Java反射 - Java构造函数反射
以下四种方法来自 Class 类获取有关构造函数的信息:
Constructor[] getConstructors() Constructor[] getDeclaredConstructors() Constructor<T> getConstructor(Class... parameterTypes) Constructor<T> getDeclaredConstructor(Class... parameterTypes)
getConstructors()方法返回当前和超类的所有公共构造函数。
getDeclaredConstructors()方法返回当前类的所有声明的构造函数。
getConstructor（Class ... parameterTypes）和getDeclaredConstructor（Class ... parameterTypes）通过参数类型获取构造函数对象。
例子
以下代码显示了如何对构造函数执行反射。
import java.lang.reflect.Constructor;
import java.lang.reflect.Executable;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.lang.reflect.Parameter;
import java.util.ArrayList;class MyClass<T> {public MyClass(int i, int j, String s) {}public MyClass(T t) {}public int getInt(String a) {return 0;}
}public class Main {public static void main(String[] args) {Class<MyClass> c = MyClass.class;System.out.println("Constructors for " + c.getName());Constructor[] constructors = c.getConstructors();ArrayList<String> constructDescList = getConstructorsDesciption(constructors);for (String desc : constructDescList) {System.out.println(desc);}}public static ArrayList<String> getConstructorsDesciption(Constructor[] constructors) {ArrayList<String> constructorList = new ArrayList<>();for (Constructor constructor : constructors) {String modifiers = getModifiers(constructor);String constructorName = constructor.getName();constructorList.add(modifiers + " " + constructorName + "("+ getParameters(constructor) + ") " + getExceptionList(constructor));}return constructorList;}public static ArrayList<String> getParameters(Executable exec) {Parameter[] parms = exec.getParameters();ArrayList<String> parmList = new ArrayList<>();for (int i = 0; i < parms.length; i++) {int mod = parms[i].getModifiers() & Modifier.parameterModifiers();String modifiers = Modifier.toString(mod);String parmType = parms[i].getType().getSimpleName();String parmName = parms[i].getName();String temp = modifiers + " " + parmType + " " + parmName;if (temp.trim().length() == 0) {continue;}parmList.add(temp.trim());}return parmList;}public static ArrayList<String> getExceptionList(Executable exec) {ArrayList<String> exceptionList = new ArrayList<>();for (Class<?> c : exec.getExceptionTypes()) {exceptionList.add(c.getSimpleName());}return exceptionList;}public static String getModifiers(Executable exec) {int mod = exec.getModifiers();if (exec instanceof Method) {mod = mod & Modifier.methodModifiers();} else if (exec instanceof Constructor) {mod = mod & Modifier.constructorModifiers();}return Modifier.toString(mod);}
}
上面的代码生成以下结果。
