5. Programación en datos estructurados

   1:Example 8.1     CustomerTO.java: Transfer Object Used by CustomerDAO and Its Clients
   2:package com.corej2eepatterns.to;
   3:
   4:public class CustomerTO implements java.io.Serializable {
   5:        private String id;
   6:        private String name;
   7:        private String address;
   8:        . . .
   9:
  10:        public String getId(){ return id; }
  11:        public void setId(String id){ this.id = id; }
  12:        public String getName(){ return name; }
  13:        public void setName(String name){ this.name = name; }
  14:        public String getAddress(){ return address; }
  15:        public void setAddress(String address){
  16:                this.address = address;
  17:        }
  18:        // other getters and setters
  19:        . . . 
  20:}

   1:Example 8.2     CustomerDAO.java: Data Access Object
   2:package com.corej2eepatterns.dao;
   3:
   4:// imports
   5:
   6:public class CustomerDAO {
   7:        protected static final String FIELDS_INSERT = 
   8:                        "customer_name, customer_address, " + 
   9:                        "customer_contact, customer_phone, customer_email";
  10:
  11:        protected static final String FIELDS_RETURN = 
  12:                        "customer_id, " + FIELDS_INSERT;
  13:
  14:        protected static String INSERT_SQL =
  15:                        "insert into customer ( " + FIELDS_INSERT +
  16:                        " ) " + "values ( ?, ?, ?, ?, ?)";
  17:
  18:        protected static String SELECT_SQL = "select " +
  19:                        FIELDS_RETURN +
  20:                        " from customer where customer_id = ? ";
  21:
  22:        protected static String UPDATE_SQL =
  23:                        "update customer set customer_name = ?, " +
  24:                        "customer_address = ?, customer_contact = ?, " +
  25:                        "customer_phone = ?, customer_email = ? " +
  26:                        "where customer_id = ? ";
  27:
  28:        protected static String DELETE_SQL =
  29:                        "delete from Customer where customer_id = ? ";
  30:
  31:        // the data source used to connect to the back-end database
  32:        private DataSource datasource;
  33:
  34:        public CustomerDAO() throws DAOException {
  35:                try {
  36:                        // Shown here for clarity only. Typically, looking
  37:                        // up a data source is done by a Service Locator
  38:                        // and the DAO just uses the Service Locator to
  39:                        // obtain a data source.
  40:                        InitialContext initialContext =
  41:                                        new InitialContext();
  42:                        datasource = (DataSource) initialContext.lookup(
  43:                                        OracleDAOFactory.DATASOURCE_DB_NAME);
  44:                } catch (NamingException e) {
  45:                        throw new DAOException (
  46:                                        "Cannot locate data source at " + 
  47:                                        DAOFactory.DATASOURCE_DB_NAME, e);
  48:                }
  49:        }
  50:
  51:        public String create(CustomerTO cust) throws DAOException {
  52:                // initialize variables
  53:                Connection con = getConnection();
  54:                String customerId = null;
  55:
  56:                PreparedStatement prepStmt = null;
  57:                try {
  58:                        // create and setup statement
  59:                        prepStmt = con.prepareStatement(INSERT_SQL);
  60:                        int i = 1;
  61:                        prepStmt.setString(i++, cust.getName());
  62:                        prepStmt.setString(i++, cust.getAddress());
  63:                        . . .
  64:
  65:                        // execute the statement
  66:                        prepStmt.executeUpdate();
  67:
  68:                        // obtain the newly created customer id value
  69:                        . . .
  70:
  71:                } catch (Exception e) {
  72:                        // handle exception
  73:                } finally {
  74:                        // close connections
  75:                }
  76:
  77:                // return the newly created customer id value
  78:                return customerId;
  79:        }
  80:
  81:        public CustomerTO find(String customerId)
  82:                throws DAOException {
  83:                // initialize variables
  84:                CustomerTO cust = null;
  85:                Connection con = getConnection();
  86:                PreparedStatement prepStmt = null;
  87:                ResultSet rs = null;
  88:
  89:                try {
  90:                        // setup statement and retrieve results
  91:                        prepStmt = con.prepareStatement(SELECT_SQL);
  92:                        prepStmt.setString(1, customerId);
  93:                        rs = prepStmt.executeQuery();
  94:                        if (rs.next()) {
  95:                                //create the transfer object using data from rs
  96:                                cust = new CustomerTO();
  97:                                cust.setId(rs.getString(1));
  98:                                cust.setName(rs.getString(2));
  99:                                . . . 
 100:                        }
 101:                } catch (Exception e) {
 102:                        // handle exception
 103:                } finally {
 104:                        // close connections
 105:                }
 106:                return cust;
 107:        }
 108:
 109:        public void update(CustomerTO cust) throws DAOException {
 110:                Connection con = null;
 111:                PreparedStatement prepStmt = null;
 112:                try {
 113:                        // prepare statement
 114:                        con = getConnection();
 115:
 116:                        prepStmt = con.prepareStatement(UPDATE_SQL);
 117:                        int i = 1;
 118:
 119:                        // add fields first
 120:                        prepStmt.setString(i++, cust.getName());
 121:                        prepStmt.setString(i++, cust.getAddress());
 122:                        . . .
 123:
 124:                        // now add where parameters
 125:                        prepStmt.setString(i++, cust.getId());
 126:                        int rowCount = prepStmt.executeUpdate();
 127:                        prepStmt.close();
 128:                        if (rowCount == 0) {
 129:                                throw new DAOException(
 130:                                        "Update Error:Customer Id:" + cust.getId());
 131:                        }
 132:                } catch (Exception e) {
 133:                        // handle exception
 134:                } finally {
 135:                        // close connections
 136:                }
 137:        }
 138:
 139:        public void delete(String customerId) throws Exception {
 140:                // setup variables
 141:                Connection con = getConnection();
 142:                PreparedStatement prepStmt = null;
 143:
 144:                try {
 145:                        // execute database update
 146:                        prepStmt = con.prepareStatement(DELETE_SQL);
 147:                        prepStmt.setString(1, customerId);
 148:                        prepStmt.executeUpdate();
 149:                } catch (Exception e) {
 150:                        // handle exception
 151:                } finally {
 152:                        // close connections
 153:                }
 154:        }
 155:
 156:        // other methods for finders, etc.
 157:        . . .
 158:}