Merge branch 'feature/design-pattern-v2.6.0-ft-211014-implement-proxy-pattern' into develop

Author: ThanhPhiNgo

README.md

@@ -56,8 +56,7 @@ Reference: https://gpcoder.com/4554-huong-dan-java-design-pattern-composite/
 Reference: https://gpcoder.com/4574-huong-dan-java-design-pattern-decorator/
 
 > :warning: Note: <br/>
-> In this code, we can only add new features to the object. We cannot remove the previous features of this object.<br/>
-> _Example_: Manager becomes TeamLeader, TeamLeader still doTask of Manager. **This is Problem**
+> In this code, we can only add new features to the object. We cannot remove the previous features of this object.<br/> > _Example_: Manager becomes TeamLeader, TeamLeader still doTask of Manager. **This is Problem**
 
 ### Facade
 
@@ -66,4 +65,11 @@ Reference: https://gpcoder.com/4604-huong-dan-java-design-pattern-facade/
 ### Flyweight
 
 Reference: https://gpcoder.com/4626-huong-dan-java-design-pattern-flyweight/
-Review: Good for create character in game
+
+> Review: Good for create character in game
+
+### Proxy
+
+https://gpcoder.com/4644-huong-dan-java-design-pattern-proxy/
+
+> Review: Useful for lazy loading

design-pattern/pom.xml

@@ -6,7 +6,7 @@
 
     <groupId>com.phint2</groupId>
     <artifactId>design-pattern</artifactId>
-    <version>2.5.0</version>
+    <version>2.6.0</version>
 
     <properties>
         <maven.compiler.source>8</maven.compiler.source>

design-pattern/src/main/java/com/phint2/pattern/structural/proxy/protection/Client.java

@@ -0,0 +1,14 @@
+package com.phint2.pattern.structural.proxy.protection;
+
+public class Client {
+
+	public static void main(String[] args) {
+		UserService admin = new UserServiceProxy("phint", "admin");
+		admin.load();
+		admin.insert();
+
+		UserService customer = new UserServiceProxy("customer", "guest");
+		customer.load();
+		customer.insert();
+	}
+}

design-pattern/src/main/java/com/phint2/pattern/structural/proxy/protection/UserService.java

@@ -0,0 +1,7 @@
+package com.phint2.pattern.structural.proxy.protection;
+
+public interface UserService {
+
+	void load();
+	void insert();
+}

design-pattern/src/main/java/com/phint2/pattern/structural/proxy/protection/UserServiceImpl.java

@@ -0,0 +1,20 @@
+package com.phint2.pattern.structural.proxy.protection;
+
+public class UserServiceImpl implements UserService {
+
+	private String name;
+
+	public UserServiceImpl(String name) {
+		this.name = name;
+	}
+
+	@Override
+	public void load() {
+		System.out.println(name + " loaded");
+	}
+
+	@Override
+	public void insert() {
+		System.out.println(name + " inserted");
+	}
+}

design-pattern/src/main/java/com/phint2/pattern/structural/proxy/protection/UserServiceProxy.java

@@ -0,0 +1,31 @@
+package com.phint2.pattern.structural.proxy.protection;
+
+public class UserServiceProxy implements UserService {
+
+	private static final String ADMIN = "admin";
+	private String role;
+	private UserService userService;
+
+	public UserServiceProxy(String name, String role) {
+		this.role = role;
+		this.userService = new UserServiceImpl(name);
+	}
+
+	@Override
+	public void load() {
+		userService.load();
+	}
+
+	@Override
+	public void insert() {
+		if (isAdmin()) {
+			userService.insert();
+		} else {
+			throw new IllegalAccessError("Access denied");
+		}
+	}
+
+	private boolean isAdmin() {
+		return ADMIN.equalsIgnoreCase(this.role);
+	}
+}

design-pattern/src/main/java/com/phint2/pattern/structural/proxy/virtual/Client.java

@@ -0,0 +1,17 @@
+package com.phint2.pattern.structural.proxy.virtual;
+
+public class Client {
+
+	public static void main(String[] args) {
+		System.out.println("Init proxy image: ");
+		ProxyImage proxyImage = new ProxyImage("abc.com");
+
+		System.out.println("---");
+		System.out.println("Call real service 1st: ");
+		proxyImage.showImage();
+
+		System.out.println("---");
+		System.out.println("Call real service 2nd: ");
+		proxyImage.showImage();
+	}
+}

design-pattern/src/main/java/com/phint2/pattern/structural/proxy/virtual/Image.java

@@ -0,0 +1,6 @@
+package com.phint2.pattern.structural.proxy.virtual;
+
+public interface Image {
+
+	void showImage();
+}

design-pattern/src/main/java/com/phint2/pattern/structural/proxy/virtual/ProxyImage.java

@@ -0,0 +1,22 @@
+package com.phint2.pattern.structural.proxy.virtual;
+
+public class ProxyImage implements Image {
+
+	private RealImage realImage;
+	private String url;
+
+	public ProxyImage(String url) {
+		this.url = url;
+		System.out.println("Image unloaded: " + this.url);
+	}
+
+	@Override
+	public void showImage() {
+		if (null == realImage) {
+			realImage = new RealImage(this.url);
+		} else {
+			System.out.println("Image already existed: " + this.url);
+		}
+		realImage.showImage();
+	}
+}

design-pattern/src/main/java/com/phint2/pattern/structural/proxy/virtual/RealImage.java

@@ -0,0 +1,16 @@
+package com.phint2.pattern.structural.proxy.virtual;
+
+public class RealImage implements Image {
+
+	private String url;
+
+	public RealImage(String url) {
+		this.url = url;
+		System.out.println("Image loaded: " + this.url);
+	}
+
+	@Override
+	public void showImage() {
+		System.out.println("Image showed: " + this.url);
+	}
+}