java基础---->java中国际化的实现

　　应用程序的功能和代码设计考虑在不同地区运行的需要，其代码简化了不同本地版本的生产。开发这样的程序的过程，就称为国际化。今天，我们就开始学习java中国际化的代码实现。

Java国际化主要通过如下3个类完成

• java.util.ResourceBundle:用于加载一个资源包
• java.util.Locale：对应一个特定的国家/区域、语言环境。
• java.text.MessageFormat：用于将消息格式化

为实现程序的国际化，必须提供程序所需要的资源文件。资源文件的内容由key-value对组成。资源文件的命名可以有3种格式：

• basename_language_country.properties
• basename_language.properties
• basename_properties

java se中国际化的实现

java se的国际化实现，项目结构如下：

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" 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首先定义属性文件，它的命名规则见上述。具体代码ResourceBundleTest.java如下

一、得到所有可用的Locale，结果太长就不列出了，一共156列

public static void getLocales() {
    Locale[] availableLocales = Locale.getAvailableLocales();
    System.out.println(availableLocales.length);
    for (Locale locale : availableLocales) {
        System.out.println(locale.toString());
    }
}

二、 使用系统默认的Locale

public static void useDefaultLocale() {
    ResourceBundle resourceBundle = ResourceBundle.getBundle("locale.myres");
    String string = resourceBundle.getString("name");
    System.out.println(string);
}

ResourceBundle.getBundle("locale.myres")与ResourceBundle.getBundle("locale.myres", Locale.getDefault())一样。

三、 使用自己指定的Locale

public static void useOwnLocale() {
    Locale locale = new Locale("zh", "CN");
    ResourceBundle resourceBundle = ResourceBundle.getBundle("locale.myres", locale);
    String string = resourceBundle.getString("name");
    System.out.println(string);
}

四、 使用带占位符的消息

public static void getMessage() {
    ResourceBundle resourceBundle = ResourceBundle.getBundle("locale/myres");
    String message = resourceBundle.getString("message");
    System.out.println(MessageFormat.format(message, "huhx", "刘力"));
}

myres_zh_CN.properties文件中有：

message=My name is {0}—, and I love you. --{1}

打印结果： My name is huhx—, and I love you. --刘力

五、 使用类文件代替资源文件

Java允许使用类文件来代替资源文件，即手动书写代码来实现国际化，

• 该类要求继承于ListResourceBundle,并重写getContents方法该方法返回Object数组，该数组的每一个项都是key-value对。
• 类的名字必须为basename_language_contry，这与属性文件的命名相似

在locale包下增加myres_zh_CN.java类，内容如下：

package locale;

import java.util.ListResourceBundle;

public class myres_zh_CN extends ListResourceBundle {
    private final Object myData[][] = { { "message", "Hello， {0} and {1}" }, { "test", "test" } };

    @Override
    protected Object[][] getContents() {
        return myData;
    }
}

在Main中的测试使用代码：

public static void getMessage() {
    ResourceBundle resourceBundle = ResourceBundle.getBundle("locale.myres");
    String message = resourceBundle.getString("message");
    System.out.println(MessageFormat.format(message, "huhx", "刘力"));
}

打印结果：Hello， huhx and 刘力

注意：如果系统同时存在资源文件、类文件，系统将以类文件为主，而不会调用资源文件。例如对于basename为myres的这一系列中文资源文件，系统搜索顺序如下

1. myres_zh_CN.java
2. myres_zh_CN.properties
3. myres_zh.java
4. myres_zh.properties
5. myres.java
6. myres.properties

如果getBundle的参数是“locale/myres”，那么位于locale的对应类就不会去查找，只会去查找属性文件。只有“locale.myres”才会先查找类，再查找属性文件

六、我们看一下ResourceBundle的getString(key)方法的源码，实际上是调用getObject(key)方法

public final Object getObject(String key) {
    Object obj = handleGetObject(key);
    if (obj == null) {
        if (parent != null) {
            obj = parent.getObject(key);
        }
        if (obj == null)
            throw new MissingResourceException("Can't find resource for bundle "
                                               +this.getClass().getName()
                                               +", key "+key,
                                               this.getClass().getName(),
                                               key);
    }
    return obj;
}

首先会调用handleGetObject方法，代码如下：

public final Object handleGetObject(String key) {
    // lazily load the lookup hashtable.
    if (lookup == null) {
        loadLookup();
    }
    if (key == null) {
        throw new NullPointerException();
    }
    return lookup.get(key); // this class ignores locales
}

lookup是Map<String,Object>，声明为空。执行loadLookup()方法

private synchronized void loadLookup() {
    if (lookup != null)
        return;

    Object[][] contents = getContents();
    HashMap<String,Object> temp = new HashMap<>(contents.length);
    for (int i = 0; i < contents.length; ++i) {
        // key must be non-null String, value must be non-null
        String key = (String) contents[i][0];
        Object value = contents[i][1];
        if (key == null || value == null) {
            throw new NullPointerException();
        }
        temp.put(key, value);
    }
    lookup = temp;
}

执行ListResourceBundle的getContens()方法，将返回的结果有规律的对应键值对存放在map中。

If ListResourceBundle or PropertyResourceBundle do not suit your needs, you can write your own ResourceBundle subclass. Your subclasses must override two methods: handleGetObject and getKeys(). 

友情链接