OutputStreamTaskListener.Default for convenience

src/main/java/org/jenkinsci/plugins/workflow/log/BufferedBuildListener.java

@@ -24,8 +24,6 @@
 
 package org.jenkinsci.plugins.workflow.log;
 
-import edu.umd.cs.findbugs.annotations.NonNull;
-import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
 import hudson.CloseProofOutputStream;
 import hudson.model.BuildListener;
 import hudson.remoting.Channel;
@@ -37,38 +35,29 @@
 import java.io.IOException;
 import java.io.OutputStream;
 import java.io.PrintStream;
-import java.nio.charset.StandardCharsets;
 import java.util.logging.Logger;
 import org.jenkinsci.remoting.SerializableOnlyOverRemoting;
 
 /**
  * Unlike {@link StreamTaskListener} this does not set {@code autoflush} on the reconstructed {@link PrintStream}.
  * It also wraps on the remote side in {@link DelayBufferedOutputStream}.
  */
-final class BufferedBuildListener implements BuildListener, Closeable, SerializableOnlyOverRemoting, OutputStreamTaskListener {
+final class BufferedBuildListener extends OutputStreamTaskListener.Default implements BuildListener, Closeable, SerializableOnlyOverRemoting {
 
     private static final Logger LOGGER = Logger.getLogger(BufferedBuildListener.class.getName());
 
     private final OutputStream out;
-    @SuppressFBWarnings(value = "SE_BAD_FIELD", justification = "using Replacement anyway, fields here are irrelevant")
-    private final PrintStream ps;
 
     BufferedBuildListener(OutputStream out) {
         this.out = out;
-        ps = new PrintStream(out, false, StandardCharsets.UTF_8);
     }
 
     @Override public OutputStream getOutputStream() {
         return out;
     }
 
-    @NonNull
-    @Override public PrintStream getLogger() {
-        return ps;
-    }
-
     @Override public void close() throws IOException {
-        ps.close();
+        getLogger().close();
     }
 
     private Object writeReplace() {

src/main/java/org/jenkinsci/plugins/workflow/log/OutputStreamTaskListener.java

@@ -42,9 +42,6 @@
  * {@link TaskListener} which can directly return an {@link OutputStream} not wrapped in a {@link PrintStream}.
  * This is important for logging since the error-swallowing behavior of {@link PrintStream} is unwanted,
  * and {@link PrintStream#checkError} is useless.
- * <p>{@link #getLogger} should generally be implemented in terms of {@link #getOutputStream}
- * (no autoflush, using {@link StandardCharsets#UTF_8})
- * but there is not a {@code default} implementation since the result should be cached in a field.
  */
 @Restricted(Beta.class)
 public interface OutputStreamTaskListener extends TaskListener {
@@ -97,4 +94,20 @@ public interface OutputStreamTaskListener extends TaskListener {
         return os;
     }
 
+    /**
+     * Convenience implementation handling {@link #getLogger}.
+     */
+    abstract class Default implements OutputStreamTaskListener {
+
+        private transient PrintStream ps;
+
+        @Override public synchronized PrintStream getLogger() {
+            if (ps == null) {
+                ps = new PrintStream(getOutputStream(), false, StandardCharsets.UTF_8);
+            }
+            return ps;
+        }
+
+    }
+
 }

src/main/java/org/jenkinsci/plugins/workflow/log/TaskListenerDecorator.java

@@ -236,7 +236,7 @@ private static OutputStream decorateAll(OutputStream base, List<TaskListenerDeco
         return base;
     }
 
-    private static final class DecoratedTaskListener implements BuildListener, OutputStreamTaskListener {
+    private static final class DecoratedTaskListener extends OutputStreamTaskListener.Default implements BuildListener {
 
         private static final long serialVersionUID = 1;
 
@@ -253,7 +253,6 @@ private static final class DecoratedTaskListener implements BuildListener, Outpu
         private final @NonNull List<TaskListenerDecorator> decorators;
 
         private transient OutputStream out;
-        private transient PrintStream logger;
 
         DecoratedTaskListener(@NonNull TaskListener delegate, @NonNull List<TaskListenerDecorator> decorators) {
             this.delegate = delegate;
@@ -270,14 +269,6 @@ private static final class DecoratedTaskListener implements BuildListener, Outpu
             return out;
         }
 
-        @NonNull
-        @Override public PrintStream getLogger() {
-            if (logger == null) {
-                logger = new PrintStream(getOutputStream(), false, StandardCharsets.UTF_8);
-            }
-            return logger;
-        }
-
         @Override public String toString() {
             return "DecoratedTaskListener[" + delegate + decorators + "]";
         }