10.15 Serializable Objects

In Java terminology, a serializable object typically refers to an object that implements the java.io.Serializable interface and therefore supports serialization to and from a byte stream. All Java classes generated from Slice definitions implement the java.io.Serializable interface.

In addition to serializing Slice types, applications may also need to incorporate foreign types into their Slice definitions. As discussed in Section 4.18, you can pass Java serializable objects directly as operation parameters or as fields of another data type. For example:

["java:serializable:SomePackage.JavaClass"]
sequence<byte> JavaObj;
struct MyStruct {
    int i;
    JavaObj o;
};

interface Example {
    void op(JavaObj inObj, MyStruct s, out JavaObj outObj);
};

The generated code for MyStruct contains a member i of type int and a member o of type SomePackage.JavaClass:

public final class MyStruct implements java.lang.Cloneable {
    public int i;
    public SomePackage.JavaClass o;

    // ...
}

Similarly, the signature for op has parameters of type JavaClass and MyStruct for the in-parameters, and Ice.Holder<SomePackage.JavaClass> for the out-parameter. (Out-parameters are always passed as Ice.Holder<class>.)

void op(SomePackage.JavaClass inObj,
        MyStruct s,
        Ice.Holder<SomePackage.JavaClass> outObj);

Of course, your client and server code must have an implementation of JavaClass that derives from java.io.Serializable:

package SomePackage;

public class JavaClass implements java.io.Serializable {
    // ...
}

You can implement this class in any way you see fit—the Ice run time does not place any other requirements on the implementation.