Add AbstractSerializableError and make RemoteException non-final (#1415)

Add `AbstractSerializableError` and make `RemoteException` non-final

Author: mpritham

errors/src/main/java/com/palantir/conjure/java/api/errors/AbstractSerializableError.java

@@ -0,0 +1,69 @@
+/*
+ * (c) Copyright 2025 Palantir Technologies Inc. All rights reserved.
+ *
+ * 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 com.palantir.conjure.java.api.errors;
+
+/**
+ * Base class for serializable Conjure errors with generic parameter type support.
+ * <p>
+ * This abstract class represents serialized Conjure errors. It supports generic parameter types to allow for
+ * deserialization of custom error parameters.
+ * <p>
+ * Usage example where {@code CustomErrorParameters} is a user-defined class representing the error parameters:
+ * <pre>
+ * {@code
+ * class CustomError extends AbstractSerializableError<CustomErrorParameters> {
+ *     @JsonCreator(mode = JsonCreator.Mode.PROPERTIES)
+ *     CustomError(
+ *         @JsonProperty("errorCode") String errorCode,
+ *         @JsonProperty("errorName") String errorName,
+ *         @JsonProperty("errorInstanceId") String errorInstanceId,
+ *         @JsonProperty("parameters") CustomErrorParameters parameters) {
+ *         super(errorCode, errorName, errorInstanceId, parameters);
+ *     }
+ * }
+ * }
+ * </pre>
+ */
+public abstract class AbstractSerializableError<T> {
+    private final String errorCode;
+    private final String errorName;
+    private final String errorInstanceId;
+    private final T parameters;
+
+    public final String errorCode() {
+        return errorCode;
+    }
+
+    public final String errorName() {
+        return errorName;
+    }
+
+    public final String errorInstanceId() {
+        return errorInstanceId;
+    }
+
+    public final T parameters() {
+        return parameters;
+    }
+
+    protected AbstractSerializableError(String errorCode, String errorName, String errorInstanceId, T parameters) {
+        this.errorCode = errorCode;
+        this.errorName = errorName;
+        this.errorInstanceId = errorInstanceId;
+        this.parameters = parameters;
+    }
+}

errors/src/main/java/com/palantir/conjure/java/api/errors/RemoteException.java

@@ -23,8 +23,13 @@
 import java.util.Collections;
 import java.util.List;
 
-/** An exception thrown by an RPC client to indicate remote/server-side failure. */
-public final class RemoteException extends RuntimeException implements SafeLoggable {
+/**
+ * An exception thrown by an RPC client to indicate remote/server-side failure.
+ * <p>
+ * WARNING: Users should not subclass this exception.
+ * This class is not final to allow Conjure-Java to extend it and create custom RemoteExceptions.
+ * */
+public class RemoteException extends RuntimeException implements SafeLoggable {
     private static final long serialVersionUID = 1L;
     private static final String ERROR_INSTANCE_ID = "errorInstanceId";
     private static final String ERROR_CODE = "errorCode";
@@ -60,6 +65,11 @@ public RemoteException(SerializableError error, int status) {
                 SafeArg.of(ERROR_CODE, error.errorCode())));
     }
 
+    /**
+     * Returns a message that includes the error code, name, instance ID and parameters (if any).
+     * <p>
+     * This may contain sensitive information and should not be exposed to external callers.
+     */
     @Override
     public String getMessage() {
         // This field is not used in most environments so the cost of computation may be avoided.
@@ -89,11 +99,21 @@ private String renderUnsafeMessage() {
         return builder.toString();
     }
 
+    /**
+     * Returns a stable message for this exception that does not include parameters.
+     * <p>
+     * This message is safe to expose to external callers and will not expose sensitive information.
+     */
     @Override
     public String getLogMessage() {
         return stableMessage;
     }
 
+    /**
+     * Returns the safe arguments associated with this exception.
+     * <p>
+     * The arguments include the error instance ID, error name, and error code.
+     */
     @Override
     public List<Arg<?>> getArgs() {
         // RemoteException explicitly does not support arguments because they have already been recorded