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2010-06-01T06:02:07Z

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в 18:01, 31 мая 2010

2010-05-31T18:01:43Z

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== Class Reflection: find out the constructor information ==



<source lang="java">

/* From http://java.sun.ru/docs/books/tutorial/index.html */
/*
* Copyright (c) 1995-1998 Sun Microsystems, Inc. All Rights Reserved.
*
* Permission to use, copy, modify, and distribute this software and its
* documentation for NON-COMMERCIAL purposes and without fee is hereby granted
* provided that this copyright notice appears in all copies. Please refer to
* the file "copyright.html" for further important copyright and licensing
* information.
*
* SUN MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF THE
* SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE IMPLIED
* WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR
* NON-INFRINGEMENT. SUN SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY
* LICENSEE AS A RESULT OF USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS
* DERIVATIVES.
*/
import java.awt.Rectangle;
import java.lang.reflect.Constructor;
public class SampleConstructor {
public static void main(String[] args) {
Rectangle r = new Rectangle();
showConstructors(r);
}
static void showConstructors(Object o) {
Class c = o.getClass();
Constructor[] theConstructors = c.getConstructors();
for (int i = 0; i < theConstructors.length; i++) {
System.out.print("( ");
Class[] parameterTypes = theConstructors[i].getParameterTypes();
for (int k = 0; k < parameterTypes.length; k++) {
String parameterString = parameterTypes[k].getName();
System.out.print(parameterString + " ");
}
System.out.println(")");
}
}
}

</source>



== Constructor Reflection ==



<source lang="java">

import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
public class ReflectionTest {
public static void main(String[] args) {
String name = "java.util.Date";
try {
Class cl = Class.forName(name);
Class supercl = cl.getSuperclass();
System.out.print("class " + name);
if (supercl != null && !supercl.equals(Object.class))
System.out.println(" extends " + supercl.getName());
System.out.print("Its constructors:");
printConstructors(cl);
System.out.println();
} catch (ClassNotFoundException e) {
System.out.println("Class not found.");
}
}
public static void printConstructors(Class cl) {
Constructor[] constructors = cl.getDeclaredConstructors();
for (int i = 0; i < constructors.length; i++) {
Constructor c = constructors[i];
Class[] paramTypes = c.getParameterTypes();
String name = c.getName();
System.out.print(Modifier.toString(c.getModifiers()));
System.out.print(" " + 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>



== Create object using Constructor object ==



<source lang="java">

import java.lang.reflect.Constructor;
public class Main {
public static void main(String[] args) throws Exception {
Class clazz = String.class;
Constructor constructor = clazz.getConstructor(new Class[] { String.class });
String object = (String) constructor.newInstance(new Object[] { "Hello World!" });
System.out.println("String = " + object);
constructor = clazz.getConstructor(new Class[] { StringBuilder.class });
object = (String) constructor
.newInstance(new Object[] { new StringBuilder("Hello Universe!") });
System.out.println("String = " + object);
}
}

</source>



== Creating an Object Using a Constructor Object ==



<source lang="java">

import java.lang.reflect.Constructor;
public class Main {
public static void main(String[] argv) throws Exception {
Constructor con = java.awt.Point.class.getConstructor(new Class[] { int.class, int.class });
java.awt.Point obj = (java.awt.Point) con.newInstance(new Object[] { new Integer(123),
new Integer(123) });
}
}

</source>



== Get all construtors from a class ==



<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 args[]) throws Exception {
Class c = Class.forName("MyClass");
System.out.println("Constructors:");
Constructor constructors[] = c.getDeclaredConstructors();
for (Constructor cons : constructors)
System.out.println(" " + cons);
}
}
class MyClass {
private int count;
MyClass(int c) {
count = c;
}
MyClass() {
count = 0;
}
void setCount(int c) {
count = c;
}
int getCount() {
return count;
}
void showcount() {
System.out.println("count is " + count);
}
}

