Java by API/java.lang.reflect/Method

Содержание

1 Method: getAnnotation(Class < MyAnno > annotationClass)
2 Method: getExceptionTypes()
3 Method: getModifiers()
4 Method: getName()
5 Method: getParameterTypes()
6 Method: getReturnType()
7 Method: invoke(Object obj, Object... args)
8 Method: setAccessible(boolean flag)
9 Method: toGenericString()
10 Method: toString()

Method: getAnnotation(Class < MyAnno > annotationClass)

   <source lang="java">

import java.lang.annotation.Retention; import java.lang.annotation.RetentionPolicy; import java.lang.reflect.Method; @Retention(RetentionPolicy.RUNTIME) @interface MyAnno {

 String str();
 int val();

} public class MainClass {

 @MyAnno(str = "Annotation Example", val = 100)
 public static void myMeth() {
   MainClass ob = new MainClass();
   try {
     Class c = ob.getClass();
     Method m = c.getMethod("myMeth");
     MyAnno anno = m.getAnnotation(MyAnno.class);
     System.out.println(anno.str() + " " + anno.val());
   } catch (NoSuchMethodException exc) {
     System.out.println("Method Not Found.");
   }
 }
 public static void main(String args[]) {
   myMeth();
 }

}

 </source>

Method: getExceptionTypes()

   <source lang="java">

import java.lang.reflect.Constructor; import java.lang.reflect.Field; import java.lang.reflect.Member; import java.lang.reflect.Method; import java.lang.reflect.Modifier; public class Main{

 public static void main(String[] args) throws ClassNotFoundException {
   Class c = Class.forName(args[0]);
   print_class(c);
 }
 public static void print_class(Class c) {
   if (c.isInterface()) {
     System.out.print(Modifier.toString(c.getModifiers()) + " " + typename(c));
   } else if (c.getSuperclass() != null) {
     System.out.print(Modifier.toString(c.getModifiers()) + " class " + typename(c) + " extends "
         + typename(c.getSuperclass()));
   } else {
     System.out.print(Modifier.toString(c.getModifiers()) + " class " + typename(c));
   }
   Class[] interfaces = c.getInterfaces();
   if ((interfaces != null) && (interfaces.length > 0)) {
     if (c.isInterface())
       System.out.print(" extends ");
     else
       System.out.print(" implements ");
     for (int i = 0; i < interfaces.length; i++) {
       if (i > 0)
         System.out.print(", ");
       System.out.print(typename(interfaces[i]));
     }
   }
   System.out.println(" {"); 
   Constructor[] constructors = c.getDeclaredConstructors();
   for (int i = 0; i < constructors.length; i++)
     print_method_or_constructor(constructors[i]);
   Field[] fields = c.getDeclaredFields();
   for (int i = 0; i < fields.length; i++){
     print_field(fields[i]);
   }
   Method[] methods = c.getDeclaredMethods();
   for (int i = 0; i < methods.length; i++)
     print_method_or_constructor(methods[i]);
   System.out.println("}");
 }
 public static String typename(Class t) {
   String brackets = "";
   while (t.isArray()) {
     brackets += "[]";
     t = t.getComponentType();
   }
   String name = t.getName();
   int pos = name.lastIndexOf(".");
   if (pos != -1)
     name = name.substring(pos + 1);
   return name + brackets;
 }
 public static String modifiers(int m) {
   if (m == 0)
     return "";
   else
     return Modifier.toString(m) + " ";
 }
 public static void print_field(Field f) {
   System.out.println("  " + modifiers(f.getModifiers()) + typename(f.getType()) + " "
       + f.getName() + ";");
 }
 public static void print_method_or_constructor(Member member) {
   Class returntype = null, parameters[], exceptions[];
   if (member instanceof Method) {
     Method m = (Method) member;
     returntype = m.getReturnType();
     parameters = m.getParameterTypes();
     exceptions = m.getExceptionTypes();
     System.out.print("  " + modifiers(member.getModifiers()) + typename(returntype) + " "
         + member.getName() + "(");
   } else {
     Constructor c = (Constructor) member;
     parameters = c.getParameterTypes();
     exceptions = c.getExceptionTypes();
     System.out.print("  " + modifiers(member.getModifiers()) + typename(c.getDeclaringClass())
         + "(");
   }
   for (int i = 0; i < parameters.length; i++) {
     if (i > 0)
       System.out.print(", ");
     System.out.print(typename(parameters[i]));
   }
   System.out.print(")");
   if (exceptions.length > 0)
     System.out.print(" throws ");
   for (int i = 0; i < exceptions.length; i++) {
     if (i > 0)
       System.out.print(", ");
     System.out.print(typename(exceptions[i]));
   }
   System.out.println(";");
 }

