Java对象到JSON的转换

Question

I have a Java object as below

    public class Command {
    private String cmd;
    private Object data;
}

I want JSON Conversion of this Object to look as below

{"cmd":"getorder","data":{"when":"today"}}

How do I do this without changing the Class definition?

I know how to use GSON or Jackson library. I am having trouble assigning values to or initializing (Object) data above, so that it properly converts to {"when":"today"} when I use those libraries.

Thanks

Answer 1

您可以尝试使用Gson库，它非常易于使用，并且还可以执行反向操作

Answer 2

Depending on your needs you might consider to add a handwritten json formatter for your class (of yourse this interferes with your demand to not change the class definition) but in fact it gives you max flexibility without 3rd party dependencies. If you strictly let all your Objects overwrite toString() to give json formatted string representation you could eg

String toString() {
    StringBuffer result = new StringBuffer();
    result.add("{ \"cmd\":" + this.cmd);
    result.add(",");
    result.add( \"data\":" + data.toString());
    result.add("}");
    return result.toString();
}

In case your need to not change the class definition appears more important than the mentioned advanteges there is aa nice json library avaialble on code.google.com named "simple json" ( https://code.google.com/p/json-simple/ ).