add hessian stream API (#5780)

diff --git a/dubbo-serialization/dubbo-serialization-hessian2/src/main/java/org/apache/dubbo/common/serialize/hessian2/Hessian2ObjectInput.java b/dubbo-serialization/dubbo-serialization-hessian2/src/main/java/org/apache/dubbo/common/serialize/hessian2/Hessian2ObjectInput.java
index d1ef214..08c758d 100644
--- a/dubbo-serialization/dubbo-serialization-hessian2/src/main/java/org/apache/dubbo/common/serialize/hessian2/Hessian2ObjectInput.java
+++ b/dubbo-serialization/dubbo-serialization-hessian2/src/main/java/org/apache/dubbo/common/serialize/hessian2/Hessian2ObjectInput.java
@@ -97,4 +97,7 @@
         return readObject(cls);
     }
 
+    public InputStream readInputStream() throws IOException {
+        return mH2i.readInputStream();
+    }
 }
diff --git a/dubbo-serialization/dubbo-serialization-hessian2/src/main/java/org/apache/dubbo/common/serialize/hessian2/Hessian2ObjectOutput.java b/dubbo-serialization/dubbo-serialization-hessian2/src/main/java/org/apache/dubbo/common/serialize/hessian2/Hessian2ObjectOutput.java
index 38fd3db..61e38c0 100644
--- a/dubbo-serialization/dubbo-serialization-hessian2/src/main/java/org/apache/dubbo/common/serialize/hessian2/Hessian2ObjectOutput.java
+++ b/dubbo-serialization/dubbo-serialization-hessian2/src/main/java/org/apache/dubbo/common/serialize/hessian2/Hessian2ObjectOutput.java
@@ -93,4 +93,8 @@
     public void flushBuffer() throws IOException {
         mH2o.flushBuffer();
     }
+
+    public OutputStream getOutputStream() throws IOException {
+        return mH2o.getBytesOutputStream();
+    }
 }