}

 </source>

Method: getModifiers()

   <source lang="java">

/*

* Output:

Public Methods:

a1
a2
* */

import java.lang.reflect.Method; import java.lang.reflect.Modifier; public class MainClass {

 public static void main(String args[]) {
   try {
     MyClass a = new MyClass();
     Class c = a.getClass();
     System.out.println("Public Methods:");
     Method methods[] = c.getDeclaredMethods();
     for (int i = 0; i < methods.length; i++) {
       int modifiers = methods[i].getModifiers();
       if (Modifier.isPublic(modifiers)) {
         System.out.println(" " + methods[i].getName());
       }
     }
   } catch (Exception e) {
     System.out.println("Exception: " + e);
   }
 }

} class MyClass {

 public void a1() {
 }
 public void a2() {
 }
 protected void a3() {
 }
 private void a4() {
 }

}

 </source>

Method: getName()

   <source lang="java">

import java.lang.reflect.Method; import java.lang.reflect.Modifier; public class Main {

 public static void main(String[] args) {
   String name = "java.util.Date";
   try {
     Class cl = Class.forName(name);
     System.out.println("class " + name);
     System.out.println("Its methods:");
     printMethods(cl);
     System.out.println();
   } catch (ClassNotFoundException e) {
     System.out.println("Class not found.");
   }
 }
 public static void printMethods(Class cl) {
   Method[] methods = cl.getDeclaredMethods();
   for (int i = 0; i < methods.length; i++) {
     Method m = methods[i];
     Class retType = m.getReturnType();
     Class[] paramTypes = m.getParameterTypes();
     String name = m.getName();
     System.out.print(Modifier.toString(m.getModifiers()));
     System.out.print(" " + retType.getName() + " " + name + "(");
     for (int j = 0; j < paramTypes.length; j++) {
       if (j > 0)
         System.out.print(", ");
       System.out.print(paramTypes[j].getName());
     }
     System.out.println(");");
   }
 }

}

 </source>

Method: getParameterTypes()

   <source lang="java">

import java.lang.reflect.Constructor; import java.lang.reflect.Field; import java.lang.reflect.Member; import java.lang.reflect.Method; import java.lang.reflect.Modifier; public class Main{

 public static void main(String[] args) throws ClassNotFoundException {
   Class c = Class.forName(args[0]);
   print_class(c);
 }
 public static void print_class(Class c) {
   if (c.isInterface()) {
     System.out.print(Modifier.toString(c.getModifiers()) + " " + typename(c));
   } else if (c.getSuperclass() != null) {
     System.out.print(Modifier.toString(c.getModifiers()) + " class " + typename(c) + " extends "
         + typename(c.getSuperclass()));
   } else {
     System.out.print(Modifier.toString(c.getModifiers()) + " class " + typename(c));
   }
   Class[] interfaces = c.getInterfaces();
   if ((interfaces != null) && (interfaces.length > 0)) {
     if (c.isInterface())
       System.out.print(" extends ");
     else
       System.out.print(" implements ");
     for (int i = 0; i < interfaces.length; i++) {
       if (i > 0)
         System.out.print(", ");
       System.out.print(typename(interfaces[i]));
     }
   }
   System.out.println(" {"); 
   Constructor[] constructors = c.getDeclaredConstructors();
   for (int i = 0; i < constructors.length; i++)
     print_method_or_constructor(constructors[i]);
   Field[] fields = c.getDeclaredFields();
   for (int i = 0; i < fields.length; i++){
     print_field(fields[i]);
   }
   Method[] methods = c.getDeclaredMethods();
   for (int i = 0; i < methods.length; i++)
     print_method_or_constructor(methods[i]);
   System.out.println("}");
 }
 public static String typename(Class t) {
   String brackets = "";
   while (t.isArray()) {
     brackets += "[]";
     t = t.getComponentType();
   }
   String name = t.getName();
   int pos = name.lastIndexOf(".");
   if (pos != -1)
     name = name.substring(pos + 1);
   return name + brackets;
 }
 public static String modifiers(int m) {
   if (m == 0)
     return "";
   else
     return Modifier.toString(m) + " ";
 }
 public static void print_field(Field f) {
   System.out.println("  " + modifiers(f.getModifiers()) + typename(f.getType()) + " "
       + f.getName() + ";");
 }
 public static void print_method_or_constructor(Member member) {
   Class returntype = null, parameters[], exceptions[];
   if (member instanceof Method) {
     Method m = (Method) member;
     returntype = m.getReturnType();
     parameters = m.getParameterTypes();
     exceptions = m.getExceptionTypes();
     System.out.print("  " + modifiers(member.getModifiers()) + typename(returntype) + " "
         + member.getName() + "(");
   } else {
     Constructor c = (Constructor) member;
     parameters = c.getParameterTypes();
     exceptions = c.getExceptionTypes();
     System.out.print("  " + modifiers(member.getModifiers()) + typename(c.getDeclaringClass())
         + "(");
   }
   for (int i = 0; i < parameters.length; i++) {
     if (i > 0)
       System.out.print(", ");
     System.out.print(typename(parameters[i]));
   }
   System.out.print(")");
   if (exceptions.length > 0)
     System.out.print(" throws ");
   for (int i = 0; i < exceptions.length; i++) {
     if (i > 0)
       System.out.print(", ");
     System.out.print(typename(exceptions[i]));
   }
   System.out.println(";");
 }

