Java tutorial
/******************************************************************************* * Copyright (c) 2010-2014 SAP AG and others. * All rights reserved. This program and the accompanying materials * are made available under the terms of the Eclipse Public License v1.0 * which accompanies this distribution, and is available at * http://www.eclipse.org/legal/epl-v10.html * * Contributors: * SAP AG - initial API and implementation *******************************************************************************/ package org.eclipse.skalli.core.rest; import java.io.IOException; import java.io.Writer; import java.util.UUID; import org.apache.commons.lang.StringUtils; import org.apache.commons.lang.time.DateFormatUtils; import org.apache.commons.lang.time.DurationFormatUtils; import org.eclipse.skalli.commons.CharacterStack; import org.eclipse.skalli.commons.FormatUtils; import org.eclipse.skalli.services.rest.RestWriter; import org.eclipse.skalli.services.rest.RestWriterBase; import org.restlet.data.MediaType; public class JSONRestWriter extends RestWriterBase implements RestWriter { /** Option to enable @-prefixed attributes. */ public static final int PREFIXED_ATTRIBUTES = 0x10000; /** Option to enable the rendering of namespace atributes. */ public static final int NAMESPACE_ATTRIBUTES = 0x20000; /** Option to allow a key for the root object/array. */ public static final int NAMED_ROOT = 0x40000; private static final MediaType MEDIA_TYPE = MediaType.APPLICATION_JSON; private static final char STATE_INITIAL = '\u03B1'; private static final char STATE_FINAL = '\u03C9'; private static final char STATE_ARRAY = 'A'; private static final char STATE_OBJECT = 'O'; private static final char STATE_ITEM = 'I'; private static final char EXPECT_SEQUENCE = '\u03B1'; private static final char IN_SEQUENCE = ','; private static final char EXPECT_END_SEQUENCE = '\u03C9'; private static final String VALUE_KEY = "value"; //$NON-NLS-1$ private static final String VALUES_KEY = "values"; //$NON-NLS-1$ private static final String MILLIS_KEY = "millis"; //$NON-NLS-1$ private static final String LINKS_KEY = "links"; //$NON-NLS-1$ private static final String LINK_KEY = "link"; //$NON-NLS-1$ private static final String HREF_KEY = "href"; //$NON-NLS-1$ private static final String REL_KEY = "rel"; //$NON-NLS-1$ private static final String XMLNS_PREFIX = "xmlns:"; //$NON-NLS-1$ // stack for state machine private CharacterStack states; // the current state private char state; // state that record whether we are in a sequence of elements, // or expect the begin/end of a sequence; // a sequence is a comma-separated list of elements private char sequenceState; // true, if the next element is the first in a sequence, i.e. // we must not render a comma before the element private boolean firstInSequence; // the key to assign to the next element private String nextKey; public JSONRestWriter(Writer writer, String webLocator) { this(writer, webLocator, 0); } /** * * @param writer * @param options */ public JSONRestWriter(Writer writer, String webLocator, int options) { super(writer, webLocator, options); this.options = options; states = new CharacterStack(); states.push(state = STATE_INITIAL); sequenceState = EXPECT_SEQUENCE; firstInSequence = true; } @Override public MediaType getMediaType() { return MEDIA_TYPE; } @Override public void flush() throws IOException { if (state != STATE_FINAL) { throw new IllegalStateException("Final state not yet reached"); } writer.flush(); } @Override public RestWriter key(String key) { nextKey = StringUtils.isNotBlank(key) ? key : null; return this; } @Override public RestWriter array() throws IOException { if (state == STATE_FINAL) { throw new IllegalStateException("Unexpeced array: Final state already reached"); } if (sequenceState == EXPECT_END_SEQUENCE) { throw new IllegalStateException("Unexpected array after value"); } appendComma(); if (nextKey != null && (state == STATE_OBJECT || (state == STATE_INITIAL && isSet(NAMED_ROOT)))) { appendKey(nextKey); writer.append(':'); } writer.append('['); states.push(state = STATE_ARRAY); sequenceState = IN_SEQUENCE; firstInSequence = true; nextKey = null; return this; } @Override public RestWriter array(String