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Merge pull request #662 from egimaben/master 

Java reflection tutorial project
This commit is contained in:
Alex Theedom 2016-09-03 19:13:26 +01:00 committed by GitHub
parent 335770683c cb2c9d882c
commit d4706b98ef
9 changed files with 448 additions and 0 deletions
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3
pom.xml
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@ -117,6 +117,9 @@
<module>xstream</module>
<module>dozer</module>
<module>orika</module>
<module>reflection</module>
<module>dozer</module>
<module>orika</module>
</modules>
</project>

30
reflection/pom.xml Normal file
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@ -0,0 +1,30 @@
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.baeldung</groupId>
<artifactId>reflection</artifactId>
<version>1.0</version>
<name>reflection</name>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.3</version>
<configuration>
<source>7</source>
<target>7</target>
</configuration>
</plugin>
</plugins>
</build>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.3</version>
<scope>test</scope>
</dependency>
</dependencies>
</project>

26
reflection/src/main/java/com/baeldung/reflection/Animal.java Normal file
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package com.baeldung.reflection;
public abstract class Animal implements Eating{
public static final String CATEGORY = "domestic";
private String name;
public Animal(String name) {
super();
this.name = name;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String makeSound() {
return getSound();
}
protected abstract String getSound();
}

33
reflection/src/main/java/com/baeldung/reflection/Bird.java Normal file
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package com.baeldung.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;
}
}

5
reflection/src/main/java/com/baeldung/reflection/Eating.java Normal file
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@ -0,0 +1,5 @@
package com.baeldung.reflection;
public interface Eating {
public String eats();
}

24
reflection/src/main/java/com/baeldung/reflection/Goat.java Normal file
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@ -0,0 +1,24 @@
package com.baeldung.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";
}
}

5
reflection/src/main/java/com/baeldung/reflection/Locomotion.java Normal file
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@ -0,0 +1,5 @@
package com.baeldung.reflection;
public interface Locomotion {
public String getLocomotion();
}

6
reflection/src/main/java/com/baeldung/reflection/Person.java Normal file
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@ -0,0 +1,6 @@
package com.baeldung.reflection;
public class Person {
private String name;
private int age;
}

