Java tutorial
/* * Licensed to Elasticsearch under one or more contributor * license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright * ownership. Elasticsearch 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. */ package org.codelibs.elasticsearch.common.xcontent; import org.apache.lucene.util.BytesRef; import org.codelibs.elasticsearch.common.bytes.BytesReference; import org.codelibs.elasticsearch.common.geo.GeoPoint; import org.codelibs.elasticsearch.common.io.BytesStream; import org.codelibs.elasticsearch.common.io.stream.BytesStreamOutput; import org.codelibs.elasticsearch.common.lease.Releasable; import org.codelibs.elasticsearch.common.text.Text; import org.codelibs.elasticsearch.common.unit.ByteSizeValue; import org.codelibs.elasticsearch.common.unit.TimeValue; import org.joda.time.DateTimeZone; import org.joda.time.ReadableInstant; import org.joda.time.format.DateTimeFormatter; import org.joda.time.format.ISODateTimeFormat; import java.io.Flushable; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.nio.file.Path; import java.util.Arrays; import java.util.Calendar; import java.util.Collections; import java.util.Date; import java.util.HashMap; import java.util.IdentityHashMap; import java.util.Locale; import java.util.Map; import java.util.Objects; import java.util.Set; import java.util.concurrent.TimeUnit; /** * A utility to build XContent (ie json). */ public final class XContentBuilder implements BytesStream, Releasable, Flushable { /** * Create a new {XContentBuilder} using the given {XContent} content. * <p> * The builder uses an internal {BytesStreamOutput} output stream to build the content. * </p> * * @param xContent the {XContent} * @return a new {XContentBuilder} * @throws IOException if an {IOException} occurs while building the content */ public static XContentBuilder builder(XContent xContent) throws IOException { return new XContentBuilder(xContent, new BytesStreamOutput()); } /** * Create a new {XContentBuilder} using the given {XContent} content and some inclusive and/or exclusive filters. * <p> * The builder uses an internal {BytesStreamOutput} output stream to build the content. When both exclusive and * inclusive filters are provided, the underlying builder will first use exclusion filters to remove fields and then will check the * remaining fields against the inclusive filters. * <p> * * @param xContent the {XContent} * @param includes the inclusive filters: only fields and objects that match the inclusive filters will be written to the output. * @param excludes the exclusive filters: only fields and objects that don't match the exclusive filters will be written to the output. * @throws IOException if an {IOException} occurs while building the content */ public static XContentBuilder builder(XContent xContent, Set<String> includes, Set<String> excludes) throws IOException { return new XContentBuilder(xContent, new BytesStreamOutput(), includes, excludes); } public static final DateTimeFormatter DEFAULT_DATE_PRINTER = ISODateTimeFormat.dateTime() .withZone(DateTimeZone.UTC); private static final Map<Class<?>, Writer> WRITERS; static { Map<Class<?>, Writer> writers = new HashMap<>(); writers.put(Boolean.class, (b, v) -> b.value((Boolean) v)); writers.put(Byte.class, (b, v) -> b.value((Byte) v)); writers.put(byte[].class, (b, v) -> b.value((byte[]) v)); writers.put(BytesRef.class, (b, v) -> b.binaryValue((BytesRef) v)); writers.put(Date.class, (b, v) -> b.value((Date) v)); writers.put(Double.class, (b, v) -> b.value((Double) v)); writers.put(double[].class, (b, v) -> b.values((double[]) v)); writers.put(Float.class, (b, v) -> b.value((Float) v)); writers.put(float[].class, (b, v) -> b.values((float[]) v)); writers.put(GeoPoint.class, (b, v) -> b.value((GeoPoint) v)); writers.put(Integer.class, (b, v) -> b.value((Integer) v)); writers.put(int[].class, (b, v) -> b.values((int[]) v)); writers.put(Long.class, (b, v) -> b.value((Long) v)); writers.put(long[].class, (b, v) -> b.values((long[]) v)); writers.put(Short.class, (b, v) -> b.value((Short) v)); writers.put(short[].class, (b, v) -> b.values((short[]) v)); writers.put(String.class, (b, v) -> b.value((String) v)); writers.put(String[].class, (b, v) -> b.values((String[]) v)); writers.put(Text.class, (b, v) -> b.value((Text) v)); WRITERS = Collections.unmodifiableMap(writers); } @FunctionalInterface private interface Writer { void write(XContentBuilder builder, Object value) throws IOException; } /** * XContentGenerator used to build the XContent object */ private final XContentGenerator generator; /** * Output stream to which the built object is written */ private final OutputStream bos; /** * When this flag is set to true, some types of values are written in a format easier to read for a human. */ private boolean humanReadable = false; /** * Constructs a new builder using the provided XContent and an OutputStream. Make sure * to call {#close()} when the builder is done with. */ public XContentBuilder(XContent xContent, OutputStream bos) throws IOException { this(xContent, bos, Collections.emptySet(), Collections.emptySet()); } /** * Constructs a new builder using the provided XContent, an OutputStream and * some filters. If filters are specified, only those values matching a * filter will be written to the output stream. Make sure to call * {#close()} when the builder is done with. */ public XContentBuilder(XContent xContent, OutputStream bos, Set<String> includes) throws IOException { this(xContent, bos, includes, Collections.emptySet()); } /** * Creates a new builder using the provided XContent, output stream and some inclusive and/or exclusive filters. When both exclusive and * inclusive filters are provided, the underlying builder will first use exclusion filters to remove fields and then will check the * remaining fields against the inclusive filters. * <p> * Make sure to call {#close()} when the builder is done with. * * @param os the output stream * @param includes the inclusive filters: only fields and objects that match the inclusive filters will be written to the output. * @param excludes the exclusive filters: only fields and objects that don't match the exclusive filters will be written to the output. */ public XContentBuilder(XContent xContent, OutputStream os, Set<String> includes, Set<String> excludes) throws IOException { this.bos = os; this.generator = xContent.createGenerator(bos, includes, excludes); } public XContentType contentType() { return generator.contentType(); } public XContentBuilder prettyPrint() { generator.usePrettyPrint(); return this; } public boolean isPrettyPrint() { return generator.isPrettyPrint(); } /** * Indicate that the current {XContentBuilder} must write a line feed ("\n") * at the end of the built object. * <p> * This only applies for JSON XContent type. It has no effect for other types. */ public XContentBuilder lfAtEnd() { generator.usePrintLineFeedAtEnd(); return this; } /** * Set the "human readable" flag. Once set, some types of values are written in a * format easier to read for a human. */ public XContentBuilder humanReadable(boolean humanReadable) { this.humanReadable = humanReadable; return this; } /** * @return the value of the "human readable" flag. When the value is equal to true, * some types of values are written in a format easier to read for a human. */ public boolean humanReadable() { return this.humanReadable; } //////////////////////////////////////////////////////////////////////////// // Structure (object, array, field, null values...) ////////////////////////////////// public XContentBuilder startObject() throws IOException { generator.writeStartObject(); return this; } public XContentBuilder startObject(String name) throws IOException { return field(name).startObject(); } public XContentBuilder endObject() throws IOException { generator.writeEndObject(); return this; } public XContentBuilder startArray() throws IOException { generator.writeStartArray(); return this; } public XContentBuilder startArray(String name) throws IOException { return field(name).startArray(); } public XContentBuilder endArray() throws IOException { generator.writeEndArray(); return this; } public XContentBuilder field(String name) throws IOException { ensureNameNotNull(name); generator.writeFieldName(name); return this; } public XContentBuilder nullField(String name) throws IOException { ensureNameNotNull(name); generator.writeNullField(name); return this; } public XContentBuilder nullValue() throws IOException { generator.writeNull(); return this; } //////////////////////////////////////////////////////////////////////////// // Boolean ////////////////////////////////// public XContentBuilder field(String name, Boolean value) throws IOException { return (value == null) ? nullField(name) : field(name, value.booleanValue()); } public XContentBuilder field(String name, boolean value) throws IOException { ensureNameNotNull(name); generator.writeBooleanField(name, value); return this; } public XContentBuilder array(String name, boolean[] values) throws IOException { return field(name).values(values); } private XContentBuilder values(boolean[] values) throws IOException { if (values == null) { return nullValue(); } startArray(); for (boolean b : values) { value(b); } endArray(); return this; } public XContentBuilder value(Boolean value) throws IOException { return (value == null) ? nullValue() : value(value.booleanValue()); } public XContentBuilder value(boolean value) throws IOException { generator.writeBoolean(value); return this; } //////////////////////////////////////////////////////////////////////////// // Byte ////////////////////////////////// public XContentBuilder field(String name, Byte value) throws IOException { return (value == null) ? nullField(name) : field(name, value.byteValue()); } public XContentBuilder field(String name, byte value) throws IOException { return field(name).value(value); } public XContentBuilder value(Byte