[jvm-packages] Implement new save_raw in jvm-packages. (#7570)

* New `toByteArray` that accepts a parameter for format.

jvm-packages/xgboost4j-spark/src/main/scala/ml/dmlc/xgboost4j/scala/spark/XGBoost.scala

@@ -683,5 +683,3 @@ private object Watches {
     new Watches(Array(trainMatrix, testMatrix), Array("train", "test"), cacheDirName)
   }
 }
-
-

jvm-packages/xgboost4j/src/main/java/ml/dmlc/xgboost4j/java/Booster.java

@@ -1,5 +1,5 @@
 /*
- Copyright (c) 2014,2021 by Contributors
+ Copyright (c) 2014-2022 by Contributors
 
  Licensed under the Apache License, Version 2.0 (the "License");
  you may not use this file except in compliance with the License.
@@ -636,13 +636,27 @@ public class Booster implements Serializable, KryoSerializable {
   }
 
   /**
+   * Save model into raw byte array. Currently it's using the deprecated format as
+   * default, which will be changed into `ubj` in future releases.
    *
-   * @return the saved byte array.
+   * @return the saved byte array
    * @throws XGBoostError native error
    */
   public byte[] toByteArray() throws XGBoostError {
+    return this.toByteArray("deprecated");
+  }
+
+  /**
+   * Save model into raw byte array.
+   *
+   * @param format The output format.  Available options are "json", "ubj" and "deprecated".
+   *
+   * @return the saved byte array
+   * @throws XGBoostError native error
+   */
+  public byte[] toByteArray(String format) throws XGBoostError {
     byte[][] bytes = new byte[1][];
-    XGBoostJNI.checkCall(XGBoostJNI.XGBoosterGetModelRaw(this.handle, bytes));
+    XGBoostJNI.checkCall(XGBoostJNI.XGBoosterSaveModelToBuffer(this.handle, format, bytes));
     return bytes[0];
   }
 

jvm-packages/xgboost4j/src/main/java/ml/dmlc/xgboost4j/java/XGBoostJNI.java

@@ -1,5 +1,5 @@
 /*
- Copyright (c) 2014 by Contributors
+ Copyright (c) 2014-2022 by Contributors
 
  Licensed under the Apache License, Version 2.0 (the "License");
  you may not use this file except in compliance with the License.
@@ -107,7 +107,7 @@ class XGBoostJNI {
 
   public final static native int XGBoosterLoadModelFromBuffer(long handle, byte[] bytes);
 
-  public final static native int XGBoosterGetModelRaw(long handle, byte[][] out_bytes);
+  public final static native int XGBoosterSaveModelToBuffer(long handle, String format, byte[][] out_bytes);
 
   public final static native int XGBoosterDumpModelEx(long handle, String fmap, int with_stats,
                                                       String format, String[][] out_strings);

jvm-packages/xgboost4j/src/main/scala/ml/dmlc/xgboost4j/scala/Booster.scala

@@ -1,5 +1,5 @@
 /*
- Copyright (c) 2014 by Contributors
+ Copyright (c) 2014-2022 by Contributors
 
  Licensed under the Apache License, Version 2.0 (the "License");
  you may not use this file except in compliance with the License.
@@ -301,6 +301,19 @@ class Booster private[xgboost4j](private[xgboost4j] var booster: JBooster)
 
   def getVersion: Int = booster.getVersion
 
+  /**
+    * Save model into a raw byte array.  Available options are "json", "ubj" and "deprecated".
+    */
+  @throws(classOf[XGBoostError])
+  def toByteArray(format: String): Array[Byte] = {
+    booster.toByteArray(format)
+  }
+
+  /**
+    * Save model into a raw byte array. Currently it's using the deprecated format as
+   *  default, which will be changed into `ubj` in future releases.
+    */
+  @throws(classOf[XGBoostError])
   def toByteArray: Array[Byte] = {
     booster.toByteArray
   }

jvm-packages/xgboost4j/src/native/xgboost4j.cpp

@@ -662,17 +662,22 @@ JNIEXPORT jint JNICALL Java_ml_dmlc_xgboost4j_java_XGBoostJNI_XGBoosterLoadModel
 
