add field case casing support for JsonBuilder

.idea/dictionaries/kimchy.xml

@@ -8,6 +8,7 @@
       <w>birthdate</w>
       <w>bool</w>
       <w>booleans</w>
+      <w>camelcase</w>
       <w>checksum</w>
       <w>closeable</w>
       <w>commitable</w>

modules/elasticsearch/src/main/java/org/elasticsearch/util/json/BinaryJsonBuilder.java

@@ -42,7 +42,9 @@ public class BinaryJsonBuilder extends JsonBuilder<BinaryJsonBuilder> {
         private static final ThreadLocal<ThreadLocals.CleanableValue<BinaryJsonBuilder>> cache = new ThreadLocal<ThreadLocals.CleanableValue<BinaryJsonBuilder>>() {
             @Override protected ThreadLocals.CleanableValue<BinaryJsonBuilder> initialValue() {
                 try {
-                    return new ThreadLocals.CleanableValue<BinaryJsonBuilder>(new BinaryJsonBuilder());
+                    BinaryJsonBuilder builder = new BinaryJsonBuilder();
+                    builder.cachedStringBuilder = new StringBuilder();
+                    return new ThreadLocals.CleanableValue<BinaryJsonBuilder>(builder);
                 } catch (IOException e) {
                     throw new ElasticSearchException("Failed to create json generator", e);
                 }
@@ -63,6 +65,8 @@ public class BinaryJsonBuilder extends JsonBuilder<BinaryJsonBuilder> {
 
     private final JsonFactory factory;
 
+    private StringBuilder cachedStringBuilder;
+
     public BinaryJsonBuilder() throws IOException {
         this(Jackson.defaultJsonFactory());
     }
@@ -81,6 +85,10 @@ public class BinaryJsonBuilder extends JsonBuilder<BinaryJsonBuilder> {
         this.builder = this;
     }
 
+    @Override protected StringBuilder cachedStringBuilder() {
+        return cachedStringBuilder;
+    }
+
     @Override public BinaryJsonBuilder raw(byte[] json) throws IOException {
         flush();
         bos.write(json);
@@ -88,6 +96,7 @@ public class BinaryJsonBuilder extends JsonBuilder<BinaryJsonBuilder> {
     }
 
     @Override public BinaryJsonBuilder reset() throws IOException {
+        fieldCaseConversion = globalFieldCaseConversion;
         bos.reset();
         generator = factory.createJsonGenerator(bos, JsonEncoding.UTF8);
         return this;

modules/elasticsearch/src/main/java/org/elasticsearch/util/json/JsonBuilder.java

@@ -19,6 +19,7 @@
 
 package org.elasticsearch.util.json;
 
+import org.elasticsearch.util.Strings;
 import org.elasticsearch.util.concurrent.NotThreadSafe;
 import org.joda.time.DateTimeZone;
 import org.joda.time.ReadableInstant;
@@ -39,12 +40,35 @@ import java.util.Date;
 @NotThreadSafe
 public abstract class JsonBuilder<T extends JsonBuilder> {
 
+    public static enum FieldCaseConversion {
+        /**
+         * No came conversion will occur.
+         */
+        NONE,
+        /**
+         * Camel Case will be converted to Underscore casing.
+         */
+        UNDERSCORE,
+        /**
+         * Underscore will be converted to Camel case conversion.
+         */
+        CAMELCASE
+    }
+
     private final static DateTimeFormatter defaultDatePrinter = ISODateTimeFormat.dateTime().withZone(DateTimeZone.UTC);
 
+    protected static FieldCaseConversion globalFieldCaseConversion = FieldCaseConversion.CAMELCASE;
+
+    public static void globalFieldCaseConversion(FieldCaseConversion globalFieldCaseConversion) {
+        JsonBuilder.globalFieldCaseConversion = globalFieldCaseConversion;
+    }
+
     protected org.codehaus.jackson.JsonGenerator generator;
 
     protected T builder;
 
+    protected FieldCaseConversion fieldCaseConversion = globalFieldCaseConversion;
+
     public static StringJsonBuilder stringJsonBuilder() throws IOException {
         return StringJsonBuilder.Cached.cached();
     }
@@ -57,6 +81,11 @@ public abstract class JsonBuilder<T extends JsonBuilder> {
         return BinaryJsonBuilder.Cached.cached();
     }
 