316
reflection/src/test/java/com/baeldung/reflection/ReflectionTest.java Normal file
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package com.baeldung.reflection;
import static org.junit.Assert.*;
import java.lang.reflect.*;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import org.junit.Test;
public class ReflectionTest {
@Test
public void givenObject_whenGetsFieldNamesAtRuntime_thenCorrect() {
Object person = new Person();
Field[] fields = person.getClass().getDeclaredFields();
List<String> expectedFieldNames = Arrays.asList(new String[] { "name",
"age" });
List<String> actualFieldNames = new ArrayList<>();
for (Field field : fields)
actualFieldNames.add(field.getName());
assertTrue(expectedFieldNames.containsAll(actualFieldNames));
}
@Test
public void givenObject_whenGetsClassName_thenCorrect() {
Object goat = new Goat("goat");
Class<?> clazz = goat.getClass();
assertEquals("Goat", clazz.getSimpleName());
assertEquals("com.baeldung.reflection.Goat", clazz.getName());
assertEquals("com.baeldung.reflection.Goat", clazz.getCanonicalName());
}
@Test
public void givenClassName_whenCreatesObject_thenCorrect()
throws ClassNotFoundException {
Class<?> clazz = Class.forName("com.baeldung.reflection.Goat");
assertEquals("Goat", clazz.getSimpleName());
assertEquals("com.baeldung.reflection.Goat", clazz.getName());
assertEquals("com.baeldung.reflection.Goat", clazz.getCanonicalName());
}
@Test
public void givenClass_whenRecognisesModifiers_thenCorrect()
throws ClassNotFoundException {
Class<?> goatClass = Class.forName("com.baeldung.reflection.Goat");
Class<?> animalClass = Class.forName("com.baeldung.reflection.Animal");
int goatMods = goatClass.getModifiers();
int animalMods = animalClass.getModifiers();
assertTrue(Modifier.isPublic(goatMods));
assertTrue(Modifier.isAbstract(animalMods));
assertTrue(Modifier.isPublic(animalMods));
}
@Test
public void givenClass_whenGetsPackageInfo_thenCorrect() {
Goat goat = new Goat("goat");
Class<?> goatClass = goat.getClass();
Package pkg = goatClass.getPackage();
assertEquals("com.baeldung.reflection", pkg.getName());
}
@Test
public void givenClass_whenGetsSuperClass_thenCorrect() {
Goat goat = new Goat("goat");
String str = "any string";
Class<?> goatClass = goat.getClass();
Class<?> goatSuperClass = goatClass.getSuperclass();
assertEquals("Animal", goatSuperClass.getSimpleName());
assertEquals("Object", str.getClass().getSuperclass().getSimpleName());
}
@Test
public void givenClass_whenGetsImplementedInterfaces_thenCorrect()
throws ClassNotFoundException {
Class<?> goatClass = Class.forName("com.baeldung.reflection.Goat");
Class<?> animalClass = Class.forName("com.baeldung.reflection.Animal");
Class<?>[] goatInterfaces = goatClass.getInterfaces();
Class<?>[] animalInterfaces = animalClass.getInterfaces();
assertEquals(1, goatInterfaces.length);
assertEquals(1, animalInterfaces.length);
assertEquals("Locomotion", goatInterfaces[0].getSimpleName());
assertEquals("Eating", animalInterfaces[0].getSimpleName());
}
@Test
public void givenClass_whenGetsConstructor_thenCorrect()
throws ClassNotFoundException {
Class<?> goatClass = Class.forName("com.baeldung.reflection.Goat");
Constructor<?>[] constructors = goatClass.getConstructors();
assertEquals(1, constructors.length);
assertEquals("com.baeldung.reflection.Goat", constructors[0].getName());
}
@Test
public void givenClass_whenGetsFields_thenCorrect()
throws ClassNotFoundException {
Class<?> animalClass = Class.forName("com.baeldung.reflection.Animal");
Field[] fields = animalClass.getDeclaredFields();
List<String> expectedFields = Arrays.asList(new String[] { "name",
"CATEGORY" });
List<String> actualFields = new ArrayList<>();
for (Field field : fields)
actualFields.add(field.getName());
assertEquals(2, actualFields.size());
assertTrue(actualFields.containsAll(expectedFields));
}
@Test
public void givenClass_whenGetsMethods_thenCorrect()
throws ClassNotFoundException {
Class<?> animalClass = Class.forName("com.baeldung.reflection.Animal");
Method[] methods = animalClass.getDeclaredMethods();
List<String> expectedMethods = Arrays.asList(new String[] { "getName",
"setName", "getSound", "makeSound" });
List<String> actualMethods = new ArrayList<>();
for (Method method : methods)
actualMethods.add(method.getName());
assertEquals(4, actualMethods.size());
assertTrue(actualMethods.containsAll(expectedMethods));
}
@Test
public void givenClass_whenGetsAllConstructors_thenCorrect()
throws ClassNotFoundException {
Class<?> birdClass = Class.forName("com.baeldung.reflection.Bird");
Constructor<?>[] constructors = birdClass.getConstructors();
assertEquals(3, constructors.length);
}
@Test
public void givenClass_whenGetsEachConstructorByParamTypes_thenCorrect()
throws ClassNotFoundException, NoSuchMethodException,
SecurityException {
Class<?> birdClass = Class.forName("com.baeldung.reflection.Bird");
Constructor<?> cons1 = birdClass.getConstructor();
Constructor<?> cons2 = birdClass.getConstructor(String.class);
Constructor<?> cons3 = birdClass.getConstructor(String.class,
boolean.class);
}
@Test
public void givenClass_whenInstantiatesObjectsAtRuntime_thenCorrect()
throws ClassNotFoundException, NoSuchMethodException,
SecurityException, InstantiationException, IllegalAccessException,
IllegalArgumentException, InvocationTargetException {
Class<?> birdClass = Class.forName("com.baeldung.reflection.Bird");
