Develop Reference

Sending java object to python and receive it back

Consider an object in java which implements Serializable. I want to send that object to a python code on TCP socket. I am serializing object and sending on TCP by using :
//socket connection code
PySessionObject object = new PySessionObject();
object.setMethodCall(PyServerMethodConstant.SETATTRIBUTE);
object.setAttributeName(name);
object.setAttributeValue(value);// value is of object type which also implements Serializable
os = sChannel.socket().getOutputStream();
oos = new ObjectOutputStream(os);
oos.writeObject(object);
oos.flush();
os.flush();
//socket closing and exception handling
Now I want to convert this byte stream into object in python perform some operation on that object and send it back to java world and deserialize it again. For this purpose I come to about javaobj-py3, with this everything is fine until I pass LinkedHashMap in setAttributeValue(). In Python I am doing this:
total_data=b''
while True:
data = self.clientsocket.recv(8192)
if not data: break
total_data += data
pyobj = javaobj.loads(total_data)
For this I am getting exception as:
RuntimeError: Unknown OpCode in the stream: 0x8 (at offset 0x14C)
What will be cause? Is it like opcodes are not found for "something"? Is anyone can suggest any other idea to convert byte stream send from java into object in python world perform some operation on that object and send it back to java world and deserialize it again.

You can convert the object to a JSON string and then send over the wire.
To convert object to json
new GSONBuilder().create().toJSON(obj);
To convert json to object
new GSONBuilder().create().fromJSON(jsonString, YouObject.class);
I prefer using GSON for converting a object to json and reverse in java. In python you can use json library. The methods are
json.loads(string) and json.dumps(object)

Reading a binary file from the file system as a BLOB to use in rhino with javascript

I'm planing to use SheetJS with rhino. And sheetjs takes a binary object(BLOB if i'm correct) as it's input. So i need to read a file from the system using stranded java I/O methods and store it into a blob before passing it to sheetjs. eg :-
var XLDataWorkBook = XLSX.read(blobInput, {type : "binary"});
So how can i create a BLOB(or appropriate type) from a binary file in java in order to pass it in.
i guess i cant pass streams because i guess XLSX needs a completely created object to process.

I found the answer to this by myself. i was able to get it done this way.
Read the file with InputStream and then write it to a ByteArrayOutputStream. like below.
ByteArrayOutputStream buffer = new ByteArrayOutputStream();
...
buffer.write(bytes, 0, len);
Then create a byte array from it.
byte[] byteArray = buffer.toByteArray();
Finally i did convert it to a Base64 String (which is also applicable in my case) using the "Base64.encodeBase64String()" method in apache.commons.codec.binary package. So i can pass Base64 String as a method parameter.
If you further need there are lot of libraries(3rd-party and default) available for Base64 to Blob conversion as well.

How to Serialize/Deserialize an object without implementing Serializable interface?

If a mail is send to my inbox, I recieve a message, and I'm inserting the contents into DB.
I have a org.springframework.integration.core.Message something like follows:
public void receive(Message<?> message)
{
//I am inserting message contents into DB
}
Now in the event of failure, I wanted to have fail safe recovery mechanism, what I am thinking is to serialize the Message object into a file and later deserialize and update to DB.
Question
1. In this situation how to serialize the Message object?
2. Other than serialization any other mechanism that can be used?
EDIT
I have not done Serialization before, I heard like the class should implements Serializable in order to use ObjectOutputStream, in this case I don't want to create a subclass of Message, So how to serialize Message to File?

Sure, there are many serialization mechanisms apart from the jvm one.
XML
JSON
BSON
MessagePack
protobufs
...
Some of them are text-based, some are binary. All have drawbacks and pluses. Text-based ones are human-readable, binary ones are faster and take up less space.
There are java libraries that handle all the above formats: JAXB (XML), Jackson (JSON), etc.

In this situation how to serialize the Message object? Other than serialization any other mechanism that can be used?
Extract all the data you need from the Message and save it. You can do this in any manner you choose.
You can deserialize it by populating a new Message with the data you saved.

I don't know if I probably understood it al right.. but assuming Message is not much more than lots of strings and some integers you can just use directly an ObjectOutputStream and write it to a file (binary) and then readin later. Why not?
Message e = new Message();
ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("whatever");
oos.writeObject(message);
// read in
ObjectInputStream ois = new ObjectInputStream(new FileInputStream("whatever");
Message e = (Message) ois.readObject();

Java object from JSON input file

Hi I have a json input file as follows,
{'Latitude':'20',
'coolness':2.0,
'altitude':39000,
'pilot':{'firstName':'Buzz',
'lastName':'Aldrin'},
'mission':'apollo 11'}
How to create a java object from the json input file.
Thanks

You can use the very simple GSON library, with the Gson#fromJson() method.
Here's an example: Converting JSON to Java

There are more than one APIs that can be used. The simplest one is JSONObject
Just do the following:
JSONObject o = new JSONObject(jsonString);
int alt = o.getInt("altitude");
....
there are getXXX methods for each type. It basically stores the object as a map. This is a slow API.
You may use Google's Gson, which is an elegant and better library -- slightly more work required than JSONObject. If you are really concerned about speed, use Jackson.

groovy soapUI deserialize

Just started using soapUI and I like it a lot.
In a particular case using REST, I'm receiving serialized object.
I would like :
to retrieve the serialized byte array and transform it into a Java object
re-transform the java object into an XML response (using JAXB)
so it can be human readable.
Is this feasible?

Be sure to consider using XML serialization (e.g. XStream) instead of binary one to avoid version compatibility problems before using the next solution:
Import your Java class to SoapUI groovy script (as described there) or re-define your Java class in Groovy code with Serializable interface implemented:
class Person implements Serializable { String name; int age }
Use ObjectInputStream and classLoader to load deserialize objects into object:
// use your byte array variable instead of yourByteArray
input = new ByteArrayInputStream(yourByteArray)
// use your object variable instead of yourObject
yourObject = null
input.withObjectInputStream(getClass().classLoader){ ois -> yourObject = ois.readObject() }
Use ObjectOutputStream to serialize updated objects and save them to an XML response:
output = new ByteArrayOutputStream()
output.withObjectOutputStream { oos -> oos << yourObject }
//save serialized data as byte array
output.toByteArray()