blocks|key|975856|text|Java有反射(java.reflection.*)，但是我建议你去看看像Apache+Beanutils这样的库，它会使这个过程比直接使用反射要简单得多。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|975857|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

Java has Reflection (java.reflection.*), but I would suggest looking into a library like Apache Beanutils, it will make the process much less hairy than using reflection directly.

blocks|key|975952|text|在java中，直接访问字段并不是很好的风格。我建议为bean的字段创建getter和setter方法，然后使用java.beans包中的Introspector和BeanInfo类。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|975953|MyBean+bean+=+new+MyBean();
BeanInfo+beanInfo+=+Introspector.getBeanInfo(MyBean.class);
for+(PropertyDescriptor+propertyDesc+:+beanInfo.getPropertyDescriptors())+{
++++String+propertyName+=+propertyDesc.getName();
++++Object+value+=+propertyDesc.getReadMethod().invoke(bean);
}|code-block|syntax|javascript|975954|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Accessing the fields directly is not really good style in java. I would suggest creating getter and setter methods for the fields of your bean and then using then Introspector and BeanInfo classes from the java.beans package.

<pre><code>MyBean bean = new MyBean();
BeanInfo beanInfo = Introspector.getBeanInfo(MyBean.class);
for (PropertyDescriptor propertyDesc : beanInfo.getPropertyDescriptors()) {
 String propertyName = propertyDesc.getName();
 Object value = propertyDesc.getReadMethod().invoke(bean);
}
</code></pre>

blocks|key|1190261|text|如果您的类符合JavaBeabs规范，我会同意Jörn's+answer，但如果您使用的是Spring，而类不符合规范，那么这是一个很好的选择。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1190262|Spring有一个名为ReflectionUtils的类，它提供了一些非常强大的功能，包括doWithFields(class,+callback)，这是一种访问者风格的方法，允许您使用如下回调对象迭代类字段：|1190263|public+void+analyze(Object+obj){
++++ReflectionUtils.doWithFields(obj.getClass(),+field+->+{

++++++++System.out.println("Field+name:+"+%2B+field.getName());
++++++++field.setAccessible(true);
++++++++System.out.println("Field+value:+"%2B+field.get(obj));

++++});
}|code-block|syntax|javascript|1190264|但是这里有一个警告:这个类被标记为“仅供内部使用”，如果你问我，这是一个遗憾|1190265|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/3333974/how-to-loop-over-a-class-attributes-in-java/3334217#3334217|1|http://static.springsource.org/spring/docs/3.0.3.RELEASE/javadoc-api/org/springframework/util/ReflectionUtils.html|2|http://static.springsource.org/spring/docs/3.0.3.RELEASE/javadoc-api/org/springframework/util/ReflectionUtils.html#doWithFields%2528java.lang.Class,%2520org.springframework.util.ReflectionUtils.FieldCallback%2529^0|N|D|0|0|B|F|1|19|T|2|0|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@]|9|@$A|Z|B|10|1|11]]|C|$]]|$1|D|3|E|5|6|7|12|8|@]|9|@$A|13|B|14|1|15]|$A|16|B|17|1|18]]|C|$]]|$1|F|3|G|5|H|7|19|8|@]|9|@]|C|$I|J]]|$1|K|3|L|5|6|7|1A|8|@]|9|@]|C|$]]|$1|M|3|-4|5|6|7|1B|8|@]|9|@]|C|$]]]|N|$O|$5|P|Q|R|C|$S|T]]|U|$5|P|Q|R|C|$S|V]]|W|$5|P|Q|R|C|$S|X]]]]

While I agree with <a href="https://stackoverflow.com/questions/3333974/how-to-loop-over-a-class-attributes-in-java/3334217#3334217">Jörn's answer</a> if your class conforms to the JavaBeabs spec, here is a good alternative if it doesn't and you use Spring.

Spring has a class named <a href="http://static.springsource.org/spring/docs/3.0.3.RELEASE/javadoc-api/org/springframework/util/ReflectionUtils.html" rel="noreferrer">ReflectionUtils</a> that offers some very powerful functionality, including <a href="http://static.springsource.org/spring/docs/3.0.3.RELEASE/javadoc-api/org/springframework/util/ReflectionUtils.html#doWithFields%28java.lang.Class,%20org.springframework.util.ReflectionUtils.FieldCallback%29" rel="noreferrer">doWithFields(class, callback)</a>, a visitor-style method that lets you iterate over a classes fields using a callback object like this:

<pre><code>public void analyze(Object obj){
 ReflectionUtils.doWithFields(obj.getClass(), field -&gt; {

