Java Server Pages. JSP Part II

Transcription

1 Java Server Pages JSP Part II

2 Agenda Actions Beans JSP & JDBC MVC 2

3 Components Scripting Elements Directives Implicit Objects Actions 3

4 Actions Actions are XML-syntax tags used to control the servlet engine Action elements are basically predefined functions <jsp:action_name attribute="value" /> 4

5 Standard Actions JSP Action Tags jsp:forward jsp:include jsp:usebean jsp:setproperty jsp:getproperty jsp:plugin jsp:param Description forwards the request and response to another resource. includes another resource. creates or locates bean object. sets the value of property in bean object. prints the value of property of the bean. embeds another components such as applet. sets the parameter value. It is used in forward and include mostly. jsp:fallback can be used to print the message if plugin is working. It is used in jsp:plugin. 5

6 include directive and include action JSP include directive JSP include action includes resource at translation time. includes resource at request time. better for static pages. better for dynamic pages. includes the original content in the generated servlet. calls the include method. 6

7 Java Beans A component architecture for Java. Useful in JSP for encapsulating application logic and transferring data between pages. Beans are simply Java classes. 7

8 JavaBeans for programmers Beans must: Implement java.io.serializable Have a constructor with no argument Properties (a.k.a. alterable variables) must: Must have a get and set Must be private attributes 8

9 JavaBeans example package mybeans; import java.io.serializable; public class NameBean implements Serializable { private String fullname; public NameBean() { super(); name = new String("World"); } public void setfullname( String fullname ) { this.fullname = fullname; } public String getfullname() { return fullname; } } 9

10 <jsp:usebean> Locates or instantiates a JavaBeans components. <jsp:usebean id= beaninstancename scope= page request session application class= package.class /> Example: <jsp:usebean id= myname scope= page class= mybeans.namebean /> 10

11 <jsp:setproperty> Sets the value of one or more properties in a Bean, using the Bean s setter methods. Declare the Bean with <jsp:usebean> first <jsp:setproperty name= beaninstancename Example: property= propertyname value= string /> <jsp:usebean id= myname scope= page class= mybeans.namebean /> <jsp:setproperty name= myname property= fullname value= abc /> 11

12 <jsp:getproperty> Gets a Bean property value, using the Bean s getter methods. Declare the Bean with <jsp:usebean> <jsp:getproperty name= