Add JSON component

components/json/build.gradle.kts

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+plugins {
+  id("me.champeau.jmh")
+}
+
+apply(from = "$rootDir/gradle/java.gradle")
+
+jmh {
+  version = "1.28"
+}

components/json/src/jmh/java/datadog/json/JsonWriterBenchmark.java

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+package datadog.json;
+
+import static java.util.concurrent.TimeUnit.MICROSECONDS;
+import static org.openjdk.jmh.annotations.Mode.AverageTime;
+
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.Fork;
+import org.openjdk.jmh.annotations.OutputTimeUnit;
+import org.openjdk.jmh.infra.Blackhole;
+
+@BenchmarkMode(AverageTime)
+@OutputTimeUnit(MICROSECONDS)
+@Fork(value = 1)
+@SuppressWarnings("unused")
+public class JsonWriterBenchmark {
+  @Benchmark
+  public void writeSimpleArray(Blackhole blackhole) {
+    try (JsonWriter writer = new JsonWriter()) {
+      writer
+          .beginArray()
+          .beginObject()
+          .name("true")
+          .value(true)
+          .endObject()
+          .beginObject()
+          .name("false")
+          .value(false)
+          .endObject()
+          .endArray();
+      blackhole.consume(writer.toString());
+    }
+  }
+
+  @Benchmark
+  public void writeComplexArray(Blackhole blackhole) {
+    try (JsonWriter writer = new JsonWriter()) {
+      writer
+          .beginArray()
+          .value("first level")
+          .beginArray()
+          .value("second level")
+          .beginArray()
+          .value("third level")
+          .beginObject()
+          .name("key")
+          .value("value")
+          .endObject()
+          .beginObject()
+          .name("key")
+          .value("value")
+          .endObject()
+          .endArray() // second level
+          .beginObject()
+          .name("key")
+          .value("value")
+          .endObject()
+          .endArray() // first level
+          .beginObject()
+          .name("key")
+          .value("value")
+          .endObject()
+          .value("last value")
+          .endArray();
+      blackhole.consume(writer.toString());
+    }
+  }
+
+  @Benchmark
+  public void writeComplexObject(Blackhole blackhole) {
+    try (JsonWriter writer = new JsonWriter()) {
+      writer
+          .beginObject()
+          .name("attrs")
+          .beginObject()
+          .name("attr1")
+          .value("value1")
+          .name("attr2")
+          .value("value2")
+          .endObject()
+          .name("data")
+          .beginArray()
+          .beginObject()
+          .name("x")
+          .value(1)
+          .name("y")
+          .value(12.3)
+          .endObject()
+          .beginObject()
+          .name("x")
+          .value(2)
+          .name("y")
+          .value(4.56)
+          .endObject()
+          .beginObject()
+          .name("x")
+          .value(3)
+          .name("y")
+          .value(789)
+          .endObject()
+          .endArray()
+          .endObject();
+      blackhole.consume(writer.toString());
+    }
+  }
+}

components/json/src/main/java/datadog/json/JsonMapper.java

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+package datadog.json;
+
+import java.util.Collection;
+import java.util.Map;
+
+/** Utility class for simple Java structure mapping into JSON strings. */
+public final class JsonMapper {
+
+  private JsonMapper() {}
+
+  /**
+   * Converts a {@link String} to a JSON string.
+   *
+   * @param string The string to convert.
+   * @return The converted JSON string.
+   */
+  public static String toJson(String string) {
+    if (string == null || string.isEmpty()) {
+      return "";
+    }
+    try (JsonWriter writer = new JsonWriter()) {
+      writer.value(string);
+      return writer.toString();
+    }
+  }
+
+  /**
+   * Converts a {@link Map} to a JSON object.
+   *
+   * @param map The map to convert.
+   * @return The converted JSON object as Java string.
+   */
+  public static String toJson(Map<String, ?> map) {
+    if (map == null || map.isEmpty()) {
+      return "{}";
+    }
+    try (JsonWriter writer = new JsonWriter()) {
+      writer.beginObject();
+      for (Map.Entry<String, ?> entry : map.entrySet()) {
+        writer.name(entry.getKey());
+        Object value = entry.getValue();
+        if (value == null) {
+          writer.nullValue();
+        } else if (value instanceof String) {
+          writer.value((String) value);
+        } else if (value instanceof Double) {
+          writer.value((Double) value);
+        } else if (value instanceof Float) {
+          writer.value((Float) value);
+        } else if (value instanceof Long) {
+          writer.value((Long) value);
+        } else if (value instanceof Integer) {
+          writer.value((Integer) value);
+        } else if (value instanceof Boolean) {
+          writer.value((Boolean) value);
+        } else {
+          writer.value(value.toString());
+        }
+      }
+      writer.endObject();
+      return writer.toString();
+    }
+  }
+
+  /**
+   * Converts a {@link Iterable<String>} to a JSON array.
+   *
+   * @param items The iterable to convert.
+   * @return The converted JSON array as Java string.
+   */
+  @SuppressWarnings("DuplicatedCode")
+  public static String toJson(Collection<String> items) {
+    if (items == null || items.isEmpty()) {
+      return "[]";
+    }
+    try (JsonWriter writer = new JsonWriter()) {
+      writer.beginArray();
+      for (String item : items) {
+        writer.value(item);
+      }
+      writer.endArray();
+      return writer.toString();
+    }
+  }
+
+  /**
+   * Converts a String array to a JSON array.
+   *
+   * @param items The array to convert.
+   * @return The converted JSON array as Java string.
+   */
+  @SuppressWarnings("DuplicatedCode")
+  public static String toJson(String[] items) {
+    if (items == null) {
+      return "[]";
+    }
+    try (JsonWriter writer = new JsonWriter()) {
+      writer.beginArray();
+      for (String item : items) {
+        writer.value(item);
+      }
+      writer.endArray();
+      return writer.toString();
+    }
+  }
+}

components/json/src/main/java/datadog/json/JsonStructure.java

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+package datadog.json;
+
+/** The {@link JsonStructure} keeps track of JSON value being built. */
+interface JsonStructure {
+  /**
+   * Begins an object.
+   *
+   * @throws IllegalStateException if the object can not be started at this position.
+   */
+  void beginObject();
+
+  /**
+   * Checks whether the current position is within an object.
+   *
+   * @return {@code true} if the current position is within an object, {@code false} otherwise.
+   */
+  boolean objectStarted();
+
+  /**
+   * Ends the current object.
+   *
+   * @throws IllegalStateException if the current position is not within an object.
+   */
+  void endObject();
+
+  /** Begins an array. */
+  void beginArray();
+
+  /**
+   * Checks whether the current position is within an array.
+   *
+   * @return {@code true} if the current position is within an array, {@code false} otherwise.
+   */
+  boolean arrayStarted();
+
+  /**
+   * Ends the current array.
+   *
+   * @throws IllegalStateException if the current position is not within an array.
+   */
+  void endArray();
+
+  /**
+   * Adds a name to the current object.
+   *
+   * @throws IllegalStateException if the current position is not within an object.
+   */
+  void addName();
+
+  /**
+   * Adds a value.
+   *
+   * @throws IllegalStateException if the current position can not have a value.
+   */
+  void addValue();
+}