Some changes past #1051; add tests, release notes

Author: cowtowncoder

release-notes/CREDITS-2.x

@@ -56,6 +56,8 @@ Aaron Digulla:
  * Contributed #1042: Allow configuring spaces before and/or after the colon in
    `DefaultPrettyPrinter`
   (2.16.0)
+ * Contributed #1051: Add `JsonGeneratorDecorator` to allow decorating `JsonGenerator`s
+  (2.16.0)
 
 Derek Clarkson (drekka@github)
   * Reported #184: WRITE_NUMBERS_AS_STRINGS disables WRITE_BIGDECIMAL_AS_PLAIN

release-notes/VERSION-2.x

@@ -33,6 +33,8 @@ a pure JSON library.
  (contributed by @digulla)
 #1050: Compare `_snapshotInfo` in `Version`
  (contributed by @artoonie)
+#1051: Add `JsonGeneratorDecorator` to allow decorating `JsonGenerator`s
+ (contributed by @digulla)
 
 2.15.2 (30-May-2023)
 

src/main/java/com/fasterxml/jackson/core/JsonFactory.java

@@ -22,6 +22,7 @@
 import com.fasterxml.jackson.core.util.BufferRecycler;
 import com.fasterxml.jackson.core.util.BufferRecyclers;
 import com.fasterxml.jackson.core.util.JacksonFeature;
+import com.fasterxml.jackson.core.util.JsonGeneratorDecorator;
 import com.fasterxml.jackson.core.util.Separators;
 
 /**
@@ -293,6 +294,14 @@ public static int collectDefaults() {
      */
     protected OutputDecorator _outputDecorator;
 
+    /**
+     * List of {@link JsonGeneratorDecorator}s to apply to {@link JsonGenerator}s
+     * after construction; applied in the order of addition.
+     *
+     * @since 2.16
+     */
+    protected final List<JsonGeneratorDecorator> _generatorDecorators;
+    
     /**
      * Separator used between root-level values, if any; null indicates
      * "do not add separator".
@@ -319,9 +328,6 @@ public static int collectDefaults() {
      */
     protected final char _quoteChar;
 
-    /** @since 2.16 */
-    protected List<JsonGeneratorDecorator> _generatorDecorators = new ArrayList<>();
-
     /*
     /**********************************************************
     /* Construction
@@ -344,6 +350,7 @@ public JsonFactory(ObjectCodec oc) {
         _objectCodec = oc;
         _quoteChar = DEFAULT_QUOTE_CHAR;
         _streamReadConstraints = StreamReadConstraints.defaults();
+        _generatorDecorators = null;
     }
 
     /**
@@ -364,6 +371,7 @@ protected JsonFactory(JsonFactory src, ObjectCodec codec)
         _generatorFeatures = src._generatorFeatures;
         _inputDecorator = src._inputDecorator;
         _outputDecorator = src._outputDecorator;
+        _generatorDecorators = _copy(src._generatorDecorators);
         _streamReadConstraints = src._streamReadConstraints == null ?
             StreamReadConstraints.defaults() : src._streamReadConstraints;
 
@@ -390,6 +398,7 @@ public JsonFactory(JsonFactoryBuilder b) {
         _generatorFeatures = b._streamWriteFeatures;
         _inputDecorator = b._inputDecorator;
         _outputDecorator = b._outputDecorator;
+        _generatorDecorators = _copy(b._generatorDecorators);
         _streamReadConstraints = b._streamReadConstraints == null ?
                 StreamReadConstraints.defaults() : b._streamReadConstraints;
 
@@ -398,7 +407,6 @@ public JsonFactory(JsonFactoryBuilder b) {
         _rootValueSeparator = b._rootValueSeparator;
         _maximumNonEscapedChar = b._maximumNonEscapedChar;
         _quoteChar = b._quoteChar;
-        _generatorDecorators = new ArrayList<>(b._generatorDecorators);
     }
 
     /**
@@ -417,6 +425,7 @@ protected JsonFactory(TSFBuilder<?,?> b, boolean bogus) {
         _generatorFeatures = b._streamWriteFeatures;
         _inputDecorator = b._inputDecorator;
         _outputDecorator = b._outputDecorator;
+        _generatorDecorators = _copy(b._generatorDecorators);
         _streamReadConstraints = b._streamReadConstraints == null ?
                 StreamReadConstraints.defaults() : b._streamReadConstraints;
 
@@ -487,6 +496,14 @@ protected void _checkInvalidCopy(Class<?> exp)
         }
     }
 
+    // @since 2.16
+    protected static <T> List<T> _copy(List<T> src) {
+        if (src == null) {
+            return src;
+        }
+        return new ArrayList<T>(src);
+    }
+
     /*
     /**********************************************************
     /* Serializable overrides
@@ -1901,13 +1918,6 @@ protected JsonGenerator _createGenerator(Writer out, IOContext ctxt) throws IOEx
         return _decorate(gen);
     }
 
-    private JsonGenerator _decorate(JsonGenerator result) {
-        for(JsonGeneratorDecorator decorator : _generatorDecorators) {
-            result = decorator.decorate(this, result);
-        }
-        return result;
-    }
-
     /**
      * Overridable factory method that actually instantiates generator for
      * given {@link OutputStream} and context object, using UTF-8 encoding.
@@ -2008,6 +2018,25 @@ protected final Writer _decorate(Writer out, IOContext ctxt) throws IOException
         return out;
     }
 