Constructor<?> cons1 = birdClass.getConstructor();
Constructor<?> cons2 = birdClass.getConstructor(String.class);
Constructor<?> cons3 = birdClass.getConstructor(String.class,
boolean.class);
Bird bird1 = (Bird) cons1.newInstance();
Bird bird2 = (Bird) cons2.newInstance("Weaver bird");
Bird bird3 = (Bird) cons3.newInstance("dove", true);
assertEquals("bird", bird1.getName());
assertEquals("Weaver bird", bird2.getName());
assertEquals("dove", bird3.getName());
assertFalse(bird1.walks());
assertTrue(bird3.walks());
}
@Test
public void givenClass_whenGetsPublicFields_thenCorrect()
throws ClassNotFoundException {
Class<?> birdClass = Class.forName("com.baeldung.reflection.Bird");
Field[] fields = birdClass.getFields();
assertEquals(1, fields.length);
assertEquals("CATEGORY", fields[0].getName());
}
@Test
public void givenClass_whenGetsPublicFieldByName_thenCorrect()
throws ClassNotFoundException, NoSuchFieldException,
SecurityException {
Class<?> birdClass = Class.forName("com.baeldung.reflection.Bird");
Field field = birdClass.getField("CATEGORY");
assertEquals("CATEGORY", field.getName());
}
@Test
public void givenClass_whenGetsDeclaredFields_thenCorrect()
throws ClassNotFoundException {
Class<?> birdClass = Class.forName("com.baeldung.reflection.Bird");
Field[] fields = birdClass.getDeclaredFields();
assertEquals(1, fields.length);
assertEquals("walks", fields[0].getName());
}
@Test
public void givenClass_whenGetsFieldsByName_thenCorrect()
throws ClassNotFoundException, NoSuchFieldException,
SecurityException {
Class<?> birdClass = Class.forName("com.baeldung.reflection.Bird");
Field field = birdClass.getDeclaredField("walks");
assertEquals("walks", field.getName());
}
@Test
public void givenClassField_whenGetsType_thenCorrect()
throws ClassNotFoundException, NoSuchFieldException,
SecurityException {
Field field = Class.forName("com.baeldung.reflection.Bird")
.getDeclaredField("walks");
Class<?> fieldClass = field.getType();
assertEquals("boolean", fieldClass.getSimpleName());
}
@Test
public void givenClassField_whenSetsAndGetsValue_thenCorrect()
throws ClassNotFoundException, NoSuchFieldException,
SecurityException, InstantiationException, IllegalAccessException {
Class<?> birdClass = Class.forName("com.baeldung.reflection.Bird");
Bird bird = (Bird) birdClass.newInstance();
Field field = birdClass.getDeclaredField("walks");
field.setAccessible(true);
assertFalse(field.getBoolean(bird));
assertFalse(bird.walks());
field.set(bird, true);
assertTrue(field.getBoolean(bird));
assertTrue(bird.walks());
}
@Test
public void givenClassField_whenGetsAndSetsWithNull_thenCorrect()
throws ClassNotFoundException, InstantiationException,
IllegalAccessException, NoSuchFieldException, SecurityException {
Class<?> birdClass = Class.forName("com.baeldung.reflection.Bird");
Field field = birdClass.getField("CATEGORY");
field.setAccessible(true);
assertEquals("domestic", field.get(null));
}
@Test
public void givenClass_whenGetsAllPublicMethods_thenCorrect()
throws ClassNotFoundException {
Class<?> birdClass = Class.forName("com.baeldung.reflection.Bird");
Method[] methods = birdClass.getMethods();
List<String> methodNames = new ArrayList<>();
for (Method method : methods)
methodNames.add(method.getName());
assertTrue(methodNames.containsAll(Arrays
.asList(new String[] { "equals", "notifyAll", "hashCode",
"walks", "eats", "toString" })));
}
@Test
public void givenClass_whenGetsOnlyDeclaredMethods_thenCorrect()
throws ClassNotFoundException {
Class<?> birdClass = Class.forName("com.baeldung.reflection.Bird");
Method[] methods = birdClass.getDeclaredMethods();
List<String> expectedMethodNames = Arrays.asList(new String[] {
"setWalks", "walks", "getSound", "eats" });
List<String> actualMethodNames = new ArrayList<>();
for (Method method : methods)
actualMethodNames.add(method.getName());
assertEquals(expectedMethodNames.size(), actualMethodNames.size());
assertTrue(expectedMethodNames.containsAll(actualMethodNames));
assertTrue(actualMethodNames.containsAll(expectedMethodNames));
}
@Test
public void givenMethodName_whenGetsMethod_thenCorrect()
throws ClassNotFoundException, NoSuchMethodException,
SecurityException {
Class<?> birdClass = Class.forName("com.baeldung.reflection.Bird");
Method walksMethod = birdClass.getDeclaredMethod("walks");
Method setWalksMethod = birdClass.getDeclaredMethod("setWalks",
boolean.class);
assertFalse(walksMethod.isAccessible());
assertFalse(setWalksMethod.isAccessible());
walksMethod.setAccessible(true);
setWalksMethod.setAccessible(true);
assertTrue(walksMethod.isAccessible());
assertTrue(setWalksMethod.isAccessible());
}
@Test
public void givenMethod_whenInvokes_thenCorrect()
throws ClassNotFoundException, NoSuchMethodException,
SecurityException, IllegalAccessException,
IllegalArgumentException, InvocationTargetException,
InstantiationException {
Class<?> birdClass = Class.forName("com.baeldung.reflection.Bird");
Bird bird = (Bird) birdClass.newInstance();
Method setWalksMethod = birdClass.getDeclaredMethod("setWalks",
boolean.class);
Method walksMethod = birdClass.getDeclaredMethod("walks");
boolean walks = (boolean) walksMethod.invoke(bird);
assertFalse(walks);
assertFalse(bird.walks());
setWalksMethod.invoke(bird, true);
boolean walks2 = (boolean) walksMethod.invoke(bird);
assertTrue(walks2);
assertTrue(bird.walks());
}
}