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  • Tutorial Refleksi Java: Buat Java POJO menggunakan API Refleksi untuk mendapatkan ClassName, DeclaredFields, ObjectType, SuperType, dan Lainnya…

Tutorial Refleksi Java: Buat Java POJO menggunakan API Refleksi untuk mendapatkan ClassName, DeclaredFields, ObjectType, SuperType, dan Lainnya…

Diterbitkan: 2019-06-10
Contoh Java Reflection API - Total 10 Contoh- Tips Crunchify

Cara terprogram terbaik untuk mendapatkan semua Bidang Kelas yang Dideklarasikan di Java menggunakan API Refleksi

Dalam tutorial ini saya akan menulis POJO Java sederhana pertama dan akan melakukan semua Contoh Refleksi Java pada POJO. Anda pasti pernah mendengar istilah POJO. Apa itu Plain Old Java Object ?

Juga jika Anda memiliki pertanyaan di bawah ini maka Anda berada di lokasi yang tepat:

  • java – Bagaimana cara membuat POJO?
  • java – Buat kelas POJO sederhana
  • Objek Java lama biasa (POJO) di Jawa
  • Pengenalan POJO (Objek Jawa Kuno Biasa)
  • Merancang kelas POJO
  • Buat Orang kelas POJO Java ke-1

POJO hanyalah Java Bean tua biasa dengan batasan dihapus. Java Beans harus memenuhi persyaratan berikut:

  1. Ikuti konvensi Bean dari getFoo (atau isFoo untuk boolean) dan metode setFoo untuk atribut yang dapat diubah bernama foo; tinggalkan setFoo jika foo tidak dapat diubah.
  2. Konstruktor no-arg default
  3. Harus mengimplementasikan java.io.Serializable

POJO tidak mengamanatkan semua ini. Seperti namanya: objek yang dikompilasi di bawah JDK dapat dianggap sebagai Objek Java Lama Biasa.

Tidak ada server aplikasi, tidak ada kelas dasar, tidak ada antarmuka yang diperlukan untuk digunakan.

Mari kita buat kelas POJO bernama CrunchifyPOJO.

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package crunchify . com . tutorials ;
 
/**
* @author Crunchify.com Simple POJO Example
*/
 
public class CrunchifyPOJO {
 
public String name ;
protected String webAddress ;
public String email ;
protected int zip ;
 
public CrunchifyPOJO ( ) {
name = "Crunchify.com" ;
webAddress = "https://crunchify.com" ;
email = "[email protected]" ;
}
 
// ==========================================================
// Create a Setters and Getters for all variables
// ==========================================================
 
public String getName ( ) {
return name ;
}
 
public void setName ( String name ) {
this . name = name ;
}
 
protected String getWebAddress ( ) {
return webAddress ;
}
 
protected void setWebAddress ( String webAddress ) {
this . webAddress = webAddress ;
}
 
public String getEmail ( ) {
return email ;
}
 
public void setEmail ( String email ) {
this . email = email ;
}
 
protected int getZip ( ) {
return zip ;
}
 
protected void setZip ( int zip ) {
this . zip = zip ;
}
 
public void thisIsCrunchifyReflection ( ) {
System . out . println ( "- Hey This is Crunchify's Refection API tutorials. More than 400 Tutorials on Crunchify.com" ) ;
}
 
// ==========================================================
// Create a String description of a Crunchify credentials
// ==========================================================
 
public String toString ( ) {
String result = "Name: " + getName ( ) + "\n" ;
result += "WebAddress: " + getWebAddress ( ) + "\n" ;
result += "email: " + getEmail ( ) + "\n" ;
result += "zip: " + getZip ( ) + "\n" ;
return result ;
}
 
public static void main ( String [ ] args ) {
 
// Create and print a CrunchifyPOJO object ...
CrunchifyPOJO crunchify = new CrunchifyPOJO ( ) ;
crunchify . setName ( "Crunchify.com" ) ;
crunchify . setWebAddress ( "https://crunchify.com" ) ;
crunchify . setEmail ( "[email protected]" ) ;
crunchify . setZip ( 95124 ) ;
System . out . println ( crunchify ) ;
}
}

Hasil:

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Name : Crunchify . com
WebAddress : https : //crunchify.com
email : test @ crunchify . com
zip : 95124
Refleksi Java - Tutorial Crunchify

Sekarang mari kita membuat Java Reflection's Example berdasarkan POJO ini.

Lihatlah di bawah ini Contoh kelas CrunchifyReflectionTutorial.java yang mencakup total 9 contoh Java Reflection API yang berbeda:

Apakah Anda menjalankan program Java?