 /*
  * Class:     ml_dmlc_xgboost4j_java_XGBoostJNI
- * Method:    XGBoosterGetModelRaw
+ * Method:    XGBoosterSaveModelToBuffer
- * Signature: (J[[B)I
+ * Signature: (JLjava/lang/String;[[B)I
  */
-JNIEXPORT jint JNICALL Java_ml_dmlc_xgboost4j_java_XGBoostJNI_XGBoosterGetModelRaw
+JNIEXPORT jint JNICALL Java_ml_dmlc_xgboost4j_java_XGBoostJNI_XGBoosterSaveModelToBuffer
-  (JNIEnv * jenv, jclass jcls, jlong jhandle, jobjectArray jout) {
+  (JNIEnv * jenv, jclass jcls, jlong jhandle, jstring jformat, jobjectArray jout) {
   BoosterHandle handle = (BoosterHandle) jhandle;
+  const char *format = jenv->GetStringUTFChars(jformat, 0);
   bst_ulong len = 0;
-  const char* result;
+  const char *result{nullptr};
-  int ret = XGBoosterGetModelRaw(handle, &len, &result);
+  xgboost::Json config {xgboost::Object{}};
-  JVM_CHECK_CALL(ret);
+  config["format"] = std::string{format};
+  std::string config_str;
+  xgboost::Json::Dump(config, &config_str);
 
+  int ret = XGBoosterSaveModelToBuffer(handle, config_str.c_str(), &len, &result);
+  JVM_CHECK_CALL(ret);
   if (result) {
     jbyteArray jarray = jenv->NewByteArray(len);
     jenv->SetByteArrayRegion(jarray, 0, len, (jbyte *)result);

jvm-packages/xgboost4j/src/native/xgboost4j.h

@@ -209,11 +209,11 @@ JNIEXPORT jint JNICALL Java_ml_dmlc_xgboost4j_java_XGBoostJNI_XGBoosterLoadModel
 
 /*
  * Class:     ml_dmlc_xgboost4j_java_XGBoostJNI
- * Method:    XGBoosterGetModelRaw
+ * Method:    XGBoosterSaveModelToBuffer
- * Signature: (J[[B)I
+ * Signature: (JLjava/lang/String;[[B)I
  */
-JNIEXPORT jint JNICALL Java_ml_dmlc_xgboost4j_java_XGBoostJNI_XGBoosterGetModelRaw
+JNIEXPORT jint JNICALL Java_ml_dmlc_xgboost4j_java_XGBoostJNI_XGBoosterSaveModelToBuffer
-  (JNIEnv *, jclass, jlong, jobjectArray);
+  (JNIEnv *, jclass, jlong, jstring, jobjectArray);
 
 /*
  * Class:     ml_dmlc_xgboost4j_java_XGBoostJNI

jvm-packages/xgboost4j/src/test/java/ml/dmlc/xgboost4j/java/BoosterImplTest.java

@@ -1,5 +1,5 @@
 /*
- Copyright (c) 2014-2021 by Contributors
+ Copyright (c) 2014-2022 by Contributors
 
  Licensed under the Apache License, Version 2.0 (the "License");
  you may not use this file except in compliance with the License.
@@ -115,7 +115,9 @@ public class BoosterImplTest {
     booster.saveModel(temp.getAbsolutePath());
 
     Booster bst2 = XGBoost.loadModel(temp.getAbsolutePath());
-    assert (Arrays.equals(bst2.toByteArray(), booster.toByteArray()));
+    assert (Arrays.equals(bst2.toByteArray("ubj"), booster.toByteArray("ubj")));
+    assert (Arrays.equals(bst2.toByteArray("json"), booster.toByteArray("json")));
+    assert (Arrays.equals(bst2.toByteArray("deprecated"), booster.toByteArray("deprecated")));
     float[][] predicts2 = bst2.predict(testMat, true, 0);
     TestCase.assertTrue(eval.eval(predicts2, testMat) < 0.1f);
   }

jvm-packages/xgboost4j/src/test/scala/ml/dmlc/xgboost4j/scala/ScalaBoosterImplSuite.scala

@@ -1,5 +1,5 @@
 /*
- Copyright (c) 2014 by Contributors
+ Copyright (c) 2014-2022 by Contributors
 
  Licensed under the Apache License, Version 2.0 (the "License");
  you may not use this file except in compliance with the License.
@@ -117,6 +117,7 @@ class ScalaBoosterImplSuite extends FunSuite {
 
     val bst2: Booster = XGBoost.loadModel(temp.getAbsolutePath)
     assert(java.util.Arrays.equals(bst2.toByteArray, booster.toByteArray))
+    assert(java.util.Arrays.equals(bst2.toByteArray("ubj"), booster.toByteArray("ubj")))
     val predicts2: Array[Array[Float]] = bst2.predict(testMat, true, 0)
     TestCase.assertTrue(eval.eval(predicts2, testMat) < 0.1f)
   }