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BAEL-4587: Update Guide to Java Reflection (#9997)

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* BAEL-4587: Migrate Guide to Java Reflection to core-java-11-2

* BAEL-4587: Replace deprecated isAccessible method with canAccess
This commit is contained in:
kwoyke
2020-09-12 19:08:22 +02:00
committed by GitHub
parent faa858e766
commit 972ff96699
15 changed files with 46 additions and 54 deletions
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core-java-modules/core-java-reflection/README.MD
-1
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@@ -3,7 +3,6 @@
- [Void Type in Java](https://www.baeldung.com/java-void-type)
- [Retrieve Fields from a Java Class Using Reflection](https://www.baeldung.com/java-reflection-class-fields)
- [Method Parameter Reflection in Java](http://www.baeldung.com/java-parameter-reflection)
- [Guide to Java Reflection](http://www.baeldung.com/java-reflection)
- [Call Methods at Runtime Using Java Reflection](http://www.baeldung.com/java-method-reflection)
- [Changing Annotation Parameters At Runtime](http://www.baeldung.com/java-reflection-change-annotation-params)
- [Dynamic Proxies in Java](http://www.baeldung.com/java-dynamic-proxies)
core-java-modules/core-java-reflection/src/main/java/com/baeldung/reflection/java/reflection/Animal.java
-23
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@@ -1,23 +0,0 @@
package com.baeldung.java.reflection;
public abstract class Animal implements Eating {
public static final String CATEGORY = "domestic";
private String name;
public Animal(String name) {
this.name = name;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
protected abstract String getSound();
}
core-java-modules/core-java-reflection/src/main/java/com/baeldung/reflection/java/reflection/Bird.java
-36
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@@ -1,36 +0,0 @@
package com.baeldung.java.reflection;
public class Bird extends Animal {
private boolean walks;
public Bird() {
super("bird");
}
public Bird(String name, boolean walks) {
super(name);
setWalks(walks);
}
public Bird(String name) {
super(name);
}
@Override
public String eats() {
return "grains";
}
@Override
protected String getSound() {
return "chaps";
}
public boolean walks() {
return walks;
}
public void setWalks(boolean walks) {
this.walks = walks;
}
}
core-java-modules/core-java-reflection/src/main/java/com/baeldung/reflection/java/reflection/DynamicGreeter.java
-23
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@@ -1,23 +0,0 @@
package com.baeldung.java.reflection;
import java.lang.annotation.Annotation;
public class DynamicGreeter implements Greeter {
private String greet;
public DynamicGreeter(String greet) {
this.greet = greet;
}
@Override
public Class<? extends Annotation> annotationType() {
return DynamicGreeter.class;
}
@Override
public String greet() {
return greet;
}
}
core-java-modules/core-java-reflection/src/main/java/com/baeldung/reflection/java/reflection/Eating.java
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@@ -1,5 +0,0 @@
package com.baeldung.java.reflection;
public interface Eating {
String eats();
}
core-java-modules/core-java-reflection/src/main/java/com/baeldung/reflection/java/reflection/Goat.java
-24
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@@ -1,24 +0,0 @@
package com.baeldung.java.reflection;
public class Goat extends Animal implements Locomotion {
public Goat(String name) {
super(name);
}
@Override
protected String getSound() {
return "bleat";
}
@Override
public String getLocomotion() {
return "walks";
}
@Override
public String eats() {
return "grass";
}
}
core-java-modules/core-java-reflection/src/main/java/com/baeldung/reflection/java/reflection/Greeter.java
-10
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@@ -1,10 +0,0 @@
package com.baeldung.java.reflection;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
@Retention(RetentionPolicy.RUNTIME)
public @interface Greeter {
public String greet() default "";
}
core-java-modules/core-java-reflection/src/main/java/com/baeldung/reflection/java/reflection/GreetingAnnotation.java
-58
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@@ -1,58 +0,0 @@
package com.baeldung.java.reflection;
import java.lang.annotation.Annotation;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.util.Map;
public class GreetingAnnotation {
private static final String ANNOTATION_METHOD = "annotationData";
private static final String ANNOTATION_FIELDS = "declaredAnnotations";
private static final String ANNOTATIONS = "annotations";
public static void main(String ...args) {
Greeter greetings = Greetings.class.getAnnotation(Greeter.class);
System.err.println("Hello there, " + greetings.greet() + " !!");
Greeter targetValue = new DynamicGreeter("Good evening");
//alterAnnotationValueJDK8(Greetings.class, Greeter.class, targetValue);
