private void deleteAddress() {
int id = addressPanel.getId();
if (id != -1) {
db.deleteRecord(id);
int selectedIndex = addressListPanel.deleteSelectedEntry();
...
}
...
}
在AddressDao里，deleteRecord方式实际上是从数据库删除一条记录。当第一次创建数据库连接时，AddressDao就创建了一个PreparedStatement。
stmtDeleteAddress = dbConnection.prepareStatement(
"DELETE FROM APP.ADDRESS " +
"WHERE ID = ?");
PreparedStatement可以使用多次，每次只需要一个参数就能确定删除哪条记录。在设置了ID参数后，deleteRecord方法执行Update。
public boolean deleteRecord(int id) {
boolean bDeleted = false;
try {
stmtDeleteAddress.clearParameters();
stmtDeleteAddress.setInt(1, id);
stmtDeleteAddress.executeUpdate();
bDeleted = true;
} catch (SQLException sqle) {
sqle.printStackTrace();
}
return bDeleted;
}
Edit按钮允许用户在AddressPanel里编辑当前选择的Address记录。在这个例子中，你可以修改记录的名字，城市或电话号码。
Save按钮要么是在AddressPanel里创建和编辑新的Address，要么就尝试编辑更新存在的记录。如果用户是编辑一个记录。Save按钮将使用新的信息来更新记录。如果用户是创建一个新的记录，Save按钮将插入一个新的记录到数据库。新的还没有被保存。这时，它的ID域仍然设置的是默认值-1。一旦你保存这条记录，这个值是自动生成的，并成为该记录的唯一标识。
下面是AddresFrame里的代码是通过调用DAO的editRecord或saveRecord方法来保存编辑后或新建的地址记录。当然，当你创建一条新记录，应用程序也必须更新AddressListPanel。
private void saveAddress() {
if (addressPanel.isEditable()) {
Address address = addressPanel.getAddress();
int id = address.getId();
if (id == -1) {
id = db.saveRecord(address);
address.setId(id);
String lname = address.getLastName();
String fname = address.getFirstName();
String mname = address.getMiddleName();
ListEntry entry = new ListEntry(lname, fname, mname, id);
addressListPanel.addListEntry(entry);
} else {
db.editRecord(address);
}
addressPanel.setEditable(false);
}
}
DAO的editRecord方法必须更新Address记录里更改的域。由于该应用程序示例不能分辨修改和未修改的域，它就更新了记录的所有域。下面是PreparedStatement对象和editRecord方法：
stmtUpdateExistingRecord = dbConnection.prepareStatement(
"UPDATE APP.ADDRESS " +
"SET LASTNAME = ?, " +
" FIRSTNAME = ?, " +
" MIDDLENAME = ?, " +
" PHONE = ?, " +
" EMAIL = ?, " +
" ADDRESS1 = ?, " +
" ADDRESS2 = ?, " +
" CITY = ?, " +
" STATE = ?, " +
" POSTALCODE = ?, " +
" COUNTRY = ? " +
"WHERE ID = ?");
...
public boolean editRecord(Address record) {
boolean bEdited = false;
try {
stmtUpdateExistingRecord.clearParameters();
stmtUpdateExistingRecord.setString(1, record.getLastName());
stmtUpdateExistingRecord.setString(2, record.getFirstName());
stmtUpdateExistingRecord.setString(3, record.getMiddleName());
stmtUpdateExistingRecord.setString(4, record.getPhone());
stmtUpdateExistingRecord.setString(5, record.getEmail());
stmtUpdateExistingRecord.setString(6, record.getAddress1());
stmtUpdateExistingRecord.setString(7, record.getAddress2());
stmtUpdateExistingRecord.setString(8, record.getCity());
stmtUpdateExistingRecord.setString(9, record.getState());
stmtUpdateExistingRecord.setString(10, record.getPostalCode());
stmtUpdateExistingRecord.setString(11, record.getCountry());
stmtUpdateExistingRecord.setInt(12, record.getId());
stmtUpdateExistingRecord.executeUpdate();
bEdited = true;
} catch(SQLException sqle) {
sqle.printStackTrace();
}
return bEdited;
}