itemKey) throws IOException { return array(); } @Override public RestWriter array(String key, String itemKey) throws IOException { return key(key).array(); } @Override public RestWriter item() throws IOException { if (sequenceState == EXPECT_END_SEQUENCE) { throw new IllegalStateException("Unexpected item after value"); } appendComma(); if (state != STATE_ITEM) { while (state != STATE_ARRAY) { end(); } if (state == STATE_ARRAY) { states.push(state = STATE_ITEM); } } firstInSequence = true; return this; } @Override public RestWriter item(String itemKey) throws IOException { return item(); } @Override public RestWriter object() throws IOException { if (state == STATE_FINAL) { throw new IllegalStateException("Unexpected object: Final state already reached"); } if (sequenceState == EXPECT_END_SEQUENCE) { throw new IllegalStateException("Unexpected object after value"); } appendComma(); if (nextKey != null && (state == STATE_OBJECT || (state == STATE_INITIAL && isSet(NAMED_ROOT)))) { appendKey(nextKey); writer.append(':'); } writer.append('{'); states.push(state = STATE_OBJECT); sequenceState = IN_SEQUENCE; nextKey = null; firstInSequence = true; return this; } @Override public RestWriter object(String key) throws IOException { return key(key).object(); } @Override public RestWriter end() throws IOException { if (state == STATE_FINAL) { throw new IllegalStateException("Final state already reached"); } if (state == STATE_INITIAL) { throw new IllegalStateException("Still in initial state"); } state = states.pop(); if (state == STATE_ARRAY) { writer.append(']'); } else if (state == STATE_OBJECT) { writer.append('}'); } else if (state == STATE_INITIAL) { throw new IllegalStateException("Still in initial state"); } state = states.peek(); if (state == STATE_INITIAL) { state = STATE_FINAL; } sequenceState = IN_SEQUENCE; firstInSequence = false; return this; } @Override public RestWriter links() throws IOException { return links(LINKS_KEY); } @Override public RestWriter links(String key) throws IOException { return key(key).array(); } @Override public RestWriter link(String rel, String href) throws IOException { return object(LINK_KEY).attribute(REL_KEY, rel).attribute(HREF_KEY, href).end(); } @Override public RestWriter value(String s) throws IOException { return value(s, true); } @Override public RestWriter value(long l) throws IOException { return value(l, false); } @Override public RestWriter value(double d) throws IOException { return value(d, false); } @Override public RestWriter value(Number n) throws IOException { return value(n, false); } @Override public RestWriter value(boolean b) throws IOException { return value(b, false); } @Override public RestWriter value(UUID uuid) throws IOException { return value(uuid, true); } @Override public RestWriter href(Object... pathSegments) throws IOException { return value(hrefOf(pathSegments)); } @Override public RestWriter date(long millis) throws IOException { return value(DateFormatUtils.formatUTC(millis, "yyyy-MM-dd")); //$NON-NLS-1$ } @Override public RestWriter datetime(long millis) throws IOException { return value(FormatUtils.formatUTC(millis)); } @Override public RestWriter duration(long millis) throws IOException { return value(DurationFormatUtils.formatDurationISO(millis)); } @Override public RestWriter pair(String key, String s) throws IOException { return value(key, s, true); } @Override public RestWriter pair(String key, long l) throws IOException { return value(key, l, false); } @Override public RestWriter pair(String key, double d) throws IOException { return value(key, d, false); } @Override public RestWriter pair(String key, Number n) throws IOException { return value(key, n, false); } @Override public RestWriter pair(String key, boolean b) throws IOException { return value(key, b, false); } @Override public RestWriter pair(String key, UUID uuid) throws IOException { return value(key, uuid, true); } @Override public RestWriter date(String key, long millis) throws IOException { return object(key).pair(MILLIS_KEY, millis).value(DateFormatUtils.formatUTC(millis, "yyyy-MM-dd")); //$NON-NLS-1$ } @Override public RestWriter datetime(String key, long millis) throws IOException { return