我正在尝试使用反射来调用带有varargs参数的方法。
并捕获了CCD_ 1。我搞不清楚这里出了什么问题。
代码:
public class ReflectionTest {
public ReflectionTest() { }
private void varargMethod(String string, Integer ... var) {
System.out.println("vargarMethod() called");
System.out.println(string + " Number of args: " + var.length
+ "nContents");
for (int i = 0; i < var.length; i++) {
System.out.printf(" args %d: %d", i, var[i]);
//System.out.println(" args " + i + ": " + var[i]);
}
System.out.println();
}
public static void main(String[] args) throws Exception {
Class[] parameterTypes = new Class[] { String.class, int.class, int.class, int.class };
//System.out.println(Arrays.toString(parameterTypes));
Method varMeth = test.getClass().getDeclaredMethod("varargMethod", parameterTypes);
System.out.println("varMeth" + varMeth);
Object[] arguments = new Object[] { new String("my perfect string"),
new Integer(10), new Integer(100), new Integer(47) };
varMeth.invoke(test, arguments);
它准确地抛出:
java.lang.NoSuchMethodException:反射测试.vargMethod(java.lang.String,int,int)
- 如何解决这个问题
varargs的参数类型应为Integer[].class
,因为varargs表达式指定该参数为变量数组参数。因此,正确的方法是:
Class[] parameterTypes = new Class[] { String.class, Integer[].class };
//System.out.println(Arrays.toString(parameterTypes));
ReflectionTest test = new ReflectionTest();
Method varMeth = test.getClass().getDeclaredMethod("varargMethod",
parameterTypes);
System.out.println("varMeth" + varMeth);
Object[] arguments = new Object[] { new String("my perfect string"),
new Integer[]{10, 100, 47}
};
varMeth.invoke(test, arguments);
如果编译.java文件,然后反编译.class文件中,您将看到该方法的声明:
private transient void varargMethod(String string, Integer var[])
所以这里是你的代码修复。
import java.lang.reflect.Method;
public class ReflectionTest {
public ReflectionTest() { }
private void varargMethod(String string, Integer ... var) {
System.out.println("vargarMethod() called");
System.out.println(string + " Number of args: " + var.length
+ "nContents");
for (int i = 0; i < var.length; i++) {
System.out.printf(" args %d: %d", i, var[i]);
//System.out.println(" args " + i + ": " + var[i]);
}
System.out.println();
}
public static void main(String[] args) throws Exception {
ReflectionTest test = new ReflectionTest();
Class[] parameterTypes = new Class[] { String.class, Integer[].class };
//System.out.println(Arrays.toString(parameterTypes));
Method varMeth = test.getClass().getDeclaredMethod("varargMethod", parameterTypes);
System.out.println("varMeth" + varMeth);
Object[] arguments = new Object[] { new String("my perfect string"),
new Integer[] { new Integer(10), new Integer(100), new Integer(47) } };
varMeth.invoke(test, arguments);
}
}
这是固定的代码,改动很小。更改内联评论:
import java.lang.reflect.Method;
public class ReflectionTest {
public ReflectionTest() {}
private void varargMethod(String string, Integer... var) {
System.out.println("vargarMethod() called");
System.out.println(string + " Number of args: " + var.length + "nContents:");
for (int i = 0; i < var.length; i++) {
System.out.printf(" args %d: %d", i, var[i]);
}
System.out.println();
}
public static void main(String[] args) throws Exception {
Class[] parameterTypes = new Class[] {
String.class,
Integer[].class // use array to represent varargs
};
//System.out.println(Arrays.toString(parameterTypes));
ReflectionTest test = new ReflectionTest();
Method varMeth = test.getClass().getDeclaredMethod("varargMethod", parameterTypes);
System.out.println("varMeth" + varMeth);
Object[] arguments = new Object[]{
"my perfect string",
new Integer[]{10, 100, 47} // again use array for varargs
};
varMeth.invoke(test, arguments);
}
}