JAVA反射

  1 /**
  2    @version 1.1 2004-02-21
  3    @author Cay Horstmann
  4 */
  5 
  6 import java.util.*;
  7 import java.lang.reflect.*;
  8 
  9 public class ReflectionTest
 10 {  
 11    public static void main(String[] args)
 12    {  
 13       // read class name from command line args or user input
 14       String name;
 15       if (args.length > 0) 
 16          name = args[0];
 17       else 
 18       {
 19          Scanner in = new Scanner(System.in);
 20          System.out.println("Enter class name (e.g. java.util.Date): ");
 21          name = in.next();
 22       }
 23 
 24       try
 25       {  
 26          // print class name and superclass name (if != Object)
 27          Class cl = Class.forName(name);
 28          Class supercl = cl.getSuperclass();
 29          System.out.print("class " + name);
 30          if (supercl != null && supercl != Object.class)
 31             System.out.print(" extends " + supercl.getName());
 32 
 33          System.out.print("\n{\n");
 34          printConstructors(cl);
 35          System.out.println();
 36          printMethods(cl);
 37          System.out.println();
 38          printFields(cl);
 39          System.out.println("}");
 40       }
 41       catch(ClassNotFoundException e) { e.printStackTrace(); }
 42       System.exit(0);
 43    }
 44 
 45    /**
 46       Prints all constructors of a class
 47       @param cl a class
 48     */
 49    public static void printConstructors(Class cl)
 50    {  
 51       Constructor[] constructors = cl.getDeclaredConstructors();
 52 
 53       for (Constructor c : constructors)
 54       {           
 55          String name = c.getName();
 56          System.out.print("   " + Modifier.toString(c.getModifiers()));
 57          System.out.print(" " + name + "(");
 58 
 59          // print parameter types
 60          Class[] paramTypes = c.getParameterTypes();
 61          for (int j = 0; j < paramTypes.length; j++)
 62          {  
 63             if (j > 0) System.out.print(", ");
 64             System.out.print(paramTypes[j].getName());
 65          }
 66          System.out.println(");");
 67       }
 68    }
 69 
 70    /**
 71       Prints all methods of a class
 72       @param cl a class
 73     */
 74    public static void printMethods(Class cl)
 75    {  
 76       Method[] methods = cl.getDeclaredMethods();
 77 
 78       for (Method m : methods)
 79       {  
 80          Class retType = m.getReturnType();
 81          String name = m.getName();
 82 
 83          // print modifiers, return type and method name
 84          System.out.print("   " + Modifier.toString(m.getModifiers()));
 85          System.out.print(" " + retType.getName() + " " + name + "(");
 86 
 87          // print parameter types
 88          Class[] paramTypes = m.getParameterTypes();
 89          for (int j = 0; j < paramTypes.length; j++)
 90          {  
 91             if (j > 0) System.out.print(", ");
 92             System.out.print(paramTypes[j].getName());
 93          }
 94          System.out.println(");");
 95       }
 96    }
 97 
 98    /**
 99       Prints all fields of a class
100       @param cl a class
101     */
102    public static void printFields(Class cl)
103    {  
104       Field[] fields = cl.getDeclaredFields();
105 
106       for (Field f : fields)
107       {  
108          Class type = f.getType();
109          String name = f.getName();
110          System.out.print("   " + Modifier.toString(f.getModifiers()));
111          System.out.println(" " + type.getName() + " " + name + ";");
112       }
113    }
114 }