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implemented Dependency Injection using Injector, Inject and Component annotations #702

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5 changes: 3 additions & 2 deletions src/main/java/mate.academy/Main.java
Original file line number Diff line number Diff line change
Expand Up @@ -4,13 +4,14 @@
import mate.academy.lib.Injector;
import mate.academy.model.Product;
import mate.academy.service.ProductService;
import mate.academy.service.impl.ProductServiceImpl;

public class Main {

public static void main(String[] args) {
// Please test your Injector here. Feel free to push this class as a part of your solution
Injector injector = Injector.getInjector();
ProductService productService = null;
ProductService productService =
(ProductService) injector.getInstance(ProductServiceImpl.class);
List<Product> products = productService.getAllFromFile("products.txt");
products.forEach(System.out::println);
}
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8 changes: 7 additions & 1 deletion src/main/java/mate.academy/lib/Component.java
Original file line number Diff line number Diff line change
@@ -1,5 +1,11 @@
package mate.academy.lib;

public @interface Component {
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
public @interface Component {
}
7 changes: 7 additions & 0 deletions src/main/java/mate.academy/lib/Inject.java
Original file line number Diff line number Diff line change
@@ -1,5 +1,12 @@
package mate.academy.lib;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.FIELD)
public @interface Inject {

}
72 changes: 70 additions & 2 deletions src/main/java/mate.academy/lib/Injector.java
Original file line number Diff line number Diff line change
@@ -1,13 +1,81 @@
package mate.academy.lib;

import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.util.HashMap;
import java.util.Map;
import mate.academy.service.FileReaderService;
import mate.academy.service.ProductParser;
import mate.academy.service.ProductService;
import mate.academy.service.impl.FileReaderServiceImpl;
import mate.academy.service.impl.ProductParserImpl;
import mate.academy.service.impl.ProductServiceImpl;

public class Injector {
private static final Injector injector = new Injector();
private static final Map<Class<?>, Object> instances = new HashMap<>();
private static final Map<Class<?>, Class<?>> implementations = new HashMap<>(Map.of(
FileReaderService.class, FileReaderServiceImpl.class,
ProductParser.class, ProductParserImpl.class,
ProductService.class, ProductServiceImpl.class));

public static Injector getInjector() {
return injector;
}

public Object getInstance(Class<?> interfaceClazz) {
return null;
public Object getInstance(Class<?> type) {
Field[] fields = type.getDeclaredFields();
Class<?> classType = findImplementation(type);
Object implementationInstance = null;
checkIfComponent(classType);
for (Field field : fields) {
if (field.isAnnotationPresent(Inject.class)) {
Object fieldInstance = getInstance(field.getType());
implementationInstance = createNewInstance(classType);
field.setAccessible(true);
try {
field.set(implementationInstance, fieldInstance);
} catch (IllegalAccessException e) {
throw new RuntimeException("Injection failed, "
+ "can't initialize field value:" + field.getName()
+ " in " + type.getName());
}
}
}
if (implementationInstance == null) {
implementationInstance = createNewInstance(classType);
}
return implementationInstance;
}

private void checkIfComponent(Class<?> classType) {
if (!classType.isAnnotationPresent(Component.class)) {
throw new RuntimeException("Injection failed, "
+ "missing @Component annotation on the class " + classType.getName());
}
}

private Object createNewInstance(Class<?> classType) {
if (instances.containsKey(classType)) {
return instances.get(classType);
}
try {
Constructor<?> constructor = classType.getConstructor();
Object instance = constructor.newInstance();
instances.put(classType, instance);
return instance;
} catch (NoSuchMethodException | InstantiationException
| IllegalAccessException | InvocationTargetException e) {
throw new RuntimeException("Injection failed, "
+ "cannot create an instance of " + classType.getName(), e);
}
}

private Class<?> findImplementation(Class<?> classInterface) {
if (!classInterface.isInterface()) {
return classInterface;
}
return implementations.get(classInterface);
}
}
Original file line number Diff line number Diff line change
Expand Up @@ -4,8 +4,10 @@
import java.io.IOException;
import java.nio.file.Files;
import java.util.List;
import mate.academy.lib.Component;
import mate.academy.service.FileReaderService;

@Component
public class FileReaderServiceImpl implements FileReaderService {
@Override
public List<String> readFile(String fileName) {
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Original file line number Diff line number Diff line change
@@ -1,9 +1,11 @@
package mate.academy.service.impl;

import java.math.BigDecimal;
import mate.academy.lib.Component;
import mate.academy.model.Product;
import mate.academy.service.ProductParser;

@Component
public class ProductParserImpl implements ProductParser {
public static final int ID_POSITION = 0;
public static final int NAME_POSITION = 1;
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Original file line number Diff line number Diff line change
Expand Up @@ -2,13 +2,18 @@

import java.util.List;
import java.util.stream.Collectors;
import mate.academy.lib.Component;
import mate.academy.lib.Inject;
import mate.academy.model.Product;
import mate.academy.service.FileReaderService;
import mate.academy.service.ProductParser;
import mate.academy.service.ProductService;

@Component
public class ProductServiceImpl implements ProductService {
@Inject
private ProductParser productParser;
@Inject
private FileReaderService fileReaderService;

@Override
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