基于Java的实例源码-EJB的真实世界模型（源代码）.zip

//实现Enroll的具体功能 package enroll.ejb; //download by http://www.codefans.net import java.sql.*; import javax.sql.*; import java.util.*; import javax.ejb.*; import javax.naming.*; public class EnrollEJB implements EntityBean{ public String student_id; public ArrayList courseItems; private Connection con; private String dbJndi="java:comp/env/jdbc/ExampleDB"; private String dbId="guest"; private String dbPassword="guest123"; private EntityContext context; public void setEntityContext(EntityContext context){ this.context=context; try{ getConnection(); }catch(Exception ex){ throw new EJBException( "Connect to DB failed:"+ex.getMessage()); } } public void unsetEntityContext(){ try{ con.close(); }catch(SQLException ex){ throw new EJBException( "Close DB Connection failed:"+ex.getMessage()); } } public String ejbCreate( String student_id, ArrayList courseItems) throws CreateException{ if(courseItems==null||courseItems.size()==0) throw new CreateException( "ejbCreate exception : no any item"); this.student_id=student_id; try{ enroll(courseItems); }catch(Exception ex){ throw new EJBException( "ejbCreate exception: "+ex.getMessage()); } this.courseItems=courseItems; return student_id; } public void ejbPostCreate( String student_id, ArrayList courseItems){ } public String ejbFindByPrimaryKey(String student_id) throws ObjectNotFoundException, FinderException{ try{ if(!selectByStudentId(student_id)) throw new ObjectNotFoundException( student_id + "not found!"); }catch(Exception ex){ throw new FinderException( "ejbFindByPrimaryKey exception:"+ ex.getMessage()); } return student_id; } public Collection ejbFindAll() throws FinderException { Collection result; try{ result=selectAll(); }catch(Exception ex){ throw new FinderException(ex.getMessage()); } if(result.isEmpty()){ throw new ObjectNotFoundException("No rows found."); }else{ return result; } } public ArrayList getCourseItems(){ return courseItems; } public String getStudent_id(){ return student_id; } public void replaceCourseItems(ArrayList courseItems){ if(courseItems==null||courseItems.size()==0) throw new EJBException( "replaceCourseItems exception : no any item"); try{ unenroll(); enroll(courseItems); }catch(Exception ex){ throw new EJBException( "ejbLoad exception:"+ex.getMessage()); } this.courseItems=courseItems; } public void ejbLoad(){ try{ loadCourses(); }catch(Exception ex){ throw new EJBException( "ejbLoad exception:"+ex.getMessage()); } } public void ejbStore(){ } public void ejbActivate(){ student_id=(String)context.getPrimaryKey(); } public void ejbPassivate(){ student_id=null; } public void ejbRemove(){ try{ unenroll(); }catch(Exception ex){ throw new EJBException( "ejbRemove exception:"+ex.getMessage()); } } //============================================= //取得资料库连结 private void getConnection() throws NamingException, SQLException{ InitialContext ic=new InitialContext(); DataSource ds=(DataSource) ic.lookup(dbJndi); con= ds.getConnection(dbId, dbPassword); } private void enroll(ArrayList courseItems) throws SQLException{ String insertStatement = "insert into EnrollTBL values(? ,?)"; PreparedStatement ps= con.prepareStatement(insertStatement); try{ //逐笔将选课项目新增至EnrollTBL表格 ps.setString(1, this.student_id); for(int i=0; i<courseItems.size(); i++){ String course_id=(String)courseItems.get(i); ps.setString(2, course_id); ps.executeUpdate(); } }finally{ ps.close(); } } private boolean selectByStudentId(String student_id) throws SQLException{ String sqlStatement= "select distinct student_id from EnrollTBL "+ "where student_id=?"; PreparedStatement ps= con.prepareStatement(sqlStatement); try{ ps.setString(1, student_id); ResultSet rs=ps.executeQuery(); if(rs.next()) return true; return false; }finally{ ps.close(); } } private void unenroll() throws SQLException{ String deleteStatement = "delete from EnrollTBL "+ "where student_id=?"; PreparedStatement ps = con.prepareStatement(deleteStatement); try{ ps.setString(1, student_id); ps.executeUpdate(); }finally{ ps.close(); } } private void loadCourses() throws SQLException{ String selectStatement = "select course_id "+ "from EnrollTBL where student_id=? "; PreparedStatement ps= con.prepareStatement(selectStatement); try{ ps.setString(1, student_id); ResultSet rs=ps.executeQuery(); courseItems=new ArrayList(); while(rs.next()){ String course_id=rs.getString(1); courseItems.add(course_id); } }finally{ ps.close(); } } private Collection selectAll() throws SQLException{ String sqlStatement= "select distinct student_id " + "from EnrollTBL order by student_id"; PreparedStatement ps= con.prepareStatement(sqlStatement); try{ ResultSet rs=ps.executeQuery(); ArrayList al=new ArrayList(); while(rs.next()){ String id=rs.getString(1); al.add(id); } return al; }finally{ ps.close(); } } }