}

 </source>

Method: getReturnType()

   <source lang="java">

import java.lang.reflect.Constructor; import java.lang.reflect.Field; import java.lang.reflect.Member; import java.lang.reflect.Method; import java.lang.reflect.Modifier; public class Main{

 public static void main(String[] args) throws ClassNotFoundException {
   Class c = Class.forName(args[0]);
   print_class(c);
 }
 public static void print_class(Class c) {
   if (c.isInterface()) {
     System.out.print(Modifier.toString(c.getModifiers()) + " " + typename(c));
   } else if (c.getSuperclass() != null) {
     System.out.print(Modifier.toString(c.getModifiers()) + " class " + typename(c) + " extends "
         + typename(c.getSuperclass()));
   } else {
     System.out.print(Modifier.toString(c.getModifiers()) + " class " + typename(c));
   }
   Class[] interfaces = c.getInterfaces();
   if ((interfaces != null) && (interfaces.length > 0)) {
     if (c.isInterface())
       System.out.print(" extends ");
     else
       System.out.print(" implements ");
     for (int i = 0; i < interfaces.length; i++) {
       if (i > 0)
         System.out.print(", ");
       System.out.print(typename(interfaces[i]));
     }
   }
   System.out.println(" {"); 
   Constructor[] constructors = c.getDeclaredConstructors();
   for (int i = 0; i < constructors.length; i++)
     print_method_or_constructor(constructors[i]);
   Field[] fields = c.getDeclaredFields();
   for (int i = 0; i < fields.length; i++){
     print_field(fields[i]);
   }
   Method[] methods = c.getDeclaredMethods();
   for (int i = 0; i < methods.length; i++)
     print_method_or_constructor(methods[i]);
   System.out.println("}");
 }
 public static String typename(Class t) {
   String brackets = "";
   while (t.isArray()) {
     brackets += "[]";
     t = t.getComponentType();
   }
   String name = t.getName();
   int pos = name.lastIndexOf(".");
   if (pos != -1)
     name = name.substring(pos + 1);
   return name + brackets;
 }
 public static String modifiers(int m) {
   if (m == 0)
     return "";
   else
     return Modifier.toString(m) + " ";
 }
 public static void print_field(Field f) {
   System.out.println("  " + modifiers(f.getModifiers()) + typename(f.getType()) + " "
       + f.getName() + ";");
 }
 public static void print_method_or_constructor(Member member) {
   Class returntype = null, parameters[], exceptions[];
   if (member instanceof Method) {
     Method m = (Method) member;
     returntype = m.getReturnType();
     parameters = m.getParameterTypes();
     exceptions = m.getExceptionTypes();
     System.out.print("  " + modifiers(member.getModifiers()) + typename(returntype) + " "
         + member.getName() + "(");
   } else {
     Constructor c = (Constructor) member;
     parameters = c.getParameterTypes();
     exceptions = c.getExceptionTypes();
     System.out.print("  " + modifiers(member.getModifiers()) + typename(c.getDeclaringClass())
         + "(");
   }
   for (int i = 0; i < parameters.length; i++) {
     if (i > 0)
       System.out.print(", ");
     System.out.print(typename(parameters[i]));
   }
   System.out.print(")");
   if (exceptions.length > 0)
     System.out.print(" throws ");
   for (int i = 0; i < exceptions.length; i++) {
     if (i > 0)
       System.out.print(", ");
     System.out.print(typename(exceptions[i]));
   }
   System.out.println(";");
 }