+    /**
+     * Helper method for applying all registered {@link JsonGeneratorDecorator}s
+     * on freshly constructed {@link JsonGenerator}.
+     *
+     * @param g Generator constructed that is to be decorated
+     *
+     * @return Generator after applying all registered {@link JsonGeneratorDecorator}s.
+     *
+     * @since 2.16
+     */
+    protected JsonGenerator _decorate(JsonGenerator g) {
+        if (_generatorDecorators != null) {
+            for (JsonGeneratorDecorator decorator : _generatorDecorators) {
+                g = decorator.decorate(this, g);
+            }
+        }
+        return g;
+    }
+
     /*
     /**********************************************************
     /* Internal factory methods, other

src/main/java/com/fasterxml/jackson/core/TSFBuilder.java

@@ -7,6 +7,7 @@
 import com.fasterxml.jackson.core.io.OutputDecorator;
 import com.fasterxml.jackson.core.json.JsonReadFeature;
 import com.fasterxml.jackson.core.json.JsonWriteFeature;
+import com.fasterxml.jackson.core.util.JsonGeneratorDecorator;
 
 /**
  * Since 2.10, Builder class is offered for creating token stream factories
@@ -87,8 +88,10 @@ public abstract class TSFBuilder<F extends JsonFactory,
      */
     protected StreamReadConstraints _streamReadConstraints;
 
-    /** @since 2.16 */
-    protected List<JsonGeneratorDecorator> _generatorDecorators = new ArrayList<>();
+    /**
+     * @since 2.16
+     */
+    protected List<JsonGeneratorDecorator> _generatorDecorators;
 
     /*
     /**********************************************************************
@@ -291,6 +294,9 @@ public B streamReadConstraints(StreamReadConstraints streamReadConstraints) {
     // // // Other methods
 
     public B decorateWith(JsonGeneratorDecorator decorator) {
+        if (_generatorDecorators == null) {
+            _generatorDecorators = new ArrayList<>();
+        }
         _generatorDecorators.add(decorator);
         return _this();
     }

src/main/java/com/fasterxml/jackson/core/JsonGeneratorDecorator.java renamed to src/main/java/com/fasterxml/jackson/core/util/JsonGeneratorDecorator.java

@@ -1,6 +1,15 @@
-package com.fasterxml.jackson.core;
+package com.fasterxml.jackson.core.util;
 
-public interface JsonGeneratorDecorator {
+import com.fasterxml.jackson.core.JsonFactory;
+import com.fasterxml.jackson.core.JsonGenerator;
+
+/**
+ * Simple interface to allow adding decorators around {@link JsonGenerator}s.
+ *
+ * @since 2.16
+ */
+public interface JsonGeneratorDecorator
+{
     /**
      * Allow to decorate {@link JsonGenerator} instances returned by {@link JsonFactory}.
      * 

src/test/java/com/fasterxml/jackson/core/json/TestDecorators.java

@@ -6,6 +6,8 @@
 import com.fasterxml.jackson.core.io.IOContext;
 import com.fasterxml.jackson.core.io.InputDecorator;
 import com.fasterxml.jackson.core.io.OutputDecorator;
+import com.fasterxml.jackson.core.util.JsonGeneratorDecorator;
+import com.fasterxml.jackson.core.util.JsonGeneratorDelegate;
 
 /**
  * Unit tests to verify that input and output decorators work as
@@ -63,9 +65,28 @@ public Writer decorate(IOContext ctxt, Writer w) throws IOException
         }
     }
 
+    static class SimpleGeneratorDecorator implements JsonGeneratorDecorator
+    {
+        @Override
+        public JsonGenerator decorate(JsonFactory factory, JsonGenerator generator) {
+            return new TextHider(generator);
+        }
+
+        static class TextHider extends JsonGeneratorDelegate {
+            public TextHider(JsonGenerator g) {
+                super(g);
+            }
+
+            @Override
+            public void writeString(String text) throws IOException {
+                delegate.writeString("***");
+            }
+        }
+    }
+    
     /*
     /**********************************************************
-    /* Unit tests
+    /* Unit tests: input/output decoration
     /**********************************************************
      */
 
@@ -142,4 +163,34 @@ public void testDeprecatedMethods() throws IOException
         f.setOutputDecorator(outDec);
         assertSame(outDec, f.getOutputDecorator());
     }
+
+    /*
+    /**********************************************************
+    /* Unit tests: input/output decoration
+    /**********************************************************
+     */
+
+    public void testGeneratorDecoration() throws IOException
+    {
+        JsonFactory f = JsonFactory.builder()
+                .decorateWith(new SimpleGeneratorDecorator())
+                .build();
+
+        StringWriter sw = new StringWriter();
+        try (JsonGenerator g = f.createGenerator(sw)) {
+            g.writeStartObject();
+            g.writeStringField("password", "s3cr37!!!");
+            g.writeEndObject();
+        }
+        assertEquals(a2q("{'password':'***'}"), sw.toString());
+
+        ByteArrayOutputStream bytes = new ByteArrayOutputStream();
+        try (JsonGenerator g = f.createGenerator(bytes)) {
+            g.writeStartObject();
+            g.writeStringField("password", "s3cr37x!!");
+            g.writeEndObject();
+        }
+        assertEquals(a2q("{'password':'***'}"), utf8String(bytes));
+    }
+
 }