Java反射：我如何获得java类的所有getter方法并调用它们 [英] Java Reflection: How can i get the all getter methods of a java class and invoke them
问题描述
我写了一个有很多getter的java类..现在我想获取所有getter方法并在某个时候调用它们。我知道有一些方法，比如getMethods（）或getMethod（String name，Class ... parameterTypes） ，但我只是想得到吸气剂......，使用正则表达式？谁能告诉我？谢谢！
I write a java class which has many getters..now i want to get all getter methods and invoke them sometime..I know there are methods such as getMethods() or getMethod(String name, Class... parameterTypes) ,but i just want to get the getter indeed..., use regex? anyone can tell me ?Thanks!
推荐答案
不要使用正则表达式，请使用 Introspector ：
Don't use regex, use the Introspector:
for(PropertyDescriptor propertyDescriptor :
Introspector.getBeanInfo(yourClass).getPropertyDescriptors()){
// propertyEditor.getReadMethod() exposes the getter
// btw, this may be null if you have a write-only property
System.out.println(propertyDescriptor.getReadMethod());
}
通常你不需要来自Object.class的属性，所以你要使用带有两个参数的方法：
Usually you don't want properties from Object.class, so you'd use the method with two parameters:
Introspector.getBeanInfo(yourClass, stopClass)
// usually with Object.class as 2nd param
// the first class is inclusive, the second exclusive
BTW：那里是为您做这些的框架，并为您提供高级视图。例如。
commons / beanutils有方法
BTW: there are frameworks that do that for you and present you a high-level view. E.g. commons/beanutils has the method
Map<String, String> properties = BeanUtils.describe(yourObject);
（ docs here ）这样做：找到并执行所有getter并将结果存储在地图中。不幸的是， BeanUtils.describe（）在返回之前将所有属性值转换为字符串。 WTF。谢谢@danw
(docs here) which does just that: find and execute all the getters and store the result in a map. Unfortunately, BeanUtils.describe() converts all the property values to Strings before returning. WTF. Thanks @danw
更新：
这是一个Java 8方法，它根据对象的bean属性返回 Map< String，Object> 。
Here's a Java 8 method that returns a Map<String, Object> based on an object's bean properties.
public static Map<String, Object> beanProperties(Object bean) {
try {
return Arrays.asList(
Introspector.getBeanInfo(bean.getClass(), Object.class)
.getPropertyDescriptors()
)
.stream()
// filter out properties with setters only
.filter(pd -> Objects.nonNull(pd.getReadMethod()))
.collect(Collectors.toMap(
// bean property name
PropertyDescriptor::getName,
pd -> { // invoke method to get value
try {
return pd.getReadMethod().invoke(bean);
} catch (Exception e) {
// replace this with better error handling
return null;
}
}));
} catch (IntrospectionException e) {
// and this, too
return Collections.emptyMap();
}
}
您可能希望使错误处理更加健壮，尽管。对于样板，很抱歉，检查异常会阻止我们在这里完全正常运行。
You probably want to make error handling more robust, though. Sorry for the boilerplate, checked exceptions prevent us from going fully functional here.
原来Collectors.toMap（）讨厌空值。以下是上述代码的更为命令式版本：
Turns out that Collectors.toMap() hates null values. Here's a more imperative version of the above code:
public static Map<String, Object> beanProperties(Object bean) {
try {
Map<String, Object> map = new HashMap<>();
Arrays.asList(Introspector.getBeanInfo(bean.getClass(), Object.class)
.getPropertyDescriptors())
.stream()
// filter out properties with setters only
.filter(pd -> Objects.nonNull(pd.getReadMethod()))
.forEach(pd -> { // invoke method to get value
try {
Object value = pd.getReadMethod().invoke(bean);
if (value != null) {
map.put(pd.getName(), value);
}
} catch (Exception e) {
// add proper error handling here
}
});
return map;
} catch (IntrospectionException e) {
// and here, too
return Collections.emptyMap();
}
}
以下更简洁的方式使用相同的功能，使用 JavaSlang ：
Here's the same functionality in a more concise way, using JavaSlang:
public static Map<String, Object> javaSlangBeanProperties(Object bean) {
try {
return Stream.of(Introspector.getBeanInfo(bean.getClass(), Object.class)
.getPropertyDescriptors())
.filter(pd -> pd.getReadMethod() != null)
.toJavaMap(pd -> {
try {
return new Tuple2<>(
pd.getName(),
pd.getReadMethod().invoke(bean));
} catch (Exception e) {
throw new IllegalStateException();
}
});
} catch (IntrospectionException e) {
throw new IllegalStateException();
}
}
这是一个番石榴版本：
public static Map<String, Object> guavaBeanProperties(Object bean) {
Object NULL = new Object();
try {
return Maps.transformValues(
Arrays.stream(
Introspector.getBeanInfo(bean.getClass(), Object.class)
.getPropertyDescriptors())
.filter(pd -> Objects.nonNull(pd.getReadMethod()))
.collect(ImmutableMap::<String, Object>builder,
(builder, pd) -> {
try {
Object result = pd.getReadMethod()
.invoke(bean);
builder.put(pd.getName(),
firstNonNull(result, NULL));
} catch (Exception e) {
throw propagate(e);
}
},
(left, right) -> left.putAll(right.build()))
.build(), v -> v == NULL ? null : v);
} catch (IntrospectionException e) {
throw propagate(e);
}
}
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