Set characterEncoding for the HttpServletResponse of the SingleQueryResponseWriter

graphql-java-servlet/src/main/java/graphql/kickstart/servlet/SingleQueryResponseWriter.java

@@ -2,11 +2,12 @@
 
 import graphql.ExecutionResult;
 import graphql.kickstart.execution.GraphQLObjectMapper;
+import lombok.RequiredArgsConstructor;
+
 import java.io.IOException;
 import java.nio.charset.StandardCharsets;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
-import lombok.RequiredArgsConstructor;
 
 @RequiredArgsConstructor
 class SingleQueryResponseWriter implements QueryResponseWriter {
@@ -18,6 +19,7 @@ class SingleQueryResponseWriter implements QueryResponseWriter {
   public void write(HttpServletRequest request, HttpServletResponse response) throws IOException {
     response.setContentType(HttpRequestHandler.APPLICATION_JSON_UTF8);
     response.setStatus(HttpRequestHandler.STATUS_OK);
+    response.setCharacterEncoding(StandardCharsets.UTF_8.name());
     String responseContent = graphQLObjectMapper.serializeResultAsJson(result);
     response.setContentLength(responseContent.getBytes(StandardCharsets.UTF_8).length);
     response.getWriter().write(responseContent);

graphql-java-servlet/src/test/groovy/graphql/kickstart/servlet/SingleQueryResponseWriterTest.groovy

@@ -0,0 +1,40 @@
+package graphql.kickstart.servlet
+
+import com.fasterxml.jackson.databind.ObjectMapper
+import graphql.ExecutionResultImpl
+import graphql.kickstart.execution.GraphQLObjectMapper
+import org.codehaus.groovy.runtime.StringBufferWriter
+import spock.lang.Specification
+import spock.lang.Unroll
+
+import javax.servlet.http.HttpServletRequest
+import javax.servlet.http.HttpServletResponse
+
+class SingleQueryResponseWriterTest extends Specification {
+
+  @Unroll
+  def "should write utf8 results into the response with content #result"() {
+    given:
+      def graphQLObjectMapperMock = GraphQLObjectMapper.newBuilder().withObjectMapperProvider({ new ObjectMapper() }).build()
+      graphQLObjectMapperMock.getJacksonMapper() >> new ObjectMapper()
+
+      def requestMock = Mock(HttpServletRequest)
+      def responseMock = Mock(HttpServletResponse)
+
+      def responseContentBuffer = new StringBuffer()
+      responseMock.getWriter() >> new PrintWriter(new StringBufferWriter(responseContentBuffer))
+      1 * responseMock.setContentLength(expectedContentLenght)
+      1 * responseMock.setCharacterEncoding("UTF-8")
+
+    expect:
+      def writer = new SingleQueryResponseWriter(new ExecutionResultImpl(result, []), graphQLObjectMapperMock)
+      writer.write(requestMock, responseMock)
+
+      responseContentBuffer.toString() == expectedResponseContent
+
+    where:
+      result                || expectedContentLenght | expectedResponseContent
+      [testValue: "abcde"]  || 30                    | """{"data":{"testValue":"abcde"}}"""
+      [testValue: "äöüüöß"] || 37                    | """{"data":{"testValue":"äöüüöß"}}"""
+  }
+}