HADOOP-19231. Add JacksonUtil to manage Jackson classes (#6953)

New class org.apache.hadoop.util.JacksonUtil centralizes construction of
Jackson ObjectMappers and JsonFactories.

Contributed by PJ Fanning

Author: pjfanning

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/conf/Configuration.java

@@ -22,7 +22,6 @@
 import com.ctc.wstx.io.StreamBootstrapper;
 import com.ctc.wstx.io.SystemId;
 import com.ctc.wstx.stax.WstxInputFactory;
-import com.fasterxml.jackson.core.JsonFactory;
 import com.fasterxml.jackson.core.JsonGenerator;
 
 import java.io.BufferedInputStream;
@@ -101,6 +100,7 @@
 import org.apache.hadoop.security.alias.CredentialProviderFactory;
 import org.apache.hadoop.thirdparty.com.google.common.base.Strings;
 import org.apache.hadoop.util.ConfigurationHelper;
+import org.apache.hadoop.util.JacksonUtil;
 import org.apache.hadoop.util.Preconditions;
 import org.apache.hadoop.util.ReflectionUtils;
 import org.apache.hadoop.util.StringInterner;
@@ -3792,8 +3792,7 @@ public static void dumpConfiguration(Configuration config,
       throw new IllegalArgumentException("Property " +
           propertyName + " not found");
     } else {
-      JsonFactory dumpFactory = new JsonFactory();
-      JsonGenerator dumpGenerator = dumpFactory.createGenerator(out);
+      JsonGenerator dumpGenerator = JacksonUtil.getSharedWriter().createGenerator(out);
       dumpGenerator.writeStartObject();
       dumpGenerator.writeFieldName("property");
       appendJSONProperty(dumpGenerator, config, propertyName,
@@ -3831,8 +3830,7 @@ public static void dumpConfiguration(Configuration config,
    */
   public static void dumpConfiguration(Configuration config,
       Writer out) throws IOException {
-    JsonFactory dumpFactory = new JsonFactory();
-    JsonGenerator dumpGenerator = dumpFactory.createGenerator(out);
+    JsonGenerator dumpGenerator = JacksonUtil.getSharedWriter().createGenerator(out);
     dumpGenerator.writeStartObject();
     dumpGenerator.writeFieldName("properties");
     dumpGenerator.writeStartArray();

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/crypto/key/kms/KMSClientProvider.java

@@ -41,6 +41,7 @@
 import org.apache.hadoop.security.token.delegation.AbstractDelegationTokenSelector;
 import org.apache.hadoop.security.token.delegation.web.DelegationTokenAuthenticatedURL;
 import org.apache.hadoop.util.HttpExceptionUtils;
+import org.apache.hadoop.util.JacksonUtil;
 import org.apache.hadoop.util.JsonSerialization;
 import org.apache.hadoop.util.KMSUtil;
 import org.apache.http.client.utils.URIBuilder;
@@ -78,7 +79,6 @@
 import org.apache.hadoop.crypto.key.KeyProviderCryptoExtension;
 import org.apache.hadoop.crypto.key.KeyProviderCryptoExtension.CryptoExtension;
 
-import com.fasterxml.jackson.databind.ObjectMapper;
 import org.apache.hadoop.classification.VisibleForTesting;
 import org.apache.hadoop.util.Preconditions;
 import org.apache.hadoop.thirdparty.com.google.common.base.Strings;
@@ -592,11 +592,10 @@ private <T> T call(HttpURLConnection conn, Object jsonOutput,
         && conn.getContentType().trim().toLowerCase()
             .startsWith(APPLICATION_JSON_MIME)
         && klass != null) {
-      ObjectMapper mapper = new ObjectMapper();
       InputStream is = null;
       try {
         is = conn.getInputStream();
-        ret = mapper.readValue(is, klass);
+        ret = JacksonUtil.getSharedReader().readValue(is, klass);
       } finally {
         IOUtils.closeStream(is);
       }

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/DecayRpcScheduler.java

@@ -38,10 +38,10 @@
 
 import javax.management.ObjectName;
 
