Update to specify the charset of response

In some Operational Systems (Like IBM Z/OS and IBM Z/Unix) the JRE runs with a charset different of UTF-8, those default charsets produce wrong behavior and truncated responses.

To avoid this kind of situations I put the specifc charset in the output writer.

This create a consistent response between different platforms.

Signed-off-by: João Paulo Binda Delboni <joaopdelboni@gmail.com>

Author: joaopdelboni

simpleclient_httpserver/src/main/java/io/prometheus/client/exporter/HTTPServer.java

@@ -9,6 +9,7 @@
 import java.net.HttpURLConnection;
 import java.net.InetSocketAddress;
 import java.net.URLDecoder;
+import java.nio.charset.Charset;
 import java.util.List;
 import java.util.Set;
 import java.util.HashSet;
@@ -61,7 +62,7 @@ public void handle(HttpExchange t) throws IOException {
             String contextPath = t.getHttpContext().getPath();
             ByteArrayOutputStream response = this.response.get();
             response.reset();
-            OutputStreamWriter osw = new OutputStreamWriter(response);
+            OutputStreamWriter osw = new OutputStreamWriter(response, Charset.forName("UTF-8"));
             if ("/-/healthy".equals(contextPath)) {
                 osw.write(HEALTHY_RESPONSE);
             } else {