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Java > Open Source Codes > example > cmp > many2many > CollectionServlet


1 package example.cmp.many2many;
2
3 import javax.servlet.*;
4 import javax.servlet.http.*;
5
6 import javax.ejb.*;
7
8 import javax.naming.*;
9
10 import java.util.Collection;
11 import java.util.Iterator;
12
13 import java.io.PrintWriter;
14
15 /**
16  * A client to illustrate EJB managed relations in a many-to-many context.
17  */
18 public class CollectionServlet extends HttpServlet {
19   StudentHome studentHome;
20   CourseHome courseHome;
21
22   /**
23    *
24    */
25   public void init()
26     throws ServletException
27   {
28     // obtain references to the home interfaces
29 try {
30       Context ejb = (Context)new InitialContext().lookup("java:comp/env/cmp");
31
32       // get the Student CMP-Bean home interface
33 studentHome = (StudentHome) ejb.lookup("many2many_StudentBean");
34
35       // get the Course CMP-Bean home interface
36 courseHome = (CourseHome) ejb.lookup("many2many_CourseBean");
37
38     } catch (NamingException e) {
39       throw new ServletException(e);
40     }
41   }
42
43   /**
44    *
45    */
46   public void service(HttpServletRequest req, HttpServletResponse res)
47     throws java.io.IOException, ServletException
48   {
49     res.setContentType("text/html");
50
51     PrintWriter out = res.getWriter();
52
53     // get references to all entities we will work with
54 Student student = null;
55     Course course = null;
56     try {
57       student = studentHome.findByPrimaryKey("Hermione Granger");
58       course = courseHome.findByPrimaryKey("Divination");
59     } catch (javax.ejb.FinderException e) {
60       throw new ServletException(e);
61     }
62
63     // one student can be enrolled in any number of courses...
64 out.println("<h3>" + student.getName() + "'s classes:</h3>");
65
66     // Show all courses the student is currently enrolled in
67 Iterator it = student.getCourseList().iterator();
68     while (it.hasNext())
69       out.println("<li> " + ((Course) it.next()).getName() );
70
71     // enrolling the student in the course
72 out.println("<p>Enrolling " + student.getName() + " in " +
73                 course.getName() + "\n");
74
75     student.addCourse(course);
76
77     // Show the change
78 out.println("<h3>" + student.getName() + "'s new classes:</h3>");
79     it = student.getCourseList().iterator();
80     while (it.hasNext())
81       out.println("<li> " + ((Course) it.next()).getName() );
82
83     student.removeCourse(course);
84
85     // Show the change
86 out.println("<h3>" + course.getName() + " students:</h3>");
87
88     // ...and a course can be taught to any number of students
89 it = course.getStudentList().iterator();
90     while (it.hasNext())
91       out.println("<li> " + ((Student) it.next()).getName());
92
93     // enroll the student in the course
94 out.println("<p>Enrolling " + student.getName() + " in " +
95                 course.getName());
96
97
98     course.addStudent(student);
99
100     // Show the change
101 out.println("<h3>" + course.getName() + " new students:</h3>");
102
103     // ...and a course can be taught to any number of students
104 it = course.getStudentList().iterator();
105     while (it.hasNext())
106       out.println("<li> " + ((Student) it.next()).getName());
107
108     // undo our steps so that the example will be worthwhile next time its run
109 course.removeStudent(student);
110   }
111 }
112
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