Added an example of custom http header

example/exam/client/src/main/java/hprose/exam/client/ClientExam11.java

@@ -0,0 +1,38 @@
+package hprose.exam.client;
+
+import hprose.client.HproseHttpClient;
+import hprose.common.HproseContext;
+import hprose.common.HproseFilter;
+import java.nio.ByteBuffer;
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+
+class LogFilter implements HproseFilter {
+    private static final Logger logger = Logger.getLogger(LogFilter.class.getName());
+    @Override
+    public ByteBuffer inputFilter(ByteBuffer data, HproseContext context) {
+        logger.log(Level.INFO, context.get("httpHeader").toString());
+        return data;
+    }
+    @Override
+    public ByteBuffer outputFilter(ByteBuffer data, HproseContext context) {
+        Map<String, List<String>> header = new HashMap<>();
+        header.put("Test", Arrays.asList("Hello Hprose"));
+        context.set("httpHeader", header);
+        return data;
+    }
+}
+
+public class ClientExam11 {
+    public static void main(String[] args) throws Throwable {
+        HproseHttpClient client = new HproseHttpClient();
+        client.useService("http://localhost:8084/examserver/Methods");
+        client.addFilter(new LogFilter());
+        System.out.println(client.invoke("ex1_getId"));
+        System.out.println(client.invoke("ex2_getId"));
+    }
+}