}

 </source>

Method: invoke(Object obj, Object... args)

   <source lang="java">

import java.lang.reflect.InvocationTargetException; import java.lang.reflect.Method; public class MainClass {

 public static void main(String args[]) throws Exception {
   try {
     Class c = Class.forName("java.text.NumberFormat");
     Method m = c.getMethod("getInstance");
     Object ret = m.invoke(null);
     System.out.println("Results: " + ret);
   } catch (ClassNotFoundException e) {
     System.out.println("Class.forName(  ) can"t find the class");
   } catch (NoSuchMethodException e2) {
     System.out.println("method doesn"t exist");
   } catch (IllegalAccessException e3) {
     System.out.println("no permission to invoke that method");
   } catch (InvocationTargetException e) {
     System.out.println("an exception ocurred while invoking that method");
     System.out.println("Method threw an: " + e.getTargetException());
   }
 }

}

 </source>

Method: setAccessible(boolean flag)

   <source lang="java">

import java.lang.reflect.Constructor; import java.lang.reflect.Field; import java.lang.reflect.Method; public class Main {

 public static void main(String[] argv) throws Exception {
   Class cls = java.lang.String.class;
   Method method = cls.getMethods()[0];
   Field field = cls.getFields()[0];
   Constructor constructor = cls.getConstructors()[0];
   field.setAccessible(true);
   constructor.setAccessible(true);
   method.setAccessible(true);
 }

}

 </source>

Method: toGenericString()

   <source lang="java">

/*

* Copyright (c) 1995 - 2008 Sun Microsystems, Inc.  All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
*   - Redistributions of source code must retain the above copyright
*     notice, this list of conditions and the following disclaimer.
*
*   - Redistributions in binary form must reproduce the above copyright
*     notice, this list of conditions and the following disclaimer in the
*     documentation and/or other materials provided with the distribution.
*
*   - Neither the name of Sun Microsystems nor the names of its
*     contributors may be used to endorse or promote products derived
*     from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
* IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

import static java.lang.System.out; import java.lang.reflect.Method; import java.lang.reflect.Type; public class Main {

 private static final String fmt = "%24s: %s%n";
 // for the morbidly curious
 <E extends RuntimeException> void genericThrow() throws E {
 }
 public static void main(String... args) throws Exception {
   Class<?> c = Class.forName(args[0]);
   Method[] allMethods = c.getDeclaredMethods();
   for (Method m : allMethods) {
     if (!m.getName().equals(args[1])) {
       continue;
     }
     out.format("%s%n", m.toGenericString());
     Class<?>[] xType = m.getExceptionTypes();
     Type[] gxType = m.getGenericExceptionTypes();
     for (int i = 0; i < xType.length; i++) {
       out.format(fmt, "ExceptionType", xType[i]);
       out.format(fmt, "GenericExceptionType", gxType[i]);
     }
   }
 }

}

 </source>

Method: toString()

   <source lang="java">

import java.lang.reflect.Method; /**

* Demonstrates how to get specific method information.
* 
* @author 
* @version $Revision: 1.3 $
*/

public class Main {

 public static void main(final String[] args) {
   final Method byteValueMeth;
   final Method waitMeth;
   final Method waitDetailMeth;
   try {
     byteValueMeth = Number.class.getMethod("byteValue", null);
     waitMeth = Number.class.getMethod("wait", new Class[] {});
     waitDetailMeth = Number.class.getMethod("wait", new Class[] { long.class, int.class });
   } catch (final NoSuchMethodException ex) {
     throw new RuntimeException(ex);
   }
   System.out.println("byteValueMeth = " + byteValueMeth.toString());
   System.out.println("waitMeth = " + waitMeth.toString());
   System.out.println("waitDetailMeth = " + waitDetailMeth.toString());
 }

}

 </source>

Java by API/java.lang.reflect/Method

Содержание

Method: getAnnotation(Class < MyAnno > annotationClass)

Method: getExceptionTypes()

Method: getModifiers()

Method: getName()

Method: getParameterTypes()

Method: getReturnType()

Method: invoke(Object obj, Object... args)

Method: setAccessible(boolean flag)

Method: toGenericString()

Method: toString()

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