从泽西休息返回复杂的对象

Question

我正在开发使用Jersey Rest for Services的项目。我有一个Project类，它有ArrayList of Activities。

    package com.test.services.model;

import java.util.ArrayList;

import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement
public class Project {


    public Project(){

        ArrayList<Activity> activities = new ArrayList<Activity>();

        Activity activity = new Activity();
        activity.setId("act1");
        activity.setName("Activity 1");

        activities.add(activity);

        activity = new Activity();
        activity.setId("act2");
        activity.setName("Activity 2");

        activities.add(activity);

        this.setActivities(activities);

    }


    private ArrayList<Activity> activities;

    private String name;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getId() {
        return this.id;
    }

    public void setId(int id) {
        this.id = id;
    }

    @XmlElement(name="activities")
    public ArrayList<Activity> getActivities() {
        return activities;
    }

    public void setActivities(ArrayList<Activity> activities) {
        this.activities = activities;
    }

    @XmlElement(name="Codes")
    public ArrayList<String> getCodes() {

        ArrayList<String> str = new ArrayList<String>();

        str.add("Hello");
        str.add("World");

        return str;
    }


    private int id;
}

这就是我的XML的样子

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<projects>
    <project>
        <activities/> // Empty
        <activities/> //Empty
        <Codes>Hello</Codes>
        <Codes>World</Codes>
        <id>1</id>
        <name>Project 1</name>
    </project>
    <project>
        <activities/>
        <activities/>
        <Codes>Hello</Codes>
        <Codes>World</Codes>
        <id>2</id>
        <name>Project 2</name>
    </project>
    <project>
        <activities/>
        <activities/>
        <Codes>Hello</Codes>
        <Codes>World</Codes>
        <id>3</id>
        <name>Project 3</name>
    </project>
    <project>
        <activities/>
        <activities/>
        <Codes>Hello</Codes>
        <Codes>World</Codes>
        <id>4</id>
        <name>Project 4</name>
    </project>
</projects>

我添加了空的ArrayList代码;查看ArrayList是否有任何问题。我不确定为什么在我的XML中返回空活动。

任何帮助将不胜感激

谢谢， [R