缘起
最近一段时间在开发 IDEA 插件, UI 界面需要使用到国际化配置, 于是就看了看 IDEA 是怎么实现的, 发现很简单, 正好能用到框架开发上.
打算为每个 atom-kernel 模块配置一个国际化配置, 同时将错误信息配置化. 因为是框架底层的组件, 如果使用 Spring Boot 的 i18n 实现就太重了, 因此需要一种超轻量级的实现方式.
IDEA 中如何实现 i18n
IDEA 使用 ResourceBundle 这个类实现了 i18n, 源码如下:
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public abstract class AbstractBundle {
private static final Logger LOG = Logger.getInstance("#com.intellij.AbstractBundle");
private Reference<ResourceBundle> myBundle;
@NonNls private final String myPathToBundle;
protected AbstractBundle(@NonNls @NotNull String pathToBundle) {
myPathToBundle = pathToBundle;
}
@NotNull
public String getMessage(@NotNull String key, @NotNull Object... params) {
return CommonBundle.message(getBundle(), key, params);
}
private ResourceBundle getBundle() {
ResourceBundle bundle = com.intellij.reference.SoftReference.dereference(myBundle);
if (bundle == null) {
bundle = getResourceBundle(myPathToBundle, getClass().getClassLoader());
myBundle = new SoftReference<>(bundle);
}
return bundle;
}
private static final Map<ClassLoader, Map<String, ResourceBundle>> ourCache =
ConcurrentFactoryMap.createWeakMap(k -> ContainerUtil.createConcurrentSoftValueMap());
public static ResourceBundle getResourceBundle(@NotNull String pathToBundle, @NotNull ClassLoader loader) {
Map<String, ResourceBundle> map = ourCache.get(loader);
ResourceBundle result = map.get(pathToBundle);
if (result == null) {
try {
ResourceBundle.Control control = ResourceBundle.Control.getControl(ResourceBundle.Control.FORMAT_PROPERTIES);
result = ResourceBundle.getBundle(pathToBundle, Locale.getDefault(), loader, control);
}
catch (MissingResourceException e) {
LOG.info("Cannot load resource bundle from *.properties file, falling back to slow class loading: " + pathToBundle);
ResourceBundle.clearCache(loader);
result = ResourceBundle.getBundle(pathToBundle, Locale.getDefault(), loader);
}
map.put(pathToBundle, result);
}
return result;
}
}
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实现自己的 Bundle 类:
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| public class IdeBundle extends AbstractBundle {
public static String message(@NotNull @PropertyKey(resourceBundle = BUNDLE) String key, @NotNull Object... params) {
return INSTANCE.getMessage(key, params);
}
public static final String BUNDLE = "messages.IdeBundle";
private static final IdeBundle INSTANCE = new IdeBundle();
private IdeBundle() {
super(BUNDLE);
}
}
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添加配置文件:
还需要在 classpath 中添加一个 messages 目录, 然后添加 IdeBundle.properties 配置文件, 或者可以直接使用 IDEA 新增资源包, 需要注意的是, messages.IdeBundle 表示在 messages 目录下的 IdeBundle.properties 文件, 一定不能错:
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| error.malformed.url=Malformed url: {0}
browsers.explorer=Internet Explorer
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使用方式:
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| # 有占位符的
IdeBundle.message("error.malformed.url", "xxx")
# 无占位符
IdeBundle.message("browsers.explorer")
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从上面可以看出, 直接 JDK 自带的 ResourceBundle 类实现了国际化和占位符替换的功能, 刚好符合我的要求, 因此打算使用这种方式来实现一下.
