Enhance sample to show method authorization.

samples/tutorial/src/main/java/bigbank/BankServiceImpl.java

@@ -0,0 +1,35 @@
+package bigbank;
+
+import org.springframework.util.Assert;
+
+public class BankServiceImpl implements BankService {
+	private BankDao bankDao;
+	
+	public BankServiceImpl(BankDao bankDao) {
+		Assert.notNull(bankDao);
+		this.bankDao = bankDao;
+	}
+
+	public Account[] findAccounts() {
+		return this.bankDao.findAccounts();
+	}
+
+	public Account post(Account account, double amount) {
+		Assert.notNull(account);
+		Assert.notNull(account.getId());
+		
+		// We read account bank from DAO so it reflects the latest balance
+		Account a = bankDao.readAccount(account.getId());
+		if (account == null) {
+			throw new IllegalArgumentException("Couldn't find requested account");
+		}
+		
+		a.setBalance(a.getBalance() + amount);
+		bankDao.createOrUpdateAccount(a);
+		return a;
+	}
+
+	public Account readAccount(Long id) {
+		return bankDao.readAccount(id);
+	}
+}