在struts2中可以在struts.properties文件中设置default local。如:struts.locale=zh_CN
查看源代码发现他是通过annotation Inject来设置的。
@Inject(value=StrutsConstants.STRUTS_LOCALE, required=false)
public static void setDefaultLocale(String val) {
defaultLocale = val;
}
public static final String STRUTS_LOCALE = "struts.locale";
接下来我们看一下它是怎么通过annotation来设置的呢。先调用addInjectorsForMembers()方法拿到有inject标签的方法,然后调用 injector.inject(context, null);方法。
void injectStatics(List<Class<?>> staticInjections) {
final List<Injector> injectors = new ArrayList<Injector>();
for (Class<?> clazz : staticInjections) {
addInjectorsForFields(clazz.getDeclaredFields(), true, injectors);
addInjectorsForMethods(clazz.getDeclaredMethods(), true, injectors);
}
callInContext(new ContextualCallable<Void>() {
public Void call(InternalContext context) {
for (Injector injector : injectors) {
injector.inject(context, null);
}
return null;
}
});
}
void addInjectorsForFields(Field[] fields, boolean statics,
List<Injector> injectors) {
addInjectorsForMembers(Arrays.asList(fields), statics, injectors,
new InjectorFactory<Field>() {
public Injector create(ContainerImpl container, Field field,
String name) throws MissingDependencyException {
return new FieldInjector(container, field, name);
}
});
}
//通过member.getAnnotation(Inject.class);方法拿到那些有Inject标签的方法,然后保存在
injectors里面。
<M extends Member & AnnotatedElement> void addInjectorsForMembers(
List<M> members, boolean statics, List<Injector> injectors,
InjectorFactory<M> injectorFactory) {
for (M member : members) {
if (isStatic(member) == statics) {
Inject inject = member.getAnnotation(Inject.class);
if (inject != null) {
try {
injectors.add(injectorFactory.create(this, member, inject.value()));
} catch (MissingDependencyException e) {
if (inject.required()) {
throw new DependencyException(e);
}
}
}
}
}
}
然后在inject方法里面调用 method.invoke()方法,此处method是定义了inject的标签,此处是setDefaultLocale方法getParameters(method, context, parameterInjectors)返回参数,此处为‘zh_CN’。这样就通过反射设置进去了。
public void inject(InternalContext context, Object o) {
try {
method.invoke(o, getParameters(method, context, parameterInjectors));
} catch (Exception e) {
throw new RuntimeException(e);
}
}
}
总结:此处涉及了两个方面,一是annotation的使用,二是反射的使用。这两个知识点都很常用。比如我上次做的为了减少struts的配置,用annotation标识那些类是Action类。struts.locale=zh_CN 中的配置应该和用户浏览器的配置一样,不然就会发生将string转成时间格式不匹配的错误