-import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.databind.ObjectWriter;
 
 import org.apache.hadoop.security.UserGroupInformation;
+import org.apache.hadoop.util.JacksonUtil;
 import org.apache.hadoop.util.Preconditions;
 import org.apache.hadoop.thirdparty.com.google.common.util.concurrent.AtomicDoubleArray;
 import org.apache.commons.lang3.exception.ExceptionUtils;
@@ -146,7 +146,7 @@ public class DecayRpcScheduler implements RpcScheduler,
   public static final Logger LOG =
       LoggerFactory.getLogger(DecayRpcScheduler.class);
 
-  private static final ObjectWriter WRITER = new ObjectMapper().writer();
+  private static final ObjectWriter WRITER = JacksonUtil.getSharedWriter();
 
   // Track the decayed and raw (no decay) number of calls for each schedulable
   // identity from all previous decay windows: idx 0 for decayed call cost and

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/Server.java

@@ -121,6 +121,7 @@
 import org.apache.hadoop.security.token.SecretManager.InvalidToken;
 import org.apache.hadoop.security.token.TokenIdentifier;
 import org.apache.hadoop.util.ExitUtil;
+import org.apache.hadoop.util.JacksonUtil;
 import org.apache.hadoop.util.ProtoUtil;
 import org.apache.hadoop.util.StringUtils;
 import org.apache.hadoop.util.Time;
@@ -130,7 +131,6 @@
 import org.apache.hadoop.tracing.TraceScope;
 import org.apache.hadoop.tracing.Tracer;
 import org.apache.hadoop.tracing.TraceUtils;
-import com.fasterxml.jackson.databind.ObjectMapper;
 import org.apache.hadoop.classification.VisibleForTesting;
 
 import org.apache.hadoop.thirdparty.com.google.common.util.concurrent.ThreadFactoryBuilder;
@@ -3843,9 +3843,8 @@ public int getNumOpenConnections() {
    * @return Get the NumOpenConnections/User.
    */
   public String getNumOpenConnectionsPerUser() {
-    ObjectMapper mapper = new ObjectMapper();
     try {
-      return mapper
+      return JacksonUtil.getSharedWriter()
           .writeValueAsString(connectionManager.getUserToConnectionsMap());
     } catch (IOException ignored) {
     }

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/jmx/JMXJsonServlet.java

@@ -43,13 +43,13 @@
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 
-import com.fasterxml.jackson.core.JsonFactory;
 import com.fasterxml.jackson.core.JsonGenerator;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import org.apache.commons.lang3.NotImplementedException;
 import org.apache.hadoop.http.HttpServer2;
+import org.apache.hadoop.util.JacksonUtil;
 
 /*
  * This servlet is based off of the JMXProxyServlet from Tomcat 7.0.14. It has
@@ -134,19 +134,13 @@ public class JMXJsonServlet extends HttpServlet {
    */
   protected transient MBeanServer mBeanServer;
 
-  /**
-   * Json Factory to create Json generators for write objects in json format
-   */
-  protected transient JsonFactory jsonFactory;
-
   /**
    * Initialize this servlet.
    */
   @Override
   public void init() throws ServletException {
     // Retrieve the MBean server
     mBeanServer = ManagementFactory.getPlatformMBeanServer();
-    jsonFactory = new JsonFactory();
   }
 
   protected boolean isInstrumentationAccessAllowed(HttpServletRequest request, 
@@ -187,7 +181,7 @@ public void doGet(HttpServletRequest request, HttpServletResponse response) {
         response.setHeader(ACCESS_CONTROL_ALLOW_METHODS, "GET");
         response.setHeader(ACCESS_CONTROL_ALLOW_ORIGIN, "*");
 
-        jg = jsonFactory.createGenerator(writer);
+        jg = JacksonUtil.getSharedWriter().createGenerator(writer);
         jg.disable(JsonGenerator.Feature.AUTO_CLOSE_TARGET);
         jg.useDefaultPrettyPrinter();
         jg.writeStartObject();

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/metrics2/MetricsJsonBuilder.java

@@ -21,8 +21,8 @@
 import org.apache.commons.lang3.exception.ExceptionUtils;
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.classification.InterfaceStability;
+import org.apache.hadoop.util.JacksonUtil;
 
-import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.databind.ObjectWriter;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -46,8 +46,7 @@ public class MetricsJsonBuilder extends MetricsRecordBuilder {
   private final MetricsCollector parent;
   private Map<String, Object> innerMetrics = new LinkedHashMap<>();
 
-  private static final ObjectWriter WRITER =
-      new ObjectMapper().writer();
+  private static final ObjectWriter WRITER = JacksonUtil.getSharedWriter();
 
   /**
    * Build an instance.