alterAnnotationValueJDK7(Greetings.class, Greeter.class, targetValue);
greetings = Greetings.class.getAnnotation(Greeter.class);
System.err.println("Hello there, " + greetings.greet() + " !!");
}
@SuppressWarnings("unchecked")
public static void alterAnnotationValueJDK8(Class<?> targetClass, Class<? extends Annotation> targetAnnotation, Annotation targetValue) {
try {
Method method = Class.class.getDeclaredMethod(ANNOTATION_METHOD, null);
method.setAccessible(true);
Object annotationData = method.invoke(targetClass);
Field annotations = annotationData.getClass().getDeclaredField(ANNOTATIONS);
annotations.setAccessible(true);
Map<Class<? extends Annotation>, Annotation> map = (Map<Class<? extends Annotation>, Annotation>) annotations.get(annotationData);
map.put(targetAnnotation, targetValue);
} catch (Exception e) {
e.printStackTrace();
}
}
@SuppressWarnings("unchecked")
public static void alterAnnotationValueJDK7(Class<?> targetClass, Class<? extends Annotation> targetAnnotation, Annotation targetValue) {
try {
Field annotations = Class.class.getDeclaredField(ANNOTATIONS);
annotations.setAccessible(true);
Map<Class<? extends Annotation>, Annotation> map = (Map<Class<? extends Annotation>, Annotation>) annotations.get(targetClass);
System.out.println(map);
map.put(targetAnnotation, targetValue);
System.out.println(map);
} catch (Exception e) {
e.printStackTrace();
}
}
}
core-java-modules/core-java-reflection/src/main/java/com/baeldung/reflection/java/reflection/Greetings.java
-6
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@@ -1,6 +0,0 @@
package com.baeldung.java.reflection;
@Greeter(greet="Good morning")
public class Greetings {
}
core-java-modules/core-java-reflection/src/main/java/com/baeldung/reflection/java/reflection/Locomotion.java
-5
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@@ -1,5 +0,0 @@
package com.baeldung.java.reflection;
public interface Locomotion {
String getLocomotion();
}
core-java-modules/core-java-reflection/src/main/java/com/baeldung/reflection/java/reflection/Operations.java
-21
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@@ -1,21 +0,0 @@
package com.baeldung.java.reflection;
public class Operations {
public double publicSum(int a, double b) {
return a + b;
}
public static double publicStaticMultiply(float a, long b) {
return a * b;
}
private boolean privateAnd(boolean a, boolean b) {
return a && b;
}
protected int protectedMax(int a, int b) {
return a > b ? a : b;
}
}
core-java-modules/core-java-reflection/src/main/java/com/baeldung/reflection/java/reflection/Person.java
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@@ -1,6 +0,0 @@
package com.baeldung.java.reflection;
public class Person {
private String name;
private int age;
}
core-java-modules/core-java-reflection/src/test/java/com/baeldung/reflection/java/reflection/OperationsUnitTest.java
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@@ -1,57 +0,0 @@
package com.baeldung.java.reflection;
import static org.hamcrest.CoreMatchers.equalTo;
import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertThat;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import org.junit.Test;
public class OperationsUnitTest {
public OperationsUnitTest() {
}
@Test(expected = IllegalAccessException.class)
public void givenObject_whenInvokePrivateMethod_thenFail() throws NoSuchMethodException, IllegalAccessException, IllegalArgumentException, InvocationTargetException {
Method andPrivateMethod = Operations.class.getDeclaredMethod("privateAnd", boolean.class, boolean.class);
Operations operationsInstance = new Operations();
Boolean result = (Boolean) andPrivateMethod.invoke(operationsInstance, true, false);
assertFalse(result);
}
@Test
public void givenObject_whenInvokePrivateMethod_thenCorrect() throws Exception {
Method andPrivatedMethod = Operations.class.getDeclaredMethod("privateAnd", boolean.class, boolean.class);
andPrivatedMethod.setAccessible(true);
Operations operationsInstance = new Operations();
Boolean result = (Boolean) andPrivatedMethod.invoke(operationsInstance, true, false);
assertFalse(result);
}
@Test
public void givenObject_whenInvokePublicMethod_thenCorrect() throws Exception {
Method sumInstanceMethod = Operations.class.getMethod("publicSum", int.class, double.class);
Operations operationsInstance = new Operations();
Double result = (Double) sumInstanceMethod.invoke(operationsInstance, 1, 3);
assertThat(result, equalTo(4.0));
}
@Test
public void givenObject_whenInvokeStaticMethod_thenCorrect() throws Exception {
Method multiplyStaticMethod = Operations.class.getDeclaredMethod("publicStaticMultiply", float.class, long.class);
Double result = (Double) multiplyStaticMethod.invoke(null, 3.5f, 2);
assertThat(result, equalTo(7.0));
}
}
core-java-modules/core-java-reflection/src/test/java/com/baeldung/reflection/java/reflection/ReflectionUnitTest.java
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