</source>



== Get constructors of a class object ==



<source lang="java">

import java.lang.reflect.Constructor;
public class Main {
public static void main(String[] args) throws Exception {
Class clazz = String.class;
Constructor[] constructors = clazz.getDeclaredConstructors();
for (Constructor constructor : constructors) {
String name = constructor.getName();
System.out.println("Constructor name= " + name);
Class[] paramterTypes = constructor.getParameterTypes();
for (Class c : paramterTypes) {
System.out.println("Param type name = " + c.getName());
}
}
Constructor constructor = String.class.getConstructor(new Class[] { String.class });
System.out.println("Constructor = " + constructor.getName());
}
}

</source>



== Getting a Constructor of a Class Object: By obtaining a list of all Constructors object ==



<source lang="java">

import java.lang.reflect.Constructor;
public class Main {
public static void main(String[] argv) throws Exception {
Constructor[] cons = String.class.getDeclaredConstructors();
for (int i = 0; i < cons.length; i++) {
Class[] paramTypes = cons[i].getParameterTypes();
System.out.println(cons[i]);
}
}
}

</source>



== Getting a Constructor of a Class Object: By obtaining a particular Constructor object. ==



<source lang="java">

import java.lang.reflect.Constructor;
public class Main {
public static void main(String[] argv) throws Exception {
Constructor con = java.awt.Point.class.getConstructor(new Class[] { int.class, int.class });
System.out.println(con);
}
}

</source>



== Has Declared Constructor ==



<source lang="java">

import java.lang.reflect.Constructor;
public class ReflectionUtils {
public static boolean hasDeclaredConstructor(Class targetClass, Class[] partypes) {
Constructor constructor = null;
try {
constructor = targetClass.getConstructor(partypes);
}catch (Exception e) {
e.printStackTrace();
}
return constructor != null;
}

}

</source>



== Object Reflection: invoke constructor with parameters ==



<source lang="java">

/* From http://java.sun.ru/docs/books/tutorial/index.html */
/*
* Copyright (c) 1995-1998 Sun Microsystems, Inc. All Rights Reserved.
*
* Permission to use, copy, modify, and distribute this software and its
* documentation for NON-COMMERCIAL purposes and without fee is hereby granted
* provided that this copyright notice appears in all copies. Please refer to
* the file "copyright.html" for further important copyright and licensing
* information.
*
* SUN MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF THE
* SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE IMPLIED
* WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR
* NON-INFRINGEMENT. SUN SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY
* LICENSEE AS A RESULT OF USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS
* DERIVATIVES.
*/
import java.awt.Rectangle;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
public class SampleInstance {
public static void main(String[] args) {
Rectangle rectangle;
Class rectangleDefinition;
Class[] intArgsClass = new Class[] { int.class, int.class };
Integer height = new Integer(12);
Integer width = new Integer(34);
Object[] intArgs = new Object[] { height, width };
Constructor intArgsConstructor;
try {
rectangleDefinition = Class.forName("java.awt.Rectangle");
intArgsConstructor = rectangleDefinition
.getConstructor(intArgsClass);
rectangle = (Rectangle) createObject(intArgsConstructor, intArgs);
} catch (ClassNotFoundException e) {
System.out.println(e);
} catch (NoSuchMethodException e) {
System.out.println(e);
}
}
public static Object createObject(Constructor constructor,
Object[] arguments) {
System.out.println("Constructor: " + constructor.toString());
Object object = null;
try {
object = constructor.newInstance(arguments);
System.out.println("Object: " + object.toString());
return object;
} catch (InstantiationException e) {
System.out.println(e);
} catch (IllegalAccessException e) {
System.out.println(e);
} catch (IllegalArgumentException e) {
System.out.println(e);
} catch (InvocationTargetException e) {
System.out.println(e);
}
return object;
}
}

</source>



== Passing a parameter to the constructor and calling a method dynamically ==



<source lang="java">

public class Main {
public static void main(String args[]) throws Exception{
String name = "java.lang.String";
String methodName = "toLowerCase";
Class cl = Class.forName(name);
java.lang.reflect.Constructor constructor = cl.getConstructor(new Class[] { String.class });
Object invoker = constructor.newInstance(new Object[] { "AAA" });
Class arguments[] = new Class[] {};
java.lang.reflect.Method objMethod = cl.getMethod(methodName, arguments);
Object result = objMethod.invoke(invoker, (Object[]) arguments);
System.out.println(result);
}
}

</source>

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Admin: 1 версия

в 18:01, 31 мая 2010