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/security/token/delegation/web/DelegationTokenAuthenticationHandler.java

@@ -46,6 +46,7 @@
 import org.apache.hadoop.security.token.delegation.AbstractDelegationTokenIdentifier;
 import org.apache.hadoop.security.token.delegation.AbstractDelegationTokenSecretManager;
 import org.apache.hadoop.util.HttpExceptionUtils;
+import org.apache.hadoop.util.JacksonUtil;
 import org.apache.hadoop.util.StringUtils;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -165,7 +166,7 @@ public void initTokenManager(Properties config) {
   @VisibleForTesting
   public void initJsonFactory(Properties config) {
     boolean hasFeature = false;
-    JsonFactory tmpJsonFactory = new JsonFactory();
+    JsonFactory tmpJsonFactory = JacksonUtil.createBasicJsonFactory();
 
     for (Map.Entry entry : config.entrySet()) {
       String key = (String)entry.getKey();
@@ -335,7 +336,7 @@ public boolean managementOperation(AuthenticationToken token,
             if (map != null) {
               response.setContentType(MediaType.APPLICATION_JSON);
               Writer writer = response.getWriter();
-              ObjectMapper jsonMapper = new ObjectMapper(jsonFactory);
+              ObjectMapper jsonMapper = JacksonUtil.createObjectMapper(jsonFactory);
               jsonMapper.writeValue(writer, map);
               writer.write(ENTER);
               writer.flush();

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/JacksonUtil.java

@@ -0,0 +1,123 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF 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.apache.hadoop.util;
+
+import com.fasterxml.jackson.core.JsonFactory;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.ObjectReader;
+import com.fasterxml.jackson.databind.ObjectWriter;
+import com.fasterxml.jackson.databind.json.JsonMapper;
+
+import org.apache.hadoop.classification.InterfaceAudience.Private;
+
+/**
+ * Utility for sharing code related to Jackson usage in Hadoop.
+ */
+@Private
+public final class JacksonUtil {
+
+  private static final ObjectMapper SHARED_BASIC_OBJECT_MAPPER = createBasicObjectMapper();
+  private static final ObjectReader SHARED_BASIC_OBJECT_READER =
+      SHARED_BASIC_OBJECT_MAPPER.reader();
+  private static final ObjectWriter SHARED_BASIC_OBJECT_WRITER =
+      SHARED_BASIC_OBJECT_MAPPER.writer();
+  private static final ObjectWriter SHARED_BASIC_OBJECT_WRITER_PRETTY =
+      SHARED_BASIC_OBJECT_MAPPER.writerWithDefaultPrettyPrinter();
+
+  /**
+   * Creates a new {@link JsonFactory} instance with basic configuration.
+   *
+   * @return an {@link JsonFactory} with basic configuration
+   */
+  public static JsonFactory createBasicJsonFactory() {
+    // deliberately return a new instance instead of sharing one because we can't trust
+    // that users won't modify this instance
+    return new JsonFactory();
+  }
+
+  /**
+   * Creates a new {@link ObjectMapper} instance with basic configuration.
+   *
+   * @return an {@link ObjectMapper} with basic configuration
+   */
+  public static ObjectMapper createBasicObjectMapper() {
+    // deliberately return a new instance instead of sharing one because we can't trust
+    // that users won't modify this instance
+    return JsonMapper.builder(createBasicJsonFactory()).build();
+  }
+
+  /**
+   * Creates a new {@link ObjectMapper} instance based on the configuration
+   * in the input {@link JsonFactory}.
+   *
+   * @param jsonFactory a pre-configured {@link JsonFactory}
+   * @return an {@link ObjectMapper} with configuration set by the input {@link JsonFactory}.
+   */
+  public static ObjectMapper createObjectMapper(final JsonFactory jsonFactory) {
+    return JsonMapper.builder(jsonFactory).build();
+  }
+
+  /**
+   * Returns a shared {@link ObjectReader} instance with basic configuration.
+   *
+   * @return a shared {@link ObjectReader} instance with basic configuration
+   */
+  public static ObjectReader getSharedReader() {
+    return SHARED_BASIC_OBJECT_READER;
+  }
+
+  /**
+   * Returns an {@link ObjectReader} for the given type instance with basic configuration.
+   *
+   * @param type the class that the reader has to support
+   * @return an {@link ObjectReader} instance with basic configuration
+   */
+  public static ObjectReader createBasicReaderFor(Class<?> type) {
+    return SHARED_BASIC_OBJECT_MAPPER.readerFor(type);
+  }
+
+  /**
+   * Returns a shared {@link ObjectWriter} instance with basic configuration.
+   *
+   * @return a shared {@link ObjectWriter} instance with basic configuration
+   */
+  public static ObjectWriter getSharedWriter() {
+    return SHARED_BASIC_OBJECT_WRITER;
+  }
+
+  /**
+   * Returns a shared {@link ObjectWriter} instance with pretty print and basic configuration.
+   *
+   * @return a shared {@link ObjectWriter} instance with pretty print and basic configuration
+   */
+  public static ObjectWriter getSharedWriterWithPrettyPrint() {
+    return SHARED_BASIC_OBJECT_WRITER_PRETTY;
+  }
+
+  /**
+   * Returns an {@link ObjectWriter} for the given type instance with basic configuration.
+   *
+   * @param type the class that the writer has to support
+   * @return an {@link ObjectWriter} instance with basic configuration
+   */
+  public static ObjectWriter createBasicWriterFor(Class<?> type) {
+    return SHARED_BASIC_OBJECT_MAPPER.writerFor(type);
+  }
+
+  private JacksonUtil() {}
+}

