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我是java初学者，想在javabean中写几个方法，例如删，增，改，查询，但在写在bean的过程中，总是遇到很多麻烦，请大家指教！！！谢谢了，程序如下，现在的增加还有很多毛病，请大家帮助我一下！！！！
说来你是写的是实体Bean,
这样吧，我给你一个例子，对你有帮助：
//CustomerBean.java
import java.sql.*;
import javax.sql.*;
import java.util.*;
import javax.ejb.*;
import javax.naming.*;
public class CustomerBean implements EntityBean {
private String customerId;
private String salesRepId;
private String name;
private Connection con;
private String dbName = "java:comp/env/jdbc/SalesDB";
private EntityContext context;
public String getSalesRepId() {
return salesRepId;
}
public String getName() {
System.out.println("entering getName()");
return name;
}
public void setSalesRepId(String salesRepId) {
this.salesRepId = salesRepId;
}
public void setName(String name) {
this.name = name;
}
public String ejbCreate(String customerId, String salesRepId,
String name) throws CreateException {
System.out.println("in ejbCreate");
try {
insertCustomer(customerId, salesRepId, name);
} catch (Exception ex) {
throw new EJBException("ejbCreate: " +
ex.getMessage());
}
this.customerId = customerId;
this.salesRepId = salesRepId;
this.name = name;
System.out.println("about to leave ejbCreate");
return customerId;
}
public String ejbFindByPrimaryKey(String primaryKey)
throws FinderException {
boolean result;
try {
result = selectByPrimaryKey(primaryKey);
} catch (Exception ex) {
throw new EJBException("ejbFindByPrimaryKey: " +
ex.getMessage());
}
if (result) {
return primaryKey;
}
else {
throw new ObjectNotFoundException
("Row for id " + primaryKey + " not found.");
}
}
public Collection ejbFindBySalesRep(String salesRepId)
throws FinderException {
Collection result;
try {
result = selectBySalesRep(salesRepId);
} catch (Exception ex) {
throw new EJBException("ejbFindBySalesRep: " +
ex.getMessage());
}
return result;
}
public void ejbRemove() {
try {
deleteCustomer(customerId);
} catch (Exception ex) {
throw new EJBException("ejbRemove: " +
ex.getMessage());
}
}
public void setEntityContext(EntityContext context) {
this.context = context;
try {
makeConnection();
} catch (Exception ex) {
throw new EJBException("Unable to connect to database. " +
ex.getMessage());
}
}
public void unsetEntityContext() {
try {
con.close();
} catch (SQLException ex) {
throw new EJBException("unsetEntityContext: " + ex.getMessage());
}
}
public void ejbActivate() {
customerId = (String)context.getPrimaryKey();
}
public void ejbPassivate() {
customerId = null;
}
public void ejbLoad() {
System.out.println("in ejbLoad");
try {
loadCustomer();
} catch (Exception ex) {
throw new EJBException("ejbLoad: " +
ex.getMessage());
}
System.out.println("leaving ejbLoad");
}
public void ejbStore() {
System.out.println("in ejbStore");
try {
storeCustomer();
} catch (Exception ex) {
throw new EJBException("ejbStore: " +
ex.getMessage());
}
System.out.println("leaving ejbStore");
}
public void ejbPostCreate(String customerId, String salesRepId,
String name) { }
/*********************** Database Routines *************************/
private void makeConnection() throws NamingException, SQLException {
InitialContext ic = new InitialContext();
DataSource ds = (DataSource) ic.lookup(dbName);
con = ds.getConnection();
}
private void insertCustomer (String customerId, String salesRepId,
String name) throws SQLException {
String insertStatement =
"insert into customer values ( ? , ? , ? )";
PreparedStatement prepStmt =
con.prepareStatement(insertStatement);
prepStmt.setString(1, customerId);
prepStmt.setString(2, salesRepId);
prepStmt.setString(3, name);
prepStmt.executeUpdate();
prepStmt.close();
}
private boolean selectByPrimaryKey(String primaryKey)
throws SQLException {
String selectStatement =
"select customerid " +
"from customer where customerid = ? ";
PreparedStatement prepStmt =
con.prepareStatement(selectStatement);
prepStmt.setString(1, primaryKey);
ResultSet rs = prepStmt.executeQuery();
boolean result = rs.next();
prepStmt.close();
return result;
}
private Collection selectBySalesRep(String salesRepId)
throws SQLException {
String selectStatement =
"select customerid " +
"from customer where salesrepid = ? ";
PreparedStatement prepStmt =
con.prepareStatement(selectStatement);
prepStmt.setString(1, salesRepId);
ResultSet rs = prepStmt.executeQuery();
ArrayList a = new ArrayList();
while (rs.next()) {
String id = rs.getString(1);
a.add(id);
}
prepStmt.close();
return a;
}
private void deleteCustomer(String customerId) throws SQLException {
String deleteStatement =
"delete from customer " +
"where customerid = ?";
PreparedStatement prepStmt =
con.prepareStatement(deleteStatement);
prepStmt.setString(1, customerId);
prepStmt.executeUpdate();
prepStmt.close();
}
private void loadCustomer() throws SQLException {
String selectStatement =
"select customerid, salesRepid, name " +
"from customer where customerid = ? ";
PreparedStatement prepStmt =
con.prepareStatement(selectStatement);
prepStmt.setString(1, customerId);
ResultSet rs = prepStmt.executeQuery();
if (rs.next()) {
customerId = rs.getString(1);
salesRepId = rs.getString(2);
name = rs.getString(3);
prepStmt.close();
}
else {
prepStmt.close();
throw new NoSuchEntityException("Row for customerId " + customerId +
" not found in database.");
}
}
private void storeCustomer() throws SQLException {
System.out.println("entering storeCustomer");
String updateStatement =
"update customer " +
"set salesRepid = ? , name = ? " +
"where customerid = ?";
PreparedStatement prepStmt =
con.prepareStatement(updateStatement);
prepStmt.setString(1, salesRepId);
prepStmt.setString(2, name);
prepStmt.setString(3, customerId);
int rowCount = prepStmt.executeUpdate();
prepStmt.close();
if (rowCount == 0) {
throw new EJBException("Storing row for customerId " +
customerId + " failed.");
}
System.out.println("leaving storeCustomer");
}
} // CustomerBean
