#21 - Add JsonWriter unwrap() ... for example, gives access to the underlying Jackson JsonGenerator

Author: rbygrave

jsonb-jackson/src/main/java/io/avaje/jsonb/jackson/JacksonAdapter.java

@@ -64,6 +64,9 @@ public Builder failOnUnknown(boolean failOnUnknown) {
      * Build and return the JacksonAdapter.
      */
     public JacksonAdapter build() {
+      if (jsonFactory == null) {
+        jsonFactory = new JsonFactory();
+      }
       return new JacksonAdapter(serializeNulls, serializeEmpty, failOnUnknown, jsonFactory);
     }
   }

jsonb-jackson/src/main/java/io/avaje/jsonb/jackson/JacksonWriter.java

@@ -56,6 +56,12 @@ public void pretty(boolean pretty) {
     }
   }
 
+  @SuppressWarnings("unchecked")
+  @Override
+  public <T> T unwrap(Class<T> underlying) {
+    return (T) generator;
+  }
+
   @Override
   public void serializeNulls(boolean serializeNulls) {
     this.serializeNulls = serializeNulls;

jsonb-jackson/src/test/java/io/avaje/jsonb/jackson/UnwrapJacksonGeneratorTest.java

@@ -0,0 +1,63 @@
+package io.avaje.jsonb.jackson;
+
+import com.fasterxml.jackson.core.JsonGenerator;
+import com.fasterxml.jackson.core.JsonpCharacterEscapes;
+import com.fasterxml.jackson.core.SerializableString;
+import com.fasterxml.jackson.core.io.CharacterEscapes;
+import com.fasterxml.jackson.core.io.SerializedString;
+import io.avaje.jsonb.JsonWriter;
+import io.avaje.jsonb.Jsonb;
+import org.example.Address;
+import org.example.MyComponent;
+import org.junit.jupiter.api.Test;
+
+import java.io.StringWriter;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class UnwrapJacksonGeneratorTest {
+
+  @Test
+  void writer_unwrap() {
+    Jsonb jsonb = Jsonb.newBuilder()
+      .adapter(JacksonAdapter.newBuilder().build())
+      .add(new MyComponent())
+      .build();
+
+    StringWriter sw = new StringWriter();
+    try (JsonWriter writer = jsonb.writer(sw)) {
+      writer.unwrap(JsonGenerator.class).setCharacterEscapes(new HTMLCharacterEscapes());
+
+      Address withHtml = new Address().street("<p>my-html-content-with[&][\"][']</p>");
+      jsonb.toJson(withHtml, writer);
+    }
+    assertThat(sw.toString()).isEqualTo("{\"street\":\"&#60;p&#62;my-html-content-with[&#38;][&#34;][&#39;]&#60;/p&#62;\"}");
+  }
+
+  static class HTMLCharacterEscapes extends JsonpCharacterEscapes {
+
+    @Override
+    public int[] getEscapeCodesForAscii() {
+      int[] asciiEscapes = CharacterEscapes.standardAsciiEscapesForJSON();
+      // and force escaping of a few others:
+      asciiEscapes['<'] = CharacterEscapes.ESCAPE_CUSTOM;
+      asciiEscapes['>'] = CharacterEscapes.ESCAPE_CUSTOM;
+      asciiEscapes['&'] = CharacterEscapes.ESCAPE_CUSTOM;
+      asciiEscapes['"'] = CharacterEscapes.ESCAPE_CUSTOM;
+      asciiEscapes['\''] = CharacterEscapes.ESCAPE_CUSTOM;
+      return asciiEscapes;
+    }
+
+    @Override
+    public SerializableString getEscapeSequence(int ch) {
+      switch (ch) {
+        case '&' : return new SerializedString("&#38;");
+        case '<' : return new SerializedString("&#60;");
+        case '>' : return new SerializedString("&#62;");
+        case '\"' : return new SerializedString("&#34;");
+        case '\'' : return new SerializedString("&#39;");
+        default : return super.getEscapeSequence(ch);
+      }
+    }
+  }
+}

jsonb-jakarta/src/main/java/io/avaje/jsonb/jakarta/JakartaJsonWriter.java

@@ -25,6 +25,11 @@ final class JakartaJsonWriter implements JsonWriter {
     this.serializeEmpty = serializeEmpty;
   }
 
+  @Override
+  public <T> T unwrap(Class<T> underlying) {
+    throw new RuntimeException("Not implemented");
+  }
+
   @Override
   public void serializeNulls(boolean serializeNulls) {
     this.serializeNulls = serializeNulls;

jsonb/src/main/java/io/avaje/jsonb/JsonWriter.java

@@ -27,6 +27,30 @@
  */
 public interface JsonWriter extends Closeable, Flushable {
 
+  /**
+   * Unwrap the underlying generator being used.
+   * <p>
+   * We do this to get access to the underlying generator. For the case when
+   * using jackson-core we get access to Jackson JsonGenerator and can then
+   * do Jackson specific things like set custom escaping.
+   *
+   * <pre>{@code
+   *
+   *     try (JsonWriter writer = jsonb.writer(new StringWriter())) {
+   *
+   *       // get access to the underlying Jackson JsonGenerator
+   *       var generator = writer.unwrap(JsonGenerator.class)
+   *
+   *       // do Jackson specific things like ...
+   *       generator.setCharacterEscapes(new HTMLCharacterEscapes());
+   *
+   *       jsonb.toJson(myBean, writer);
+   *     }
+   *
+   * }</pre>
+   */
+  <T> T unwrap(Class<T> underlying);
+
   /**
    * Set to serialise null values or not.
    */

jsonb/src/main/java/io/avaje/jsonb/Jsonb.java

@@ -127,6 +127,13 @@ static Builder newBuilder() {
    */
   void toJson(Object any, OutputStream outputStream);
 
+  /**
+   * Write to the given writer.
+   * <p>
+   * This is a convenience method for {@code jsonb.type(Object.class).toJson(any, writer) }
+   */
+  void toJson(Object any, JsonWriter jsonWriter);
+
   /**
    * Return the JsonType used to read and write json for the given class.
    *

jsonb/src/main/java/io/avaje/jsonb/core/DJsonb.java

@@ -66,6 +66,11 @@ public void toJson(Object any, OutputStream outputStream) {
     anyType.toJson(any, outputStream);
   }
 
+  @Override
+  public void toJson(Object any, JsonWriter jsonWriter) {
+    anyType.toJson(any, jsonWriter);
+  }
+
   @Override
   public PropertyNames properties(String... names) {
     return io.properties(names);

jsonb/src/main/java/io/avaje/jsonb/spi/DelegateJsonWriter.java

@@ -16,6 +16,11 @@ public DelegateJsonWriter(JsonWriter delegate) {
     this.delegate = delegate;
   }
 
+  @Override
+  public <T> T unwrap(Class<T> underlying) {
+    return delegate.unwrap(underlying);
+  }
+
   @Override
   public final void serializeNulls(boolean serializeNulls) {
     delegate.serializeNulls(serializeNulls);

jsonb/src/main/java/io/avaje/jsonb/stream/JsonWriteAdapter.java

@@ -25,6 +25,12 @@ final class JsonWriteAdapter implements JsonWriter {
     this.serializeEmpty = serializeEmpty;
   }
 
+  @SuppressWarnings("unchecked")
+  @Override
+  public <T> T unwrap(Class<T> underlying) {
+    return (T)generator;
+  }
+
   @Override
   public void close() {
     generator.close();