object(key).pair(MILLIS_KEY, millis).value(FormatUtils.formatUTC(millis)); } @Override public RestWriter duration(String key, long millis) throws IOException { return object(key).pair(MILLIS_KEY, millis).value(DurationFormatUtils.formatDurationISO(millis)); } @Override public RestWriter href(String key, Object... pathSegments) throws IOException { return pair(key, hrefOf(pathSegments)); } @Override public RestWriter attribute(String name, String value) throws IOException { return attribute(name, value, true); } @Override public RestWriter attribute(String name, long l) throws IOException { return attribute(name, l, false); } @Override public RestWriter attribute(String name, double d) throws IOException { return attribute(name, d, false); } @Override public RestWriter attribute(String name, Number n) throws IOException { return attribute(name, n, false); } @Override public RestWriter attribute(String name, boolean b) throws IOException { return attribute(name, b, false); } @Override public RestWriter attribute(String name, UUID uuid) throws IOException { return attribute(name, uuid, true); } @Override public RestWriter namespace(String name, String value) throws IOException { if (isSet(NAMESPACE_ATTRIBUTES)) { attribute(StringUtils.isBlank(name) ? XMLNS_PREFIX : name, value); } return this; } private void append(String s, boolean quoted) throws IOException { if (quoted) { writer.append('"'); escaped(s); writer.append('"'); } else { escaped(s); } } private void appendComma() throws IOException { if (!firstInSequence) { writer.append(','); } } private void appendKey(String key) throws IOException { append(StringUtils.isBlank(key) ? VALUE_KEY : key, true); } private RestWriter value(Object value, boolean quoted) throws IOException { if (state == STATE_FINAL) { throw new IllegalStateException("Unexpeced value: Final state already reached"); } appendComma(); if (state == STATE_ARRAY || state == STATE_ITEM) { append(value.toString(), quoted); } else if (state == STATE_OBJECT && sequenceState == IN_SEQUENCE) { append(VALUE_KEY, true); writer.append(':'); append(value.toString(), quoted); sequenceState = EXPECT_END_SEQUENCE; } else { throw new IllegalStateException("Unexpected value"); } nextKey = null; firstInSequence = false; return this; } private RestWriter value(String key, Object value, boolean quoted) throws IOException { if (state == STATE_FINAL) { throw new IllegalStateException("Unexpeced named attribute: Final state already reached"); } if (StringUtils.isBlank(key)) { throw new IllegalStateException("Missing key"); } if (state == STATE_OBJECT) { String str = value != null ? value.toString() : null; if (StringUtils.isNotBlank(str) || isSet(ALL_MEMBERS)) { appendComma(); appendKey(key); writer.append(':'); if (str == null) { append("null", false); //$NON-NLS-1$ } else { append(str, quoted); } firstInSequence = false; } } else { throw new IllegalStateException("Unexpected named attribute"); } nextKey = null; return this; } private RestWriter attribute(String name, Object value, boolean quoted) throws IOException { if (state == STATE_FINAL) { throw new IllegalStateException("Unexpeced attribute: Final state already reached"); } String key = isSet(PREFIXED_ATTRIBUTES) ? "@" + name : name; //$NON-NLS-1$ if (sequenceState == IN_SEQUENCE) { if (state == STATE_ARRAY || state == STATE_ITEM) { object(); value(key, value, quoted); end(); } else { value(key, value, quoted); } } else { throw new IllegalStateException("Unexpected attribute"); } nextKey = null; return this; } @SuppressWarnings("nls") private RestWriter escaped(String s) throws IOException { int len = s.length(); for (int i = 0; i < len; ++i) { char c = s.charAt(i); switch (c) { case '"': writer.append("\\\""); break; case '\\': writer.append("\\\\"); break; case '<': writer.append('\u0047'); break; case '\n': writer.append("\\n"); break; case '\r': writer.append("\\r"); break; case '\t': writer.append("\\t"); break; case '\b': writer.append("\\b"); break; case '\f': writer.append("\\f"); break; default: if (c < 0x20 || c >= 0x80 && c <= 0xa0 || c >= '\u2000' && c < '\u2100') { writer.append("\\u"); writer.append(StringUtils.leftPad(Integer.toHexString(c), 4, '0')); } else { writer.append(c); } } } return this; } }