Bagaimana jika Anda ingin memeriksa kelas, antarmuka, bidang, dan metode saat runtime, tanpa mengetahui nama kelas, metode, dll. pada waktu kompilasi. Nah, dengan bantuan Reflection itu sangat mudah dilakukan.

Refleksi biasanya digunakan oleh program yang memerlukan kemampuan untuk memeriksa atau memodifikasi perilaku runtime dari aplikasi yang berjalan di mesin virtual Java.

Mengenai Refleksi Java Jika Anda memiliki pertanyaan di bawah ini, maka Anda berada di lokasi yang tepat:

  • Tutorial Refleksi Java untuk Kelas, Metode, Bidang
  • Pemuatan Kelas Dinamis menggunakan Java Reflection API
  • Lihatlah lebih dalam pada Java Reflection API
  • refleksi java api – Cara membuat objek menggunakan objek Konstruktor
  • refleksi – Bagaimana cara memanggil metode Java
  • Cara menggunakan Refleksi untuk memanggil metode Java saat runtime
  • java refleksi memanggil metode tanpa argumen
  • Cara mendapatkan Nama Kelas, CanonicalName dan SimpleName
  • Mari kita cari tahu apakah objek kelas mewakili kelas Array
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package crunchify . com . tutorials ;
 
import java . lang . reflect . Constructor ;
import java . lang . reflect . Field ;
import java . lang . reflect . Method ;
 
/**
* @author Crunchify.com
*
*/
 
public class CrunchifyReflectionTutorial {
public static void main ( String [ ] args ) {
CrunchifyPOJO crunchify = new CrunchifyPOJO ( ) ;
System . out . println ( "Crunchify Object: ====================\n" + crunchify ) ;
 
// How to find out the Object belongs to which class?
Class <? > clazz = crunchify . getClass ( ) ;
 
// Example 1: ==================== How to get the Class's Name,
// CanonicalName and SimpleName?
String clazzName = clazz . getName ( ) ;
String clazzCanonicalName = clazz . getCanonicalName ( ) ;
String clazzSimpleName = clazz . getSimpleName ( ) ;
 
System . out . println ( "How to get the Class's Name, CanonicalName and SimpleName? ==================== Example 1" ) ;
System . out . println ( "1. clazzName: " + clazzName + ", \n2. clazzCanonicalName: " + clazzCanonicalName
+ ", \n3. clazzSimpleName: " + clazzSimpleName + "\n" ) ;
 
// Example 2: ==================== Let's find out if class object
// represents an Array class
int [ ] [ ] crunchifyArr = { { 1 , 1 } , { 2 , 1 } } ;
Class <? extends int [ ] [ ] > arrClazz = crunchifyArr . getClass ( ) ;
System . out . println ( "Let's find out if class object represents an Array class ==================== Example 2" ) ;
if ( arrClazz . isArray ( ) ) {
System . out . println ( "- " + arrClazz . getSimpleName ( ) + " is an array class.\n" ) ;
} else {
System . out . println ( "- " + clazz . getSimpleName ( ) + " is not an array class.\n" ) ;
}
 
// Example 3: ==================== Let's find out Object's Type
Double crunchifyDouble = 11.1 ;
System . out . println ( "Let's find out Object's Type ==================== Example 3" ) ;
System . out . println ( "- 11.1 is of Type: " + crunchifyDouble . getClass ( ) . getName ( ) + "\n" ) ;
 
// Example 4: ==================== How to get SuperClass
System . out . println ( "How to get SuperClass ==================== Example 4" ) ;
System . out . println ( "1. Superclass of crunchify: " + crunchify . getClass ( ) . getSuperclass ( )
+ "\n2. Superclass of crunchifyDouble: " + crunchifyDouble . getClass ( ) . getSuperclass ( ) + "\n" ) ;
 
// Example 5: ==================== How to check if class is Primitive
// Type of not?
System . out . println ( "How to check if class is Primitive Type of not? ==================== Example 5" ) ;
System . out . println ( "1. Is 'int' a Prmitive Type: " + int . class . isPrimitive ( ) ) ;
System . out . println ( "2. Is 'String' a Prmitive Type: " + String . class . isPrimitive ( ) ) ;
System . out . println ( "3. Is 'double' a Prmitive Type: " + double . class . isPrimitive ( ) ) ;
 