+    public T fieldCaseConversion(FieldCaseConversion fieldCaseConversion) {
+        this.fieldCaseConversion = fieldCaseConversion;
+        return builder;
+    }
+
     public T prettyPrint() {
         generator.useDefaultPrettyPrinter();
         return builder;
@@ -113,6 +142,11 @@ public abstract class JsonBuilder<T extends JsonBuilder> {
     }
 
     public T field(String name) throws IOException {
+        if (fieldCaseConversion == FieldCaseConversion.UNDERSCORE) {
+            name = Strings.toUnderscoreCase(name);
+        } else if (fieldCaseConversion == FieldCaseConversion.CAMELCASE) {
+            name = Strings.toCamelCase(name);
+        }
         generator.writeFieldName(name);
         return builder;
     }
@@ -369,6 +403,10 @@ public abstract class JsonBuilder<T extends JsonBuilder> {
 
     public abstract String string() throws IOException;
 
+    protected StringBuilder cachedStringBuilder() {
+        return null;
+    }
+
     public void close() {
         try {
             generator.close();

modules/elasticsearch/src/main/java/org/elasticsearch/util/json/StringJsonBuilder.java

@@ -44,7 +44,9 @@ public class StringJsonBuilder extends JsonBuilder<StringJsonBuilder> {
         private static final ThreadLocal<ThreadLocals.CleanableValue<StringJsonBuilder>> cache = new ThreadLocal<ThreadLocals.CleanableValue<StringJsonBuilder>>() {
             @Override protected ThreadLocals.CleanableValue<StringJsonBuilder> initialValue() {
                 try {
-                    return new ThreadLocals.CleanableValue<StringJsonBuilder>(new StringJsonBuilder());
+                    StringJsonBuilder builder = new StringJsonBuilder();
+                    builder.cachedStringBuilder = new StringBuilder();
+                    return new ThreadLocals.CleanableValue<StringJsonBuilder>(builder);
                 } catch (IOException e) {
                     throw new ElasticSearchException("Failed to create json generator", e);
                 }
@@ -67,6 +69,8 @@ public class StringJsonBuilder extends JsonBuilder<StringJsonBuilder> {
 
     final UnicodeUtil.UTF8Result utf8Result = new UnicodeUtil.UTF8Result();
 
+    private StringBuilder cachedStringBuilder;
+
     public StringJsonBuilder() throws IOException {
         this(Jackson.defaultJsonFactory());
     }
@@ -85,6 +89,10 @@ public class StringJsonBuilder extends JsonBuilder<StringJsonBuilder> {
         this.builder = this;
     }
 
+    @Override protected StringBuilder cachedStringBuilder() {
+        return cachedStringBuilder;
+    }
+
     @Override public StringJsonBuilder raw(byte[] json) throws IOException {
         flush();
         Unicode.UTF16Result result = Unicode.unsafeFromBytesAsUtf16(json);
@@ -93,6 +101,7 @@ public class StringJsonBuilder extends JsonBuilder<StringJsonBuilder> {
     }
 
     public StringJsonBuilder reset() throws IOException {
+        fieldCaseConversion = globalFieldCaseConversion;
         writer.reset();
         generator = factory.createJsonGenerator(writer);
         return this;

modules/elasticsearch/src/test/java/org/elasticsearch/util/json/JsonBuilderTests.java

@@ -33,6 +33,7 @@ import java.util.Date;
 import java.util.Map;
 
 import static org.elasticsearch.util.json.Jackson.*;
+import static org.elasticsearch.util.json.JsonBuilder.FieldCaseConversion.*;
 import static org.hamcrest.MatcherAssert.*;
 import static org.hamcrest.Matchers.*;
 
@@ -100,4 +101,14 @@ public class JsonBuilderTests {
                 .map();
         System.out.println("Data: " + defaultObjectMapper().writeValueAsString(data));
     }
+
+    @Test public void testFieldCaseConversion() throws Exception {
+        StringJsonBuilder builder = JsonBuilder.stringJsonBuilder().fieldCaseConversion(CAMELCASE);
+        builder.startObject().field("test_name", "value").endObject();
+        assertThat(builder.string(), equalTo("{\"testName\":\"value\"}"));
+
+        builder = JsonBuilder.stringJsonBuilder().fieldCaseConversion(UNDERSCORE);
+        builder.startObject().field("testName", "value").endObject();
+        assertThat(builder.string(), equalTo("{\"test_name\":\"value\"}"));
+    }
 }