java - 序列化 java.lang.Locale

Question

得到一个类，它可以使用 XMLEncoder 很好地序列化为 xml，其中包含所有变量。除了保存 java.util.Locale 的那个。可能有什么技巧？

Answer 1

问题是 java.util.Locale 不是 bean 。来自 XMLEncoder文档:

The XMLEncoder class is a complementary alternative to the ObjectOutputStream and can used to generate a textual representation of a JavaBean in the same way that the ObjectOutputStream can be used to create binary representation of Serializable objects.

但是，API 允许您使用 PersistenceDelegates 来序列化非 bean 类型:

示例 bean:

public class MyBean implements Serializable {

    private static final long serialVersionUID = 1L;

    private Locale locale;
    private String foo;

    public MyBean() {
    }

    public Locale getLocale() {
        return locale;
    }

    public void setLocale(Locale locale) {
        this.locale = locale;
    }

    public String getFoo() {
        return foo;
    }

    public void setFoo(String foo) {
        this.foo = foo;
    }

}

序列化包含区域设置类型的数据图:

public class MyBeanTest {

    public static void main(String[] args) throws Exception {
        // quick and dirty test

        MyBean c = new MyBean();
        c.setLocale(Locale.CHINA);
        c.setFoo("foo");

        ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
        XMLEncoder encoder = new XMLEncoder(outputStream);
        encoder.setPersistenceDelegate(Locale.class, new PersistenceDelegate() {
            protected Expression instantiate(Object oldInstance, Encoder out) {
                Locale l = (Locale) oldInstance;
                return new Expression(oldInstance, oldInstance.getClass(),
                        "new", new Object[] { l.getLanguage(), l.getCountry(),
                                l.getVariant() });
            }
        });
        encoder.writeObject(c);
        encoder.flush();
        encoder.close();

        System.out.println(outputStream.toString("UTF-8"));

        ByteArrayInputStream bain = new ByteArrayInputStream(outputStream
                .toByteArray());
        XMLDecoder decoder = new XMLDecoder(bain);

        c = (MyBean) decoder.readObject();

        System.out.println("===================");
        System.out.println(c.getLocale());
        System.out.println(c.getFoo());
    }

}

这是描述如何在反序列化时实例化对象的代码部分 - 它将构造函数参数设置为三个字符串值:

    new PersistenceDelegate() {
        protected Expression instantiate(Object oldInstance, Encoder out) {
            Locale l = (Locale) oldInstance;
            return new Expression(oldInstance, oldInstance.getClass(),
                    "new", new Object[] { l.getLanguage(), l.getCountry(),
                            l.getVariant() });
        }
    }

阅读Using XMLEncoder作者:Philip Milne，了解更多信息。

除此之外，以文本形式存储区域设置信息并在需要时使用它来查找适当的 Locale 对象可能会更明智。这样，您在序列化对象时不需要特殊情况代码并使其更加可移植。