value) throws IOException { return (value == null) ? nullValue() : value(value.byteValue()); } public XContentBuilder value(byte value) throws IOException { generator.writeNumber(value); return this; } //////////////////////////////////////////////////////////////////////////// // Double ////////////////////////////////// public XContentBuilder field(String name, Double value) throws IOException { return (value == null) ? nullField(name) : field(name, value.doubleValue()); } public XContentBuilder field(String name, double value) throws IOException { ensureNameNotNull(name); generator.writeNumberField(name, value); return this; } public XContentBuilder array(String name, double[] values) throws IOException { return field(name).values(values); } private XContentBuilder values(double[] values) throws IOException { if (values == null) { return nullValue(); } startArray(); for (double b : values) { value(b); } endArray(); return this; } public XContentBuilder value(Double value) throws IOException { return (value == null) ? nullValue() : value(value.doubleValue()); } public XContentBuilder value(double value) throws IOException { generator.writeNumber(value); return this; } //////////////////////////////////////////////////////////////////////////// // Float ////////////////////////////////// public XContentBuilder field(String name, Float value) throws IOException { return (value == null) ? nullField(name) : field(name, value.floatValue()); } public XContentBuilder field(String name, float value) throws IOException { ensureNameNotNull(name); generator.writeNumberField(name, value); return this; } public XContentBuilder array(String name, float[] values) throws IOException { return field(name).values(values); } private XContentBuilder values(float[] values) throws IOException { if (values == null) { return nullValue(); } startArray(); for (float f : values) { value(f); } endArray(); return this; } public XContentBuilder value(Float value) throws IOException { return (value == null) ? nullValue() : value(value.floatValue()); } public XContentBuilder value(float value) throws IOException { generator.writeNumber(value); return this; } //////////////////////////////////////////////////////////////////////////// // Integer ////////////////////////////////// public XContentBuilder field(String name, Integer value) throws IOException { return (value == null) ? nullField(name) : field(name, value.intValue()); } public XContentBuilder field(String name, int value) throws IOException { ensureNameNotNull(name); generator.writeNumberField(name, value); return this; } public XContentBuilder array(String name, int[] values) throws IOException { return field(name).values(values); } private XContentBuilder values(int[] values) throws IOException { if (values == null) { return nullValue(); } startArray(); for (int i : values) { value(i); } endArray(); return this; } public XContentBuilder value(Integer value) throws IOException { return (value == null) ? nullValue() : value(value.intValue()); } public XContentBuilder value(int value) throws IOException { generator.writeNumber(value); return this; } //////////////////////////////////////////////////////////////////////////// // Long ////////////////////////////////// public XContentBuilder field(String name, Long value) throws IOException { return (value == null) ? nullField(name) : field(name, value.longValue()); } public XContentBuilder field(String name, long value) throws IOException { ensureNameNotNull(name); generator.writeNumberField(name, value); return this; } public XContentBuilder array(String name, long[] values) throws IOException { return field(name).values(values); } private XContentBuilder values(long[] values) throws IOException { if (values == null) { return nullValue(); } startArray(); for (long l : values) { value(l); } endArray(); return this; } public XContentBuilder value(Long value) throws IOException { return (value == null) ? nullValue() : value(value.longValue()); } public XContentBuilder value(long value) throws IOException { generator.writeNumber(value); return this; } //////////////////////////////////////////////////////////////////////////// // Short ////////////////////////////////// public XContentBuilder field(String name, Short value) throws IOException { return (value == null) ? nullField(name) : field(name, value.shortValue()); } public XContentBuilder field(String name, short value) throws IOException { return field(name).value(value); } public XContentBuilder array(String name, short[] values) throws IOException { return field(name).values(values); } private XContentBuilder values(short[] values) throws IOException { if (values == null) { return nullValue(); } startArray(); for (short s : values) { value(s); } endArray(); return this; } public XContentBuilder value(Short value) throws IOException { return (value == null) ? nullValue() : value(value.shortValue()); } public XContentBuilder value(short value) throws IOException { generator.writeNumber(value); return this; } //////////////////////////////////////////////////////////////////////////// // String ////////////////////////////////// public XContentBuilder field(String name, String value) throws IOException { if (value == null) { return nullField(name); } ensureNameNotNull(name); generator.writeStringField(name, value); return this; } public XContentBuilder array(String name, String... values) throws IOException { return field(name).values(values); } private XContentBuilder values(String[] values) throws IOException { if (values == null) { return nullValue(); } startArray(); for (String s : values) { value(s); } endArray(); return this; } public XContentBuilder value(String value) throws IOException { if (value == null) { return nullValue(); } generator.writeString(value); return this; } //////////////////////////////////////////////////////////////////////////// // Binary ////////////////////////////////// public XContentBuilder field(String name, byte[] value) throws IOException { if (value == null) { return nullField(name); } ensureNameNotNull(name); generator.writeBinaryField(name, value); return this; } public XContentBuilder value(byte[] value) throws IOException { if (value == null) { return nullValue(); } generator.writeBinary(value); return this; } public XContentBuilder field(String name, byte[] value, int offset, int length) throws IOException { return field(name).value(value, offset, length); } public XContentBuilder value(byte[] value, int offset, int length) throws IOException { if (value == null) { return nullValue(); } generator.writeBinary(value, offset, length); return this; } /** * Writes the binary content of the given {BytesRef}. * * Use {org.codelibs.elasticsearch.common.xcontent.XContentParser#binaryValue()} to read the value back */ public XContentBuilder field(String name, BytesRef value) throws IOException { return field(name).binaryValue(value); } /** * Writes the binary content of the given {BytesRef} as UTF-8 bytes. * * Use {XContentParser#utf8Bytes()} to read the value back */ public XContentBuilder utf8Field(String name, BytesRef value) throws IOException { return field(name).utf8Value(value); } /** * Writes the binary content of the given {BytesRef}. * * Use {org.codelibs.elasticsearch.common.xcontent.XContentParser#binaryValue()} to read the value back */ public XContentBuilder binaryValue(BytesRef value) throws IOException { if (value == null) { return nullValue(); } value(value.bytes, value.offset, value.length); return this; } /** * Writes the binary content of the given {BytesRef} as UTF-8 bytes. * * Use {XContentParser#utf8Bytes()} to read the value back */ public XContentBuilder utf8Value(BytesRef value) throws IOException { if (value == null) { return nullValue(); } generator.writeUTF8String(value.bytes, value.offset, value.length); return this; } /** * Writes the binary content of the given {BytesReference}. * * Use {org.codelibs.elasticsearch.common.xcontent.XContentParser#binaryValue()} to read the value back */ public XContentBuilder field(String name, BytesReference value) throws IOException { return field(name).value(value); } /** * Writes the binary content of the given {BytesReference}. * * Use {org.codelibs.elasticsearch.common.xcontent.XContentParser#binaryValue()} to read the value back */ public XContentBuilder value(BytesReference value) throws IOException { return (value == null) ? nullValue() : binaryValue(value.toBytesRef()); } //////////////////////////////////////////////////////////////////////////// // Text ////////////////////////////////// public XContentBuilder field(String name, Text value) throws IOException { return field(name).value(value); } public XContentBuilder value(Text value) throws IOException { if (value == null) { return nullValue(); } else if (value.hasString()) { return value(value.string()); } else { // TODO: TextBytesOptimization we can use a buffer here to convert it? maybe add a // request to jackson to support InputStream as well? return utf8Value(value.bytes().toBytesRef()); } } //////////////////////////////////////////////////////////////////////////// // Date ////////////////////////////////// public XContentBuilder field(String name, ReadableInstant value) throws IOException { return field(name).value(value); } public XContentBuilder field(String name, ReadableInstant value, DateTimeFormatter formatter) throws IOException { return field(name).value(value, formatter); } public XContentBuilder value(ReadableInstant value) throws IOException { return value(value, DEFAULT_DATE_PRINTER); } public XContentBuilder value(ReadableInstant value, DateTimeFormatter formatter) throws IOException { if (value == null) { return nullValue(); } ensureFormatterNotNull(formatter); return value(formatter.print(value)); } public XContentBuilder field(String name, Date value) throws IOException { return field(name).value(value); } public XContentBuilder field(String name, Date