[jvm-packages] Expose the global configuration. (dmlc#11238)

Author: trivialfis

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

@@ -0,0 +1,76 @@
+/*
+ Copyright (c) 2025 by Contributors
+
+ Licensed 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 ml.dmlc.xgboost4j.java;
+
+import java.util.HashMap;
+import java.util.Map;
+
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.core.type.TypeReference;
+import com.fasterxml.jackson.databind.ObjectMapper;
+
+/**
+ * Global configuration context for XGBoost.
+ *
+ * @version 3.0.0
+ *
+ * See the parameter document for supported global configuration. The configuration is
+ * restored upon close.
+ */
+public class ConfigContext implements AutoCloseable {
+  String orig;
+
+  ConfigContext() throws XGBoostError {
+    this.orig = getImpl();
+  }
+
+  static String getImpl() throws XGBoostError {
+    String[] config = new String[1];
+    XGBoostJNI.checkCall(XGBoostJNI.XGBGetGlobalConfig(config));
+    return config[0];
+  }
+
+  public static Map<String, Object> get() throws XGBoostError {
+    String jconfig = getImpl();
+    ObjectMapper mapper = new ObjectMapper();
+    try {
+      Map<String, Object> config = mapper.readValue(jconfig,
+          new TypeReference<Map<String, Object>>() {
+          });
+      return config;
+    } catch (JsonProcessingException ex) {
+      throw new XGBoostError("Failed to get the global config due to a decode error.", ex);
+    }
+  }
+
+  public <T> ConfigContext set(String key, T value) throws XGBoostError {
+    HashMap<String, Object> map = new HashMap<String, Object>();
+    map.put(key, value);
+    ObjectMapper mapper = new ObjectMapper();
+    try {
+      String config = mapper.writeValueAsString(map);
+      XGBoostJNI.checkCall(XGBoostJNI.XGBSetGlobalConfig(config));
+    } catch (JsonProcessingException ex) {
+      throw new XGBoostError("Failed to set the global config due to an encode error.", ex);
+    }
+    return this;
+  }
+
+  @Override
+  public void close() throws XGBoostError {
+    XGBoostJNI.checkCall(XGBoostJNI.XGBSetGlobalConfig(this.orig));
+  }
+};

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

@@ -183,4 +183,7 @@ public final static native int XGDMatrixCreateFromArrayInterfaceColumns(
 
   public final static native int XGDMatrixGetQuantileCut(long handle, long[][] outIndptr, float[][] outValues);
 
+  public final static native int XGBSetGlobalConfig(String config);
+
+  public final static native int XGBGetGlobalConfig(String[] out);
 }

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

@@ -1206,10 +1206,6 @@ JNIEXPORT jint JNICALL Java_ml_dmlc_xgboost4j_java_XGBoostJNI_TrackerWaitFor(JNI
 JNIEXPORT jint JNICALL Java_ml_dmlc_xgboost4j_java_XGBoostJNI_TrackerWorkerArgs(
     JNIEnv *jenv, jclass, jlong jhandle, jlong timeout, jobjectArray jout) {
   using namespace xgboost;  // NOLINT
-
-  Json config{Object{}};
-  config["timeout"] = Integer{static_cast<Integer::Int>(timeout)};
-  std::string sconfig = Json::Dump(config);
   auto handle = reinterpret_cast<TrackerHandle>(jhandle);
   char const *args;
   JVM_CHECK_CALL(XGTrackerWorkerArgs(handle, &args));
@@ -1534,3 +1530,37 @@ JNIEXPORT jint JNICALL Java_ml_dmlc_xgboost4j_java_XGBoostJNI_XGDMatrixGetQuanti
 
   return ret;
 }
+
+/*
+ * Class:     ml_dmlc_xgboost4j_java_XGBoostJNI
+ * Method:    XGBSetGlobalConfig
+ * Signature: (Ljava/lang/String;)I
+ */
+JNIEXPORT jint JNICALL Java_ml_dmlc_xgboost4j_java_XGBoostJNI_XGBSetGlobalConfig(JNIEnv *jenv,
+                                                                                 jclass,
+                                                                                 jstring config) {
+  std::unique_ptr<char const, Deleter<char const>> args{
+      jenv->GetStringUTFChars(config, nullptr), [&](char const *ptr) {
+        if (ptr) {
+          jenv->ReleaseStringUTFChars(config, ptr);
+        }
+      }};
+  auto ret = XGBSetGlobalConfig(args.get());
+  JVM_CHECK_CALL(ret);
+  return ret;
+}
+
+/*
+ * Class:     ml_dmlc_xgboost4j_java_XGBoostJNI
+ * Method:    XGBGetGlobalConfig
+ * Signature: ([Ljava/lang/String;)I
+ */
+JNIEXPORT jint JNICALL
+Java_ml_dmlc_xgboost4j_java_XGBoostJNI_XGBGetGlobalConfig(JNIEnv *jenv, jclass, jobjectArray jout) {
+  char const *args;
+  auto ret = XGBGetGlobalConfig(&args);
+  JVM_CHECK_CALL(ret);
+  jstring jret = jenv->NewStringUTF(args);
+  jenv->SetObjectArrayElement(jout, 0, jret);
+  return 0;
+}

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

@@ -0,0 +1,34 @@
+/*
+ Copyright (c) 2025 by Contributors
+
+ Licensed 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 ml.dmlc.xgboost4j.java;
+
+import junit.framework.TestCase;
+import org.junit.Test;
+
+/**
+ * Test cases for the config context.
+ */
+public class ConfigContextTest {
+  @Test
+  public void testBasic() throws XGBoostError {
+    try (ConfigContext ctx = new ConfigContext().set("verbosity", 3)) {
+      int v = (int) ConfigContext.get().get("verbosity");
+      TestCase.assertEquals(3, v);
+    }
+    int v = (int) ConfigContext.get().get("verbosity");
+    TestCase.assertEquals(1, v);
+  }
+}