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/JsonSerialization.java

@@ -76,11 +76,8 @@ public class JsonSerialization<T> {
   private final Class<T> classType;
   private final ObjectMapper mapper;
 
-  private static final ObjectWriter WRITER =
-      new ObjectMapper().writerWithDefaultPrettyPrinter();
-
-  private static final ObjectReader MAP_READER =
-      new ObjectMapper().readerFor(Map.class);
+  private static final ObjectWriter WRITER = JacksonUtil.getSharedWriterWithPrettyPrint();
+  private static final ObjectReader MAP_READER = JacksonUtil.createBasicReaderFor(Map.class);
 
   /**
    * @return an ObjectWriter which pretty-prints its output
@@ -106,7 +103,7 @@ public JsonSerialization(Class<T> classType,
       boolean failOnUnknownProperties, boolean pretty) {
     Preconditions.checkArgument(classType != null, "null classType");
     this.classType = classType;
-    this.mapper = new ObjectMapper();
+    this.mapper = JacksonUtil.createBasicObjectMapper();
     mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES,
         failOnUnknownProperties);
     mapper.configure(SerializationFeature.INDENT_OUTPUT, pretty);

hadoop-common-project/hadoop-kms/src/main/java/org/apache/hadoop/crypto/key/kms/server/KMSJSONReader.java

@@ -17,9 +17,8 @@
  */
 package org.apache.hadoop.crypto.key.kms.server;
 
-import com.fasterxml.jackson.databind.ObjectMapper;
-
 import org.apache.hadoop.classification.InterfaceAudience;
+import org.apache.hadoop.util.JacksonUtil;
 
 import javax.ws.rs.Consumes;
 import javax.ws.rs.WebApplicationException;
@@ -38,7 +37,6 @@
 @Consumes(MediaType.APPLICATION_JSON)
 @InterfaceAudience.Private
 public class KMSJSONReader implements MessageBodyReader<Object> {
-  private static final ObjectMapper MAPPER = new ObjectMapper();
 
   @Override
   public boolean isReadable(Class<?> type, Type genericType,
@@ -52,6 +50,6 @@ public Object readFrom(Class<Object> type, Type genericType,
       Annotation[] annotations, MediaType mediaType,
       MultivaluedMap<String, String> httpHeaders, InputStream entityStream)
       throws IOException, WebApplicationException {
-    return MAPPER.readValue(entityStream, type);
+    return JacksonUtil.getSharedReader().readValue(entityStream, type);
   }
 }