实现逻辑
我需要的功能:
- 国际化;
- 占位符替换;
IDEA 的 AbstractBundle 有很多我不需要的功能, 做了一些简单的修改后完全符合我的要求:
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| @Slf4j
public abstract class AbstractBundle {
private static final Map<ClassLoader, Map<String, ResourceBundle>> CACHE =
ConcurrentFactoryMap.createWeakMap(k -> new ConcurrentSoftValueHashMap<>());
@NonNls
private final String myPathToBundle;
private Reference<ResourceBundle> myBundle;
@Contract(pure = true)
protected AbstractBundle(@NonNls @NotNull String pathToBundle) {
this.myPathToBundle = pathToBundle;
}
@NotNull
public Supplier<String> getLazyMessage(@NotNull String key, Object... params) {
return () -> this.getMessage(key, params);
}
@NotNull
public String getMessage(@NotNull String key, Object... params) {
return message(this.getResourceBundle(), key, params);
}
@Nls
@NotNull
public static String message(@NotNull ResourceBundle bundle, @NotNull String key, Object... params) {
return messageOrDefault(bundle, key, null, params);
}
public ResourceBundle getResourceBundle() {
ResourceBundle bundle = SoftReference.dereference(this.myBundle);
if (bundle == null) {
bundle = this.getResourceBundle(this.myPathToBundle, this.getClass().getClassLoader());
this.myBundle = new SoftReference<>(bundle);
}
return bundle;
}
@NotNull
public ResourceBundle getResourceBundle(@NotNull String pathToBundle, @NotNull ClassLoader loader) {
Map<String, ResourceBundle> map = CACHE.get(loader);
ResourceBundle result = map.get(pathToBundle);
if (result == null) {
try {
ResourceBundle.Control control = ResourceBundle.Control.getControl(ResourceBundle.Control.FORMAT_PROPERTIES);
result = this.findBundle(pathToBundle, loader, control);
} catch (MissingResourceException e) {
log.info("无法从 *.properties 文件中加载资源包，降级为慢的类加载： " + pathToBundle);
ResourceBundle.clearCache(loader);
result = ResourceBundle.getBundle(pathToBundle, Locale.getDefault(), loader);
}
map.put(pathToBundle, result);
}
return result;
}
protected ResourceBundle findBundle(@NotNull String pathToBundle, @NotNull ClassLoader loader,
@NotNull ResourceBundle.Control control) {
return ResourceBundle.getBundle(pathToBundle, Locale.getDefault(), loader, control);
}
public static String messageOrDefault(@Nullable ResourceBundle bundle,
@NotNull String key,
@Nullable String defaultValue,
@NotNull Object... params) {
if (bundle != null) {
String value;
try {
value = bundle.getString(key);
} catch (MissingResourceException e) {
value = useDefaultValue(bundle, key, defaultValue);
}
return postprocessValue(bundle, value, params);
}
return defaultValue;
}
@NotNull
static String useDefaultValue(ResourceBundle bundle, @NotNull String key, @Nullable String defaultValue) {
if (defaultValue != null) {
return defaultValue;
}
log.error("在资源包中 {} 未找到键: [{}]", bundle.getBaseBundleName(), key);
return StringPool.NULL_STRING;
}
static String postprocessValue(@NotNull ResourceBundle bundle, @NotNull String value, @NotNull Object @NotNull [] params) {
if (params.length > 0 && value.indexOf('{') >= 0) {
if (value.contains("{0")) {
Locale locale = bundle.getLocale();
try {
MessageFormat format = locale != null ? new MessageFormat(value, locale) : new MessageFormat(value);
OrdinalFormat.apply(format);
value = format.format(params);
} catch (IllegalArgumentException e) {
value = "!format 错误: `" + value + "`!";
}
} else {
value = StrFormatter.format(value, params);
}
}
return value;
}
}
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创建绑定类:
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| public final class CoreBundle extends DynamicBundle {
@NonNls
private static final String BUNDLE = "i18n.CoreBundle";
private static final CoreBundle INSTANCE = new CoreBundle();
@Contract(pure = true)
private CoreBundle() {
super(BUNDLE);
}
@NotNull
public static String message(@NotNull String key, Object... params) {
return INSTANCE.getMessage(key, params);
}
public static @NotNull Supplier<String> messagePointer(@NotNull String key, Object... params) {
return INSTANCE.getLazyMessage(key, params);
}
}
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上面的代码基本上是固定的写法, 只需要修改 BUNDLE 即可, 然后创建国际化配置文件:
测试一下:
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| @Slf4j
class CoreBundleTest {
@Test
void test_1() {
log.info("{}", CoreBundle.message("code.param.verify.error"));
log.info("{}", CoreBundle.message("aaa"));
log.info("{}", CoreBundle.messagePointer("code.param.verify.error", "aaaaa").get());
}
}
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输出:
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| [main] INFO io.github.atom.kernel.core.CoreBundleTest - 参数校验失败: [{}]
[main] ERROR io.github.atom.kernel.core.bundle.AbstractBundle - 在资源包 [i18n.CoreBundle] 未找到键: [aaa]
[main] INFO io.github.atom.kernel.core.CoreBundleTest - N/A
[main] INFO io.github.atom.kernel.core.CoreBundleTest - 参数校验失败: [aaaaa]
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