// Example 6: ==================== How to create an object using
// Constructor object?
// A constructor reflection to create a string object by calling
// String(String) and String(StringBuilder) constructors.
Class < String > clazzString = String . class ;
System . out . println ( "\nHow to create object using Constructor object? ==================== Example 6" ) ;
try {
Constructor <? > constructor = clazzString . getConstructor ( new Class [ ] { String . class } ) ;
String object = ( String ) constructor . newInstance ( new Object [ ] { "Hello World!" } ) ;
System . out . println ( "1. String.class = " + object ) ;
 
constructor = clazzString . getConstructor ( new Class [ ] { StringBuilder . class } ) ;
object = ( String ) constructor . newInstance ( new Object [ ] { new StringBuilder ( "Hello Universe!" ) } ) ;
System . out . println ( "2. StringBuilder.class = " + object ) ;
} catch ( Exception e ) {
e . printStackTrace ( ) ;
}
 
// Example 7: ==================== How to get constructors of a class
// object?
System . out . println ( "\nHow to get constructors of a class object ==================== Example 7" ) ;
try {
Constructor <? extends CrunchifyPOJO > constructor = crunchify . getClass ( ) . getConstructor ( ) ;
System . out . println ( "- Constructor = " + constructor . getName ( ) ) ;
} catch ( NoSuchMethodException e ) {
e . printStackTrace ( ) ;
}
 
// Example 8: ==================== How to get field of a class object
try {
System . out . println ( "\nHow to get field of a class object ==================== Example 8" ) ;
Field [ ] methods = clazz . getFields ( ) ;
for ( Field temp : methods ) {
System . out . println ( "- " + temp . getName ( ) ) ;
}
 
} catch ( Exception e ) {
e . printStackTrace ( ) ;
}
 
// Example 9: ==================== How to invoke a method using Method
// class?
try {
System . out . println ( "\nHow to invoke a method using Method class ==================== Example 9" ) ;
Class <? > c = Class . forName ( "crunchify.com.tutorials.CrunchifyPOJO" ) ;
Object obj = c . newInstance ( ) ;
Method method = c . getDeclaredMethod ( "thisIsCrunchifyReflection" ) ;
method . invoke ( obj ) ;
} catch ( Exception e ) {
 
System . out . println ( e ) ;
}
 
// Example 10: ==================== get all Declared Class Fields
Field [ ] crunchifyFields = CrunchifyPOJO . class . getDeclaredFields ( ) ;
System . out . println ( "\nget all Declared Class Fields ==================== Example 10" ) ;
for ( Field field : crunchifyFields ) {
Class < ? > type = field . getType ( ) ;
System . out . println ( "field name : " + field . getName ( ) + " , type : " + type ) ;
}
}
 
}

Hasil:

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Crunchify Object : ====================
Name : Crunchify . com
WebAddress : https : //crunchify.com
email : test @ crunchify . com
zip : 0
 
How to get the Class 's Name, CanonicalName and SimpleName? ==================== Example 1
1. clazzName: crunchify.com.tutorials.CrunchifyPOJO,
2. clazzCanonicalName: crunchify.com.tutorials.CrunchifyPOJO,
3. clazzSimpleName: CrunchifyPOJO
 
Let' s find out if class object represents an Array class ==================== Example 2
- int [ ] [ ] is an array class .
 
Let 's find out Object' s Type ==================== Example 3
- 11.1 is of Type : java . lang . Double
 
How to get SuperClass ==================== Example 4
1. Superclass of crunchify : class java . lang . Object
2. Superclass of crunchifyDouble : class java . lang . Number
 
How to check if class is Primitive Type of not ? ==================== Example 5
1. Is 'int' a Prmitive Type : true
2. Is 'String' a Prmitive Type : false
3. Is 'double' a Prmitive Type : true
 
How to create object using Constructor object ? ==================== Example 6
1. String . class = Hello World !
2. StringBuilder . class = Hello Universe !
 
How to get constructors of a class object ==================== Example 7
- Constructor = crunchify . com . tutorials . CrunchifyPOJO
 
How to get field of a class object ==================== Example 8
- name
- email
 
How to invoke a method using Method class ==================== Example 9
- Hey This is Crunchify ' s Refection API tutorials . More than 400 Tutorials on Crunchify . com
 
get all Declared Class Fields ==================== Example 10
field name : name , type : class java . lang . String
field name : webAddress , type : class java . lang . String
field name : email , type : class java . lang . String
field name : zip , type : int

Contoh lengkapnya dapat dijelaskan sendiri karena saya mencoba yang terbaik untuk memasukkan sebanyak mungkin sistem ke dalam program itu sendiri.

Cobalah dan beri tahu saya jika Anda memiliki pertanyaan. Selamat mengkode.