javaweb项目_1

package dao; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import java.util.ArrayList; import java.util.List; import com.mysql.jdbc.Connection; import entity.Subject; public class SubjectDaoImpl implements SubjectDao { Connection conn = (Connection) DBConn.getConn(); @Override public boolean add(Subject subject) { boolean flag = false; try { String sql="insert tb_subject values('"+subject.getSubjectID()+"','" +subject.getSubjectTitle()+"','" +subject.getSubjectOptionA()+"','" +subject.getSubjectOptionB()+"','" +subject.getSubjectOptionC()+"','" +subject.getSubjectOptionD()+"','" +subject.getSubjectAnswer()+"','" +subject.getSubjectParse()+"')"; PreparedStatement pstmt = conn.prepareStatement(sql); int i = pstmt.executeUpdate(); pstmt.close(); conn.close(); if(i>0) { flag = true; } } catch (SQLException e) { e.printStackTrace(); } return flag; } @Override public List<Subject> selectall() { List<Subject> list = new ArrayList<Subject>(); try { String sql = "select * from tb_subject"; PreparedStatement pstmt = conn.prepareStatement(sql); ResultSet rs = pstmt.executeQuery(); while(rs.next()) { Subject subject = new Subject(); subject.setSubjectID(rs.getInt("subjectID")); subject.setSubjectTitle(rs.getString("subjectTitle")); subject.setSubjectOptionA(rs.getString("subjectOptionA")); subject.setSubjectOptionB(rs.getString("subjectOptionB")); subject.setSubjectOptionC(rs.getString("subjectOptionC")); subject.setSubjectOptionD(rs.getString("subjectOptionD")); subject.setSubjectAnswer(rs.getString("subjectAnswer")); subject.setSubjectParse(rs.getString("subjectParse")); list.add(subject); } rs.close(); pstmt.close(); conn.close(); } catch (SQLException e) { e.printStackTrace(); } return list; } @Override public List<Subject> selectByID(String subjectID) { List<Subject> list = new ArrayList<Subject>(); try { String sql = "select * from tb_subject where subjectID=?"; PreparedStatement pstmt = conn.prepareStatement(sql); pstmt.setString(1,subjectID ); ResultSet rs = pstmt.executeQuery(); while(rs.next()) { Subject subject = new Subject(); subject.setSubjectID(rs.getInt("subjectID")); subject.setSubjectTitle(rs.getString("subjectTitle")); subject.setSubjectOptionA(rs.getString("subjectOptionA")); subject.setSubjectOptionB(rs.getString("subjectOptionB")); subject.setSubjectOptionC(rs.getString("subjectOptionC")); subject.setSubjectOptionD(rs.getString("subjectOptionD")); subject.setSubjectAnswer(rs.getString("subjectAnswer")); subject.setSubjectParse(rs.getString("subjectParse")); list.add(subject); } rs.close(); pstmt.close(); conn.close(); } catch (SQLException e) { e.printStackTrace(); } return list; } @Override public boolean update( String subjectTitle, String subjectOptionA, String subjectOptionB, String subjectOptionC, String subjectOptionD, String subjectAnswer, String subjectParse) { boolean flag = false; try { String sql = "update tb_subject set subjectOptionA = '"+subjectOptionA+"',subjectOptionB = '"+subjectOptionB+"',subjectOptionC = '"+subjectOptionC+ "',subjectOptionD = '"+subjectOptionD+"',subjectAnswer = '"+subjectAnswer+"',subjectParse = '"+subjectParse+"' where subjectTitle = '"+subjectTitle+"'"; PreparedStatement pstmt = conn.prepareStatement(sql); int i = pstmt.executeUpdate(); pstmt.close(); conn.close(); if(i>0)flag = true; } catch (SQLException e) { e.printStackTrace(); } return flag; } @Override public boolean delete(int subjectID) { boolean flag = false; try { String sql = "delete from tb_subject where subjectID = '"+subjectID+"'"; PreparedStatement pstmt = conn.prepareStatement(sql); int i = pstmt.executeUpdate(); pstmt.close(); conn.close(); if(i>0) flag = true; } catch (SQLException e) { System.out.println("删除失败！"); e.printStackTrace(); } return flag; } }