value, DateTimeFormatter formatter) throws IOException { return field(name).value(value, formatter); } public XContentBuilder value(Date value) throws IOException { return value(value, DEFAULT_DATE_PRINTER); } public XContentBuilder value(Date value, DateTimeFormatter formatter) throws IOException { if (value == null) { return nullValue(); } return value(formatter, value.getTime()); } public XContentBuilder dateField(String name, String readableName, long value) throws IOException { if (humanReadable) { field(readableName).value(DEFAULT_DATE_PRINTER, value); } field(name, value); return this; } XContentBuilder value(Calendar value) throws IOException { if (value == null) { return nullValue(); } return value(DEFAULT_DATE_PRINTER, value.getTimeInMillis()); } XContentBuilder value(DateTimeFormatter formatter, long value) throws IOException { ensureFormatterNotNull(formatter); return value(formatter.print(value)); } //////////////////////////////////////////////////////////////////////////// // GeoPoint & LatLon ////////////////////////////////// public XContentBuilder field(String name, GeoPoint value) throws IOException { return field(name).value(value); } public XContentBuilder value(GeoPoint value) throws IOException { if (value == null) { return nullValue(); } return latlon(value.getLat(), value.getLon()); } public XContentBuilder latlon(String name, double lat, double lon) throws IOException { return field(name).latlon(lat, lon); } public XContentBuilder latlon(double lat, double lon) throws IOException { return startObject().field("lat", lat).field("lon", lon).endObject(); } //////////////////////////////////////////////////////////////////////////// // Path ////////////////////////////////// public XContentBuilder value(Path value) throws IOException { if (value == null) { return nullValue(); } return value(value.toString()); } //////////////////////////////////////////////////////////////////////////// // Objects // // These methods are used when the type of value is unknown. It tries to fallback // on typed methods and use Object.toString() as a last resort. Always prefer using // typed methods over this. ////////////////////////////////// public XContentBuilder field(String name, Object value) throws IOException { return field(name).value(value); } public XContentBuilder array(String name, Object... values) throws IOException { return field(name).values(values); } XContentBuilder values(Object[] values) throws IOException { if (values == null) { return nullValue(); } // checks that the array of object does not contain references to itself because // iterating over entries will cause a stackoverflow error ensureNoSelfReferences(values); startArray(); for (Object o : values) { value(o); } endArray(); return this; } public XContentBuilder value(Object value) throws IOException { unknownValue(value); return this; } private void unknownValue(Object value) throws IOException { if (value == null) { nullValue(); return; } Writer writer = WRITERS.get(value.getClass()); if (writer != null) { writer.write(this, value); } else if (value instanceof Path) { //Path implements Iterable<Path> and causes endless recursion and a StackOverFlow if treated as an Iterable here value((Path) value); } else if (value instanceof Map) { map((Map) value); } else if (value instanceof Iterable) { value((Iterable<?>) value); } else if (value instanceof Object[]) { values((Object[]) value); } else if (value instanceof Calendar) { value((Calendar) value); } else if (value instanceof ReadableInstant) { value((ReadableInstant) value); } else if (value instanceof BytesReference) { value((BytesReference) value); } else if (value instanceof ToXContent) { value((ToXContent) value); } else { // This is a "value" object (like enum, DistanceUnit, etc) just toString() it // (yes, it can be misleading when toString a Java class, but really, jackson should be used in that case) value(Objects.toString(value)); } } //////////////////////////////////////////////////////////////////////////// // ToXContent ////////////////////////////////// public XContentBuilder field(String name, ToXContent value) throws IOException { return field(name).value(value); } public XContentBuilder field(String name, ToXContent value, ToXContent.Params params) throws IOException { return field(name).value(value, params); } private XContentBuilder value(ToXContent value) throws IOException { return value(value, ToXContent.EMPTY_PARAMS); } private XContentBuilder value(ToXContent value, ToXContent.Params params) throws IOException { if (value == null) { return nullValue(); } value.toXContent(this, params); return this; } //////////////////////////////////////////////////////////////////////////// // Maps & Iterable ////////////////////////////////// public XContentBuilder field(String name, Map<String, Object> values) throws IOException { return field(name).map(values); } public XContentBuilder map(Map<String, ?