          */
  65         protected abstract Object fromStream(InputStream in) throws IOException;
  66
  67         /**
  68          * Return the supported type name.
  69          * <p>
  70          * It <b>must</b> be the name returned by {@link Object#getClass()
  71          * #getCanonicalName()}.
  72          *
  73          * @return the supported class name
  74          */
  75         protected abstract String getType();
  76
  77         /**
  78          * Encode the object into the given {@link OutputStream}, i.e., generate the
  79          * <tt><i>ENCODED_VALUE</i></tt> part.
  80          * <p>
  81          * Use whatever scheme you wish, the system shall ensure that the content is
  82          * correctly encoded and that you will receive the same content at decode
  83          * time.
  84          *
  85          * @param out
  86          *            the builder to append to
  87          * @param value
  88          *            the object to encode
  89          *
  90          * @throws IOException
  91          *             in case of I/O error
  92          */
  93         public void encode(OutputStream out, Object value) throws IOException {
  94                 ReplaceOutputStream replace = new ReplaceOutputStream(out, //
  95                                 new String[] { "\\", "\n" }, //
  96                                 new String[] { "\\\\", "\\n" });
  97
  98                 try {
  99                         SerialUtils.write(replace, "custom^");
 100                         SerialUtils.write(replace, getType());
 101                         SerialUtils.write(replace, "^");
 102                         toStream(replace, value);
 103                 } finally {
 104                         replace.close(false);
 105                 }
 106         }
 107
 108         /**
 109          * Decode the value back into the supported object type.
 110          * <p>
 111          * We do <b>not</b> expect the full content here but only:
 112          * <ul>
 113          * <li>ENCODED_VALUE
 114          * <li>
 115          * </ul>
 116          * That is, we do not expect the "<tt>custom</tt>^<tt><i>TYPE</i></tt>^"
 117          * part.
 118          *
 119          * @param in
 120          *            the encoded value
 121          *
 122          * @return the object
 123          *
 124          * @throws IOException
 125          *             in case of I/O error
 126          */
 127         public Object decode(InputStream in) throws IOException {
 128                 ReplaceInputStream replace = new ReplaceInputStream(in, //
 129                                 new String[] { "\\\\", "\\n" }, //
 130                                 new String[] { "\\", "\n" });
 131
 132                 try {
 133                         return fromStream(replace);
 134                 } finally {
 135                         replace.close(false);
 136                 }
 137         }
 138
 139         public static boolean isCustom(BufferedInputStream in) throws IOException {
 140                 return in.startsWith("custom^");
 141         }
 142
 143         public static String typeOf(String encodedValue) {
 144                 int pos1 = encodedValue.indexOf('^');
 145                 int pos2 = encodedValue.indexOf('^', pos1 + 1);
 146                 String type = encodedValue.substring(pos1 + 1, pos2);
 147
 148                 return type;
 149         }
 150 }