www.pudn.com > EJB3eCode.zip > AccountBean.java
package examples.bmp; import java.sql.*; import javax.naming.*; import javax.ejb.*; import java.util.*; /** * Demonstration Bean-Managed Persistent Entity Bean. * This Entity Bean represents a Bank Account. */ public class AccountBean implements EntityBean { protected EntityContext ctx; // // Bean-managed state fields // private String accountID; // PK private String ownerName; private double balance; public AccountBean() { System.out.println("New Bank Account Entity Bean Java Object created by EJB Container."); } // // Business Logic Methods // /** * Deposits amt into account. */ public void deposit(double amt) throws AccountException { System.out.println("deposit(" + amt + ") called."); balance += amt; } /** * Withdraws amt from bank account. * @throw AccountException thrown if amt > available balance */ public void withdraw(double amt) throws AccountException { System.out.println("withdraw(" + amt + ") called."); if (amt > balance) { throw new AccountException("Your balance is " + balance + "! You cannot withdraw " + amt + "!"); } balance -= amt; } // Getter/setter methods on Entity Bean fields public double getBalance() { System.out.println("getBalance() called."); return balance; } public void setOwnerName(String name) { System.out.println("setOwnerName() called."); ownerName = name; } public String getOwnerName() { System.out.println("getOwnerName() called."); return ownerName; } public String getAccountID() { System.out.println("getAccountID() called."); return accountID; } public void setAccountID(String id) { System.out.println("setAccountID() called."); this.accountID = id; } /** * This home business method is independent of any * particular account instance. It returns the total * of all the bank accounts in the bank. */ public double ejbHomeGetTotalBankValue() throws AccountException { PreparedStatement pstmt = null; Connection conn = null; try { System.out.println("ejbHomeGetTotalBankValue()"); /* * Acquire DB connection */ conn = getConnection(); /* * Get the total of all accounts */ pstmt = conn.prepareStatement("select sum(balance) as total from accounts"); ResultSet rs = pstmt.executeQuery(); /* * Return the sum */ if (rs.next()) { return rs.getDouble("total"); } } catch (Exception e) { e.printStackTrace(); throw new AccountException(e); } finally { /* * Release DB Connection for other beans */ try { if (pstmt != null) pstmt.close(); } catch (Exception e) {} try { if (conn != null) conn.close(); } catch (Exception e) {} } throw new AccountException("Error!"); } // // EJB-required methods // /** * Called by Container. Implementation can acquire * needed resources. */ public void ejbActivate() { System.out.println("ejbActivate() called."); } /** * Removes entity bean data from the database. * Corresponds to when client calls home.remove(). */ public void ejbRemove() throws RemoveException { System.out.println("ejbRemove() called."); /* * Remember that an entity bean class can be used to * represent different data instances. So how does * this method know which instance in the database * to delete? * * The answer is to query the container by calling * the entity context object. By retrieving the * primary key from the entity context, we know * which data instance, keyed by the PK, that we * should delete from the DB. */ AccountPK pk = (AccountPK) ctx.getPrimaryKey(); String id = pk.accountID; PreparedStatement pstmt = null; Connection conn = null; try { /* * 1) Acquire a new JDBC Connection */ conn = getConnection(); /* * 2) Remove account from the DB */ pstmt = conn.prepareStatement("delete from accounts where id = ?"); pstmt.setString(1, id); /* * 3) Throw a system-level exception if something * bad happened. */ if (pstmt.executeUpdate() == 0) { throw new RemoveException("Account " + pk + " failed to be removed from the database"); } } catch (Exception ex) { throw new EJBException(ex.toString()); } finally { /* * 4) Release the DB Connection */ try { if (pstmt != null) pstmt.close(); } catch (Exception e) {} try { if (conn != null) conn.close(); } catch (Exception e) {} } } /** * Called by Container. Releases held resources for * passivation. */ public void ejbPassivate() { System.out.println("ejbPassivate () called."); } /** * Called by the container. Updates the in-memory entity * bean object to reflect the current value stored in * the database. */ public void ejbLoad() { System.out.println("ejbLoad() called."); /* * Again, query the Entity Context to get the current * Primary Key, so we know which instance to load. */ AccountPK pk = (AccountPK) ctx.getPrimaryKey(); String id = pk.accountID; PreparedStatement pstmt = null; Connection conn = null; try { /* * 1) Acquire a new DB Connection */ conn = getConnection(); /* * 2) Get account from the DB, querying * by account ID */ pstmt = conn.prepareStatement("select ownerName, balance from accounts where id = ?"); pstmt.setString(1, id); ResultSet rs = pstmt.executeQuery(); rs.next(); ownerName = rs.getString("ownerName"); balance = rs.getDouble("balance"); } catch (Exception ex) { throw new EJBException("Account " + pk + " failed to load from database", ex); } finally { /* * 3) Release the DB Connection */ try { if (pstmt != null) pstmt.close(); } catch (Exception e) {} try { if (conn != null) conn.close(); } catch (Exception e) {} } } /** * Called from the Container. Updates the database * to reflect the current values of this in-memory * entity bean instance. */ public void ejbStore() { System.out.println("ejbStore() called."); PreparedStatement pstmt = null; Connection conn = null; try { /* * 1) Acquire a new DB Connection */ conn = getConnection(); /* * 2) Store account in DB */ pstmt = conn.prepareStatement("update accounts set ownerName = ?, balance = ? where id = ?"); pstmt.setString(1, ownerName); pstmt.setDouble(2, balance); pstmt.setString(3, accountID); pstmt.executeUpdate(); } catch (Exception ex) { throw new EJBException("Account " + accountID + " failed to save to database", ex); } finally { /* * 3) Release the DB Connection */ try { if (pstmt != null) pstmt.close(); } catch (Exception e) {} try { if (conn != null) conn.close(); } catch (Exception e) {} } } /** * Called by the container. Associates this bean * instance with a particular context. We can query * the bean properties which customize the bean here. */ public void setEntityContext(EntityContext ctx) { System.out.println("setEntityContext called"); this.ctx = ctx; } /** * Called by Container. Disassociates this bean * instance with a particular context environment. */ public void unsetEntityContext() { System.out.println("unsetEntityContext called"); this.ctx = null; } /** * Called after ejbCreate(). Now, the Bean can retrieve * its EJBObject from its context, and pass it as * a 'this' argument. */ public void ejbPostCreate(String accountID, String ownerName) { } /** * This is the initialization method that corresponds to the * create() method in the Home Interface. * * When the client calls the Home Object's create() method, * the Home Object then calls this ejbCreate() method. * * @return The primary key for this account */ public AccountPK ejbCreate(String accountID, String ownerName) throws CreateException { PreparedStatement pstmt = null; Connection conn = null; try { System.out.println("ejbCreate() called."); this.accountID = accountID; this.ownerName = ownerName; this.balance = 0; /* * Acquire DB connection */ conn = getConnection(); /* * Insert the account into the database */ pstmt = conn.prepareStatement("insert into accounts (id, ownerName, balance) values (?, ?, ?)"); pstmt.setString(1, accountID); pstmt.setString(2, ownerName); pstmt.setDouble(3, balance); pstmt.executeUpdate(); /* * Generate the Primary Key and return it */ return new AccountPK(accountID); } catch (Exception e) { throw new CreateException(e.toString()); } finally { /* * Release DB Connection for other beans */ try { if (pstmt != null) pstmt.close(); } catch (Exception e) {} try { if (conn != null) conn.close(); } catch (Exception e) {} } } /** * Finds a Account by its primary Key */ public AccountPK ejbFindByPrimaryKey(AccountPK key) throws FinderException { PreparedStatement pstmt = null; Connection conn = null; try { System.out.println("ejbFindByPrimaryKey(" + key + ") called"); /* * Acquire DB connection */ conn = getConnection(); /* * Find the Entity in the DB */ pstmt = conn.prepareStatement("select id from accounts where id = ?"); pstmt.setString(1, key.toString()); ResultSet rs = pstmt.executeQuery(); rs.next(); /* * No errors occurred, so return the Primary Key */ return key; } catch (Exception e) { throw new FinderException(e.toString()); } finally { /* * Release DB Connection for other beans */ try { if (pstmt != null) pstmt.close(); } catch (Exception e) {} try { if (conn != null) conn.close(); } catch (Exception e) {} } } /** * Finds all Accounts by a name */ public Collection ejbFindByOwnerName(String name) throws FinderException { PreparedStatement pstmt = null; Connection conn = null; Vector v = new Vector(); try { System.out.println("ejbFindByOwnerName(" + name + ") called"); /* * Acquire DB connection */ conn = getConnection(); /* * Find the primary keys in the DB */ pstmt = conn.prepareStatement("select id from accounts where ownerName = ?"); pstmt.setString(1, name); ResultSet rs = pstmt.executeQuery(); /* * Insert every primary key found into a vector */ while (rs.next()) { String id = rs.getString("id"); v.addElement(new AccountPK(id)); } /* * Return the vector of primary keys */ return v; } catch (Exception e) { throw new FinderException(e.toString()); } finally { /* * Release DB Connection for other beans */ try { if (pstmt != null) pstmt.close(); } catch (Exception e) {} try { if (conn != null) conn.close(); } catch (Exception e) {} } } /** * Gets JDBC connection from the connection pool. * * @return The JDBC connection */ public Connection getConnection() throws Exception { try { Context ctx = new InitialContext(); javax.sql.DataSource ds = (javax.sql.DataSource) ctx.lookup("java:comp/env/jdbc/bmp-account"); return ds.getConnection(); } catch (Exception e) { System.err.println("Could not locate datasource! Reason:"); e.printStackTrace(); throw e; } } }