refactor: simplify Encoding class (#765)

pgjdbc/src/main/java/org/postgresql/core/Encoding.java

@@ -12,13 +12,20 @@
import java.io.OutputStreamWriter;
import java.io.Reader;
import java.io.Writer;
import java.nio.charset.Charset;
import java.util.HashMap;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 * Representation of a particular character encoding.
 */
public class Encoding {
  private static final Encoding DEFAULT_ENCODING = new Encoding(null);

  private static final Logger LOGGER = Logger.getLogger(Encoding.class.getName());

  private static final Encoding DEFAULT_ENCODING = new Encoding();
  private static final Encoding UTF8_ENCODING = new Encoding("UTF-8");

  /*
   * Preferred JVM encodings for backend encodings.
@@ -28,10 +35,9 @@
  static {
    //Note: this list should match the set of supported server
    // encodings found in backend/util/mb/encnames.c
    encodings.put("SQL_ASCII", new String[]{"ASCII", "us-ascii"});
    encodings.put("SQL_ASCII", new String[]{"ASCII", "US-ASCII"});
    encodings.put("UNICODE", new String[]{"UTF-8", "UTF8"});
    encodings.put("UTF8",
        new String[]{"UTF-8", "UTF8"}); // 8.1's canonical name for UNICODE changed.
    encodings.put("UTF8", new String[]{"UTF-8", "UTF8"});
    encodings.put("LATIN1", new String[]{"ISO8859_1"});
    encodings.put("LATIN2", new String[]{"ISO8859_2"});
    encodings.put("LATIN3", new String[]{"ISO8859_3"});
@@ -73,9 +79,28 @@
  private final String encoding;
  private final boolean fastASCIINumbers;

  /**
   * Uses the default charset of the JVM.
   */
  private Encoding() {
    this(Charset.defaultCharset().name());
  }

  /**
   * Use the charset passed as parameter.
   *
   * @param encoding charset name to use
   */
  protected Encoding(String encoding) {
    if (encoding == null) {
      throw new NullPointerException("Null encoding charset not supported");
    }
    this.encoding = encoding;
    fastASCIINumbers = testAsciiNumbers();
    if (LOGGER.isLoggable(Level.FINEST)) {
      LOGGER.log(Level.FINEST, "Creating new Encoding {0} with fastASCIINumbers {1}",
          new Object[]{encoding, fastASCIINumbers});
    }
  }

  /**
@@ -96,14 +121,13 @@ public boolean hasAsciiNumbers() {
   * default JVM encoding if the specified encoding is unavailable.
   */
  public static Encoding getJVMEncoding(String jvmEncoding) {
    if (isAvailable(jvmEncoding)) {
      if (jvmEncoding.equals("UTF-8") || jvmEncoding.equals("UTF8")) {
        return new UTF8Encoding(jvmEncoding);
      } else {
        return new Encoding(jvmEncoding);
      }
    if ("UTF-8".equals(jvmEncoding)) {
      return new UTF8Encoding(jvmEncoding);
    }
    if (Charset.isSupported(jvmEncoding)) {
      return new Encoding(jvmEncoding);
    } else {
      return defaultEncoding();
      return DEFAULT_ENCODING;
    }
  }

@@ -115,27 +139,31 @@ public static Encoding getJVMEncoding(String jvmEncoding) {
   * default JVM encoding if the specified encoding is unavailable.
   */
  public static Encoding getDatabaseEncoding(String databaseEncoding) {
    if ("UTF8".equals(databaseEncoding)) {
      return UTF8_ENCODING;
    }
    // If the backend encoding is known and there is a suitable
    // encoding in the JVM we use that. Otherwise we fall back
    // to the default encoding of the JVM.

    String[] candidates = encodings.get(databaseEncoding);
    if (candidates != null) {
      for (String candidate : candidates) {
        if (isAvailable(candidate)) {
        LOGGER.log(Level.FINEST, "Search encoding candidate {0}", candidate);
        if (Charset.isSupported(candidate)) {
          return new Encoding(candidate);
        }
      }
    }

    // Try the encoding name directly -- maybe the charset has been
    // provided by the user.
    if (isAvailable(databaseEncoding)) {
    if (Charset.isSupported(databaseEncoding)) {
      return new Encoding(databaseEncoding);
    }

    // Fall back to default JVM encoding.
    return defaultEncoding();
    LOGGER.log(Level.FINEST, "{0} encoding not found, returning default encoding", databaseEncoding);
    return DEFAULT_ENCODING;
  }

  /**
@@ -144,7 +172,7 @@ public static Encoding getDatabaseEncoding(String databaseEncoding) {
   * @return the JVM encoding name used by this instance.
   */
  public String name() {
    return encoding;
    return Charset.isSupported(encoding) ? Charset.forName(encoding).name() : encoding;
  }

  /**
@@ -159,10 +187,6 @@ public String name() {
      return null;
    }

    if (encoding == null) {
      return s.getBytes();
    }

    return s.getBytes(encoding);
  }

@@ -177,10 +201,6 @@ public String name() {
   * @throws IOException if something goes wrong
   */
  public String decode(byte[] encodedString, int offset, int length) throws IOException {
    if (encoding == null) {
      return new String(encodedString, offset, length);
    }

    return new String(encodedString, offset, length, encoding);
  }

@@ -203,10 +223,6 @@ public String decode(byte[] encodedString) throws IOException {
   * @throws IOException if something goes wrong
   */
  public Reader getDecodingReader(InputStream in) throws IOException {
    if (encoding == null) {
      return new InputStreamReader(in);
    }

    return new InputStreamReader(in, encoding);
  }

@@ -218,10 +234,6 @@ public Reader getDecodingReader(InputStream in) throws IOException {
   * @throws IOException if something goes wrong
   */
  public Writer getEncodingWriter(OutputStream out) throws IOException {
    if (encoding == null) {
      return new OutputStreamWriter(out);
    }

    return new OutputStreamWriter(out, encoding);
  }

@@ -234,23 +246,8 @@ public static Encoding defaultEncoding() {
    return DEFAULT_ENCODING;
  }

  /**
   * Test if an encoding is available in the JVM.
   *
   * @param encodingName the JVM encoding name to test
   * @return true iff the encoding is supported
   */
  private static boolean isAvailable(String encodingName) {
    try {
      "DUMMY".getBytes(encodingName); //NOSONAR
      return true;
    } catch (java.io.UnsupportedEncodingException e) {
      return false;
    }
  }

  public String toString() {
    return (encoding == null ? "<default JVM encoding>" : encoding);
    return encoding;
  }

  /**