 System.out.println("Field name: " + field.getName());
 field.setAccessible(true);
 System.out.println("Field value: "+ field.get(obj));

 });
}
</code></pre>

But here's a warning: the class is labeled as "for internal use only", which is a pity if you ask me

blocks|key|976095|text|迭代类字段并从object获取值的简单方法：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|976096|+Class<?>+c+=+obj.getClass();
+Field[]+fields+=+c.getDeclaredFields();
+Map<String,+Object>+temp+=+new+HashMap<String,+Object>();

+for(+Field+field+:+fields+){
++++++try+{
+++++++++++temp.put(field.getName().toString(),+field.get(obj));
++++++}+catch+(IllegalArgumentException+e1)+{
++++++}+catch+(IllegalAccessException+e1)+{
++++++}
+}|code-block|syntax|javascript|976097|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Simple way to iterate over class fields and obtain values from object:

<pre><code> Class&lt;?&gt; c = obj.getClass();
 Field[] fields = c.getDeclaredFields();
 Map&lt;String, Object&gt; temp = new HashMap&lt;String, Object&gt;();

 for( Field field : fields ){
 try {
 temp.put(field.getName().toString(), field.get(obj));
 } catch (IllegalArgumentException e1) {
 } catch (IllegalAccessException e1) {
 }
 }
</code></pre>

blocks|key|976149|text|以下是一个解决方案，它按字母顺序对属性进行排序，并将它们与它们的值一起打印出来：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|976150|public+void+logProperties()+throws+IllegalArgumentException,+IllegalAccessException+{
++Class<?>+aClass+=+this.getClass();
++Field[]+declaredFields+=+aClass.getDeclaredFields();
++Map<String,+String>+logEntries+=+new+HashMap<>();

++for+(Field+field+:+declaredFields)+{
++++field.setAccessible(true);

++++Object[]+arguments+=+new+Object[]{
++++++field.getName(),
++++++field.getType().getSimpleName(),
++++++String.valueOf(field.get(this))
++++};

++++String+template+=+"-+Property:+{0}+(Type:+{1},+Value:+{2})";
++++String+logMessage+=+System.getProperty("line.separator")
++++++++++++%2B+MessageFormat.format(template,+arguments);

++++logEntries.put(field.getName(),+logMessage);
++}

++SortedSet<String>+sortedLog+=+new+TreeSet<>(logEntries.keySet());

++StringBuilder+sb+=+new+StringBuilder("Class+properties:");

++Iterator<String>+it+=+sortedLog.iterator();
++while+(it.hasNext())+{
++++String+key+=+it.next();
++++sb.append(logEntries.get(key));
++}

++System.out.println(sb.toString());
}|code-block|syntax|javascript|976151|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Here is a solution which sorts the properties alphabetically and prints them all together with their values:

<pre><code>public void logProperties() throws IllegalArgumentException, IllegalAccessException {
 Class&lt;?&gt; aClass = this.getClass();
 Field[] declaredFields = aClass.getDeclaredFields();
 Map&lt;String, String&gt; logEntries = new HashMap&lt;&gt;();

 for (Field field : declaredFields) {
 field.setAccessible(true);

 Object[] arguments = new Object[]{
 field.getName(),
 field.getType().getSimpleName(),
 String.valueOf(field.get(this))
 };

 String template = "- Property: {0} (Type: {1}, Value: {2})";
 String logMessage = System.getProperty("line.separator")
 + MessageFormat.format(template, arguments);

 logEntries.put(field.getName(), logMessage);
 }

 SortedSet&lt;String&gt; sortedLog = new TreeSet&lt;&gt;(logEntries.keySet());

 StringBuilder sb = new StringBuilder("Class properties:");

 Iterator&lt;String&gt; it = sortedLog.iterator();
 while (it.hasNext()) {
 String key = it.next();
 sb.append(logEntries.get(key));
 }

 System.out.println(sb.toString());
}
</code></pre>

How can I loop over a class attributes in java dynamically.

For eg :

<pre><code>public class MyClass{
 private type1 att1;
 private type2 att2;
 ...

 public void function(){
 for(var in MyClass.Attributes){
 System.out.println(var.class);
 }
 }
}
</code></pre>

is this possible in Java?

How to loop over a Class attributes in Java?

Java

如何在java中动态循环一个类的属性。例如：public class MyClass{    private type1 att1;    private type2 att2;    ...    public void function(){        for(var in MyClass.Attributes...

问如何在Java中循环Class属性？
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