Make JsonNode Serializable

问题

This seems to be simple but I failed to get a serialized JsonNode deserialized. Here is my test class

import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;

public class Foo implements Serializable {
    private String string;
    private transient JsonNode jsonNode;

    public Foo(String string, JsonNode jsonNode) {
        this.string = string;
        this.jsonNode = jsonNode;
    }

    private void writeObject(ObjectOutputStream out) throws IOException {
        out.defaultWriteObject();
        if (this.jsonNode != null) out.writeObject((new ObjectMapper()).writeValueAsBytes(this.jsonNode));
//        out.writeObject(this.jsonNode.textValue());
    }

    private void readObject(ObjectInputStream in) throws IOException,ClassNotFoundException {
        in.defaultReadObject();
        this.jsonNode = (new ObjectMapper()).readValue(in, JsonNode.class);
    }
}

When I tried to deserialize I got this error

com.fasterxml.jackson.databind.JsonMappingException: No content to map due to end-of-input

Here is the unit test

import com.fasterxml.jackson.databind.node.JsonNodeFactory;
import com.fasterxml.jackson.databind.node.ObjectNode;
import org.testng.annotations.Test;

import java.io.*;

import static org.testng.Assert.assertEquals;

public class FooTest {
    @Test
    public void testSerialization() {
        JsonNodeFactory nodeFactory = new JsonNodeFactory(false);
        ObjectNode node = nodeFactory.objectNode();
        ObjectNode child = nodeFactory.objectNode(); // the child
        child.put("message", "test");
        node.put("notification", child);

        Foo foo = new Foo("Bar", node);

        String fileName = "foo.ser";
        try (
                OutputStream file = new FileOutputStream(fileName);
                OutputStream buffer = new BufferedOutputStream(file);
                ObjectOutput output = new ObjectOutputStream(buffer);
        ){
            output.writeObject(foo);
        }
        catch(IOException ex){
            ex.getStackTrace();
        }

        Foo fooNew = null;

        //deserialize the ser file
        try(
                InputStream file = new FileInputStream(fileName);
                InputStream buffer = new BufferedInputStream(file);
                ObjectInput input = new ObjectInputStream (buffer);
        ){
            //deserialize the Object
            fooNew = (Foo) input.readObject();
        }
        catch(ClassNotFoundException ex){
            ex.printStackTrace();
        }
        catch(IOException ex){
            ex.printStackTrace();
        }

        assertEquals(foo, fooNew);
    }
}

回答1:

Your read and write operations are not matched.

On the write side you use ObjectOutputStream.writeObject(Object) to write a byte[] containing the serialized JSON content. On the read side you try to read raw bytes off the stream with ObjectMapper.readValue(InputStream, Class) when you actually need to read a byte[] object first as that is what you wrote and then use ObjectMapper.readValue(byte[], Class).

Alternatively and probably a better solution is you could use ObjectMapper.writeValue(OutputStream, Object) instead on the write side.

Try this:

private void writeObject(ObjectOutputStream out) throws IOException {
    out.defaultWriteObject();
    if(jsonNode == null){
        out.writeBoolean(false);
    } else {
        out.writeBoolean(true);
        new ObjectMapper().configure(JsonGenerator.Feature.AUTO_CLOSE_TARGET, false).writeValue(out, jsonNode);
    }
}

private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
    in.defaultReadObject();
    if(in.readBoolean()){
        this.jsonNode = new ObjectMapper().configure(JsonParser.Feature.AUTO_CLOSE_SOURCE, false).readValue(in, JsonNode.class);
    }     
}

来源：https://stackoverflow.com/questions/31861354/make-jsonnode-serializable

标签

java

json

serialization

jackson