study java io

core-banking/src/com/example/banking/application/ReadCustomerFromFile.java

@@ -0,0 +1,28 @@
+package com.example.banking.application;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileNotFoundException;
+import java.io.FileOutputStream;
+import java.io.ObjectInputStream;
+import java.io.ObjectOutputStream;
+
+import com.example.banking.domain.Account;
+import com.example.banking.domain.CheckingAccount;
+import com.example.banking.domain.Customer;
+
+public class ReadCustomerFromFile {
+
+	public static void main(String[] args) throws Exception {
+		var file = new File("c:/tmp", "jack.dat");
+		// try-with-resources, Java 7+
+		try (var fis = new FileInputStream(file); 
+			 var ois = new ObjectInputStream(fis);) {
+			Customer jack = (Customer) ois.readObject();
+			System.err.println(jack);
+			var totalBalance = jack.getTotalBalance();
+			System.err.println("Total balance: "+totalBalance);
+		}
+	}
+
+}

core-banking/src/com/example/banking/application/WriteCustomerToFile.java

@@ -0,0 +1,28 @@
+package com.example.banking.application;
+
+import java.io.File;
+import java.io.FileNotFoundException;
+import java.io.FileOutputStream;
+import java.io.ObjectOutputStream;
+
+import com.example.banking.domain.Account;
+import com.example.banking.domain.CheckingAccount;
+import com.example.banking.domain.Customer;
+
+public class WriteCustomerToFile {
+
+	public static void main(String[] args) throws Exception {
+		var jack = new Customer("1111111110", "Jack Bauer");
+		jack.addAccount(new Account("tr1", 100_000));
+		jack.addAccount(new CheckingAccount("tr2", 200_000, 5_000));
+		jack.addAccount(new Account("tr3", 300_000));
+		var file = new File("c:/tmp", "jack.dat");
+		// try-with-resources, Java 7+
+		try (var fos = new FileOutputStream(file); 
+			 var oos = new ObjectOutputStream(fos);) {
+			oos.writeObject(jack);
+		}
+        System.err.println("Object is written to the file.");
+	}
+
+}

core-banking/src/com/example/banking/domain/Account.java

@@ -1,7 +1,13 @@
 package com.example.banking.domain;
 
+import java.io.Serializable;
+
 // Encapsulation: fields + methods
-public class Account extends Object {
+public class Account extends Object implements Serializable {
+	/**
+	 * 
+	 */
+	private static final long serialVersionUID = 1L;
 	// private : information hiding principle
 	private final String iban; // field/state/attribute
 	double balance; // < 0.0 -> illegal state

core-banking/src/com/example/banking/domain/Customer.java

@@ -1,11 +1,16 @@
 package com.example.banking.domain;
 
+import java.io.Serializable;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Optional;
 
 // DDD: Entity Class -> Persistent, Identity
-public class Customer {
+public class Customer implements Serializable {
+	/**
+	 * 
+	 */
+	private static final long serialVersionUID = 1L;
 	private final String identity; // does allow to change
 	private String fullName;
 	private List<Account> accounts;
@@ -67,4 +72,11 @@ public double getTotalBalance8() {
 	public int getNumberOfAccounts() {
 		return accounts.size();
 	}
+
+	@Override
+	public String toString() {
+		return "Customer [identity=" + identity + ", fullName=" + fullName + ", accounts=" + accounts + "]";
+	}
+
+
 }