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1
27
28 package enroller;
29
30 import java.rmi.RemoteException  ;
31 import javax.ejb.*;
32 import java.sql.*;
33 import javax.sql.*;
34 import java.util.*;
35 import javax.naming.*;
36
37
38 public class EnrollerBean implements SessionBean, EnrollerRemoteBusiness {
39 private static final String dbName = "jdbc/pointbase";
40 private Connection con;
41 private SessionContext context;
42
43 public EnrollerBean() {
44 }
45
46 public void enroll(String studentId, String courseId) {
47 try {
48 insertEntry(studentId, courseId);
49 } catch (Exception ex) {
50 throw new EJBException("enroll: " + ex.getMessage());
51 }
52 }
53
54 public void unEnroll(String studentId, String courseId) {
55 try {
56 deleteEntry(studentId, courseId);
57 } catch (Exception ex) {
58 throw new EJBException("unEnroll: " + ex.getMessage());
59 }
60 }
61
62 public void deleteStudent(String studentId) {
63 try {
64 deleteStudentEntries(studentId);
65 } catch (Exception ex) {
66 throw new EJBException("deleteStudent: " + ex.getMessage());
67 }
68 }
69
70 public void deleteCourse(String courseId) {
71 try {
72 deleteCourseEntries(courseId);
73 } catch (Exception ex) {
74 throw new EJBException("deleteCourse: " + ex.getMessage());
75 }
76 }
77
78 public ArrayList getStudentIds(String courseId) {
79 try {
80 return selectStudent(courseId);
81 } catch (Exception ex) {
82 throw new EJBException("getStudentIds: " + ex.getMessage());
83 }
84 }
85
86 public ArrayList getCourseIds(String studentId) {
87 try {
88 return selectCourse(studentId);
89 } catch (Exception ex) {
90 throw new EJBException("getCourseIds: " + ex.getMessage());
91 }
92 }
93
94 public void ejbCreate() {
95 }
96
97 public void ejbRemove() {
98 }
99
100 public void ejbActivate() {
101 }
102
103 public void ejbPassivate() {
104 }
105
106 public void setSessionContext(SessionContext context) {
107 this.context = context;
108 }
109
110
111 private void makeConnection() {
112 try {
113 InitialContext ic = new InitialContext();
114 DataSource ds = (DataSource) ic.lookup(dbName);
115
116 con = ds.getConnection();
117 } catch (Exception ex) {
118 throw new EJBException("Unable to connect to database. " +
119 ex.getMessage());
120 }
121 }
122
123 private void releaseConnection() {
124 try {
125 con.close();
126 } catch (SQLException ex) {
127 throw new EJBException("releaseConnection: " + ex.getMessage());
128 }
129 }
130
131 private void insertEntry(String studentId, String courseId)
132 throws SQLException {
133 makeConnection();
134
135 String insertStatement = "insert into enrollment values ( ? , ? )";
136 PreparedStatement prepStmt = con.prepareStatement(insertStatement);
137
138 prepStmt.setString(1, studentId);
139 prepStmt.setString(2, courseId);
140
141 prepStmt.executeUpdate();
142 prepStmt.close();
143 releaseConnection();
144 }
145
146 private void deleteEntry(String studentId, String courseId)
147 throws SQLException {
148 makeConnection();
149
150 String deleteStatement =
151 "delete from enrollment " + "where studentid = ? and courseid = ?";
152 PreparedStatement prepStmt = con.prepareStatement(deleteStatement);
153
154 prepStmt.setString(1, studentId);
155 prepStmt.setString(2, courseId);
156 prepStmt.executeUpdate();
157 prepStmt.close();
158 releaseConnection();
159 }
160
161 private void deleteStudentEntries(String studentId)
162 throws SQLException {
163 makeConnection();
164
165 String deleteStatement =
166 "delete from enrollment " + "where studentid = ?";
167 PreparedStatement prepStmt = con.prepareStatement(deleteStatement);
168
169 prepStmt.setString(1, studentId);
170 prepStmt.executeUpdate();
171 prepStmt.close();
172 releaseConnection();
173 }
174
175 private void deleteCourseEntries(String courseId) throws SQLException {
176 makeConnection();
177
178 String deleteStatement =
179 "delete from enrollment " + "where courseid = ?";
180 PreparedStatement prepStmt = con.prepareStatement(deleteStatement);
181
182 prepStmt.setString(1, courseId);
183 prepStmt.executeUpdate();
184 prepStmt.close();
185 releaseConnection();
186 }
187
188 private ArrayList selectStudent(String courseId) throws SQLException {
189 makeConnection();
190
191 String selectStatement =
192 "select studentid " + "from enrollment where courseid = ? ";
193 PreparedStatement prepStmt = con.prepareStatement(selectStatement);
194
195 prepStmt.setString(1, courseId);
196
197 ResultSet rs = prepStmt.executeQuery();
198 ArrayList a = new ArrayList();
199
200 while (rs.next()) {
201 String id = rs.getString(1);
202
203 a.add(id);
204 }
205
206 prepStmt.close();
207 releaseConnection();
208
209 return a;
210 }
211
212 private ArrayList selectCourse(String studentId) throws SQLException {
213 makeConnection();
214
215 String selectStatement =
216 "select courseid " + "from enrollment where studentid = ? ";
217 PreparedStatement prepStmt = con.prepareStatement(selectStatement);
218
219 prepStmt.setString(1, studentId);
220
221 ResultSet rs = prepStmt.executeQuery();
222 ArrayList a = new ArrayList();
223
224 while (rs.next()) {
225 String id = rs.getString(1);
226
227 a.add(id);
228 }
229
230 prepStmt.close();
231 releaseConnection();
232
233 return a;
234 }
235 }
236 |
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