Implement Record.toJson().

Author: blackwinter

build.gradle

@@ -34,6 +34,7 @@ subprojects {
     versions = [
       'ace':            '1.3.3',
       'equalsverifier': '3.8.2',
+      'jackson':        '2.13.3',
       'jetty':          '9.4.14.v20181114',
       'jquery':         '3.3.1-1',
       'junit_jupiter':  '5.8.2',

metafix/build.gradle

@@ -12,6 +12,7 @@ def passSystemProperties = {
 dependencies {
   implementation "org.eclipse.xtext:org.eclipse.xtext:${versions.xtext}"
   implementation "org.eclipse.xtext:org.eclipse.xtext.xbase:${versions.xtext}"
+  implementation "com.fasterxml.jackson.core:jackson-core:${versions.jackson}"
   implementation "com.google.guava:guava:${versions.guava}"
   implementation "org.slf4j:slf4j-api:${versions.slf4j}"
 

metafix/src/main/java/org/metafacture/metafix/Record.java

@@ -19,6 +19,14 @@
 import org.metafacture.metafix.FixPath.InsertMode;
 import org.metafacture.metafix.Value.TypeMatcher;
 
+import com.fasterxml.jackson.core.JsonFactory;
+import com.fasterxml.jackson.core.JsonGenerator;
+import com.fasterxml.jackson.core.SerializableString;
+import com.fasterxml.jackson.core.util.DefaultPrettyPrinter;
+
+import java.io.IOException;
+import java.io.StringWriter;
+import java.io.UncheckedIOException;
 import java.util.Collection;
 import java.util.Deque;
 import java.util.LinkedHashMap;
@@ -110,6 +118,27 @@ public String toString() {
         return super.toString();
     }
 
+    public String toJson() throws IOException {
+        return toJson(false);
+    }
+
+    public String toJson(final boolean prettyPrinting) throws IOException {
+        final StringWriter writer = new StringWriter();
+        final JsonGenerator jsonGenerator = new JsonFactory().createGenerator(writer);
+        jsonGenerator.setPrettyPrinter(prettyPrinting ? new DefaultPrettyPrinter((SerializableString) null) : null);
+
+        try {
+            toJson(jsonGenerator);
+        }
+        catch (final UncheckedIOException e) {
+            throw e.getCause();
+        }
+
+        jsonGenerator.flush();
+
+        return writer.toString();
+    }
+
     /**
      * Retrieves the field value from this record. Falls back to retrieving the
      * <i>virtual</i> field if the field name is not already

metafix/src/main/java/org/metafacture/metafix/Value.java

@@ -19,6 +19,10 @@
 import org.metafacture.commons.tries.SimpleRegexTrie;
 import org.metafacture.commons.tries.WildcardTrie;
 
+import com.fasterxml.jackson.core.JsonGenerator;
+
+import java.io.IOException;
+import java.io.UncheckedIOException;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.ConcurrentModificationException;
@@ -44,7 +48,7 @@
  * Represents a record value, i.e., either an {@link Array}, a {@link Hash},
  * or a {@link String}.
  */
-public class Value {
+public class Value { // checkstyle-disable-line ClassDataAbstractionCoupling
 
     private static final String FIELD_PATH_SEPARATOR = "\\.";
 
@@ -278,6 +282,31 @@ public String toString() {
         );
     }
 
+    private void toJson(final JsonGenerator jsonGenerator) {
+        if (isNull()) {
+            try {
+                jsonGenerator.writeNull();
+            }
+            catch (final IOException e) {
+                throw new UncheckedIOException(e);
+            }
+        }
+        else {
+            matchType()
+                .ifArray(a -> a.toJson(jsonGenerator))
+                .ifHash(h -> h.toJson(jsonGenerator))
+                .ifString(s -> {
+                    try {
+                        jsonGenerator.writeString(s);
+                    }
+                    catch (final IOException e) {
+                        throw new UncheckedIOException(e);
+                    }
+                })
+                .orElseThrow();
+        }
+    }
+
     /*package-private*/ static String[] split(final String fieldPath) {
         return fieldPath.split(FIELD_PATH_SEPARATOR);
     }
@@ -379,6 +408,8 @@ private abstract static class AbstractValueType {
         @Override
         public abstract String toString();
 
+        protected abstract void toJson(JsonGenerator jsonGenerator);
+
     }
 
     /**
@@ -448,6 +479,18 @@ public String toString() {
             return list.toString();
         }
 
+        @Override
+        protected void toJson(final JsonGenerator jsonGenerator) {
+            try {
+                jsonGenerator.writeStartArray();
+                forEach(v -> v.toJson(jsonGenerator));
+                jsonGenerator.writeEndArray();
+            }
+            catch (final IOException e) {
+                throw new UncheckedIOException(e);
+            }
+        }
+
         public void remove(final int index) {
             list.remove(index);
         }
@@ -712,6 +755,29 @@ public String toString() {
             return map.toString();
         }
 
+        @Override
+        protected void toJson(final JsonGenerator jsonGenerator) {
+            try {
+                jsonGenerator.writeStartObject();
+
+                forEach((f, v) -> {
+                    try {
+                        jsonGenerator.writeFieldName(f);
+                    }
+                    catch (final IOException e) {
+                        throw new UncheckedIOException(e);
+                    }
+
+                    v.toJson(jsonGenerator);
+                });
+
+                jsonGenerator.writeEndObject();
+            }
+            catch (final IOException e) {
+                throw new UncheckedIOException(e);
+            }
+        }
+
         /**
          * Avoids {@link ConcurrentModificationException} when modifying the hash based on matched fields.
          *