java 通过方法“迭代”
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原文地址: http://stackoverflow.com/questions/3316582/
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"Iterating" through methods
提问by
Let's say I've got a Java object that's got among others the following methods:
假设我有一个 Java 对象，其中包含以下方法：
public String getField1();
public String getField2();
public String getField3();
public String getField4();
public String getField5();
Is there a way to iterate through these methods and call 'em like the following code?
有没有办法遍历这些方法并像下面的代码一样调用它们？
String fields = "";
for(int i = 1; i <= 5; i ++){
fields += object.(getField+i) + " | ";
}
Thank you for your upcoming ideas.
感谢您即将提出的想法。
采纳答案by Sanjay Manohar
There is a way using reflection:
有一种使用反射的方法：
try{
Method m= object.getClass().getMethod("getField"+String.valueOf(i), new Class[]{});
fields+=(String)m.invoke(object);
}catch(...){...}
However:This business all smells of bad coding practice!
Can't you rewrite all the getFieldN()methods like this?
然而：这项业务充满了糟糕的编码实践！你不能getFieldN()像这样重写所有的方法吗？
String getField(int fieldNum)
You are asking for trouble by creating numbered methods. Remember that reflection is slow and should only be used when String-based method calls are absolutely essential to the flow of your program. I sometimes use this technique for user-defined scripting languages where you have to get a method by name. That isn't the case at all here, your calls are integer-indexed. You should therefore keep the integer as a parameter.
您通过创建编号方法来自找麻烦。请记住，反射很慢，并且只应在基于字符串的方法调用对程序流程绝对必要时使用。我有时将这种技术用于用户定义的脚本语言，您必须按名称获取方法。这里根本不是这种情况，您的电话是integer-indexed。因此，您应该保留整数作为参数。
If this is legacy code and you are absolutely unable to change this bad coding, then you might be better off creating a new method getMethod(int)as above to wrap the existing methods, that just delegates to the numbered getMethodN()methods.
如果这是遗留代码并且您绝对无法更改这种糟糕的编码，那么您最好创建一个getMethod(int)如上所述的新方法来包装现有方法，该方法仅委托给编号的getMethodN()方法。
回答by Alberto Zaccagni
Class yourClass = YourClass.class;
for (Method method : yourClass.getMethods()){
method.invoke(obj, args);
}
See this guidefor reference.
请参阅本指南以供参考。
回答by stacker
To be able to select specific fields and order you should specifiy them i.e. by a list of field names.
为了能够选择特定的字段和顺序，您应该通过字段名称列表来指定它们。
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Date;
import java.util.StringTokenizer;
public class CsvReflect {
int a = 10;
String b = "test";
Date d = new Date();
public int getA() {
return a;
}
public String getB() {
return b;
}
public Date getD() {
return d;
}
public static String toCsv(Object obj, String fields, String separator) throws SecurityException, NoSuchMethodException, IllegalArgumentException, IllegalAccessException, InvocationTargetException {
StringBuilder sb = new StringBuilder();
StringTokenizer st = new StringTokenizer(fields,",");
while ( st.hasMoreElements() ) {
String field = st.nextToken();
Method getter = obj.getClass().getMethod("get"+ field, new Class[]{});
String val = "" + getter.invoke(obj, new Class[]{});
sb.append( val );
if ( st.hasMoreElements() ) {
sb.append(separator);
}
}
return sb.toString();
}
public static void main(String[] args) throws SecurityException, IllegalArgumentException, NoSuchMethodException, IllegalAccessException, InvocationTargetException {
CsvReflect csv = new CsvReflect();
System.out.println( csv.toCsv( csv ,"A,B,D", "|" ));
}
}
