使用Java反射获取类的信息

  1/**
  2 * copied from core java volume 1 chapter 5 page 195<br>
  3 * class to analysis a java class via reflect
  4 *
  5 * @author wangy
  6 * @version 1.0
  7 * @date 2020/4/28 / 16:04
  8 */
  9@SuppressWarnings("rawtypes")
 10public class ReflectionTest {
 11    public static void main(String[] args) {
 12        String name;
 13        Scanner scanner = new Scanner(System.in);
 14        if (args.length > 0) {
 15            name = args[0];
 16        } else {
 17            System.out.println("Enter Class name(e.g. java.util.ArrayList)");
 18            name = scanner.next();
 19        }
 20        try {
 21            // print class name and super class name(if != Object)
 22            Class cls = Class.forName(name);
 23            Class superCls = cls.getSuperclass();
 24            String modifiers = Modifier.toString(cls.getModifiers());
 25            if (modifiers.length() > 0) {
 26                System.out.print(modifiers + " ");
 27            }
 28            System.out.print("class " + cls.getSimpleName());
 29            if (superCls != null && superCls != Object.class) {
 30                System.out.print(" extends " + superCls.getSimpleName());
 31            }
 32            System.out.print("{\n");
 33            printConstructors(cls);
 34            System.out.println();
 35            printMethods(cls);
 36            System.out.println();
 37            printFields(cls);
 38            System.out.println("}");
 39        } catch (Exception e) {
 40            e.printStackTrace();
 41        }
 42        scanner.close();
 43        System.exit(0);
 44    }
 45
 46    /**
 47     * print all constructors of a class
 48     *
 49     * @param cls
 50     */
 51    private static void printConstructors(Class cls) {
 52        Constructor[] constructors = cls.getDeclaredConstructors();
 53        for (Constructor c : constructors) {
 54            String cName = c.getDeclaringClass().getSimpleName();
 55            System.out.print("\t");
 56            String s = Modifier.toString(c.getModifiers());
 57            if (s.length() > 0) {
 58                System.out.print(s + " ");
 59            }
 60            System.out.print(cName + " (");
 61            //  parameters
 62            Class<?>[] pTypes = c.getParameterTypes();
 63            for (int i = 0; i < pTypes.length; i++) {
 64                if (i > 0) {
 65                    System.out.print(", ");
 66                }
 67                System.out.print(pTypes[i].getSimpleName());
 68            }
 69            System.out.print(");\n");
 70        }
 71    }
 72
 73    private static void printMethods(Class cls) {
 74        Method[] methods = cls.getDeclaredMethods();
 75        for (Method m : methods) {
 76            Class<?> r = m.getReturnType();
 77            String mName = m.getName();
 78            System.out.print("\t");
 79            String s = Modifier.toString(m.getModifiers());
 80            if (s.length() > 0) {
 81                System.out.print(s + " ");
 82            }
 83            System.out.print(r.getSimpleName() + " " + mName + "(");
 84            // print parameters
 85            Class<?>[] p = m.getParameterTypes();
 86            for (int i = 0; i < p.length; i++) {
 87                if (i > 0) {
 88                    System.out.print(", ");
 89                }
 90                System.out.print(p[i].getSimpleName());
 91            }
 92            System.out.print(");\n");
 93        }
 94    }
 95
 96    private static void printFields(Class cls) {
 97        Field[] fields = cls.getDeclaredFields();
 98        for (Field f : fields) {
 99            Class<?> fType = f.getType();
100            String fName = f.getName();
101            System.out.print("\t");
102            String s = Modifier.toString(f.getModifiers());
103            if (s.length() > 0) {
104                System.out.print(s + " ");
105            }
106            System.out.print(fType.getName() + " " + fName + ";\n");
107        }
108    }
109}