> values) throws IOException { if (values == null) { return nullValue(); } // checks that the map does not contain references to itself because // iterating over map entries will cause a stackoverflow error ensureNoSelfReferences(values); startObject(); for (Map.Entry<String, ?> value : values.entrySet()) { field(value.getKey()); unknownValue(value.getValue()); } endObject(); return this; } public XContentBuilder field(String name, Iterable<?> values) throws IOException { return field(name).value(values); } private XContentBuilder value(Iterable<?> values) throws IOException { if (values == null) { return nullValue(); } if (values instanceof Path) { //treat as single value value((Path) values); } else { // checks that the iterable does not contain references to itself because // iterating over entries will cause a stackoverflow error ensureNoSelfReferences(values); startArray(); for (Object value : values) { unknownValue(value); } endArray(); } return this; } //////////////////////////////////////////////////////////////////////////// // Misc. ////////////////////////////////// public XContentBuilder timeValueField(String rawFieldName, String readableFieldName, TimeValue timeValue) throws IOException { if (humanReadable) { field(readableFieldName, timeValue.toString()); } field(rawFieldName, timeValue.millis()); return this; } public XContentBuilder timeValueField(String rawFieldName, String readableFieldName, long rawTime) throws IOException { if (humanReadable) { field(readableFieldName, new TimeValue(rawTime).toString()); } field(rawFieldName, rawTime); return this; } public XContentBuilder timeValueField(String rawFieldName, String readableFieldName, long rawTime, TimeUnit timeUnit) throws IOException { if (humanReadable) { field(readableFieldName, new TimeValue(rawTime, timeUnit).toString()); } field(rawFieldName, rawTime); return this; } public XContentBuilder percentageField(String rawFieldName, String readableFieldName, double percentage) throws IOException { if (humanReadable) { field(readableFieldName, String.format(Locale.ROOT, "%1.1f%%", percentage)); } field(rawFieldName, percentage); return this; } public XContentBuilder byteSizeField(String rawFieldName, String readableFieldName, ByteSizeValue byteSizeValue) throws IOException { if (humanReadable) { field(readableFieldName, byteSizeValue.toString()); } field(rawFieldName, byteSizeValue.getBytes()); return this; } public XContentBuilder byteSizeField(String rawFieldName, String readableFieldName, long rawSize) throws IOException { if (humanReadable) { field(readableFieldName, new ByteSizeValue(rawSize).toString()); } field(rawFieldName, rawSize); return this; } //////////////////////////////////////////////////////////////////////////// // Raw fields ////////////////////////////////// public XContentBuilder rawField(String name, InputStream value) throws IOException { generator.writeRawField(name, value); return this; } public XContentBuilder rawField(String name, BytesReference value) throws IOException { generator.writeRawField(name, value); return this; } public XContentBuilder rawValue(BytesReference value) throws IOException { generator.writeRawValue(value); return this; } public XContentBuilder copyCurrentStructure(XContentParser parser) throws IOException { generator.copyCurrentStructure(parser); return this; } @Override public void flush() throws IOException { generator.flush(); } @Override public void close() { try { generator.close(); } catch (IOException e) { throw new IllegalStateException("Failed to close the XContentBuilder", e); } } public XContentGenerator generator() { return this.generator; } @Override public BytesReference bytes() { close(); return ((BytesStream) bos).bytes(); } /** * Returns a string representation of the builder (only applicable for text based xcontent). */ public String string() throws IOException { return bytes().utf8ToString(); } static void ensureNameNotNull(String name) { ensureNotNull(name, "Field name cannot be null"); } static void ensureFormatterNotNull(DateTimeFormatter formatter) { ensureNotNull(formatter, "DateTimeFormatter cannot be null"); } static void ensureNotNull(Object value, String message) { if (value == null) { throw new IllegalArgumentException(message); } } static void ensureNoSelfReferences(Object value) { ensureNoSelfReferences(value, Collections.newSetFromMap(new IdentityHashMap<>())); } private static void ensureNoSelfReferences(final Object value, final Set<Object> ancestors) { if (value != null) { Iterable<?> it; if (value instanceof Map) { it = ((Map) value).values(); } else if ((value instanceof Iterable) && (value instanceof Path == false)) { it = (Iterable) value; } else if (value instanceof Object[]) { it = Arrays.asList((Object[]) value); } else { return; } if (ancestors.add(value) == false) { throw new IllegalArgumentException("Object has already been built and is self-referencing itself"); } for (Object o : it) { ensureNoSelfReferences(o, ancestors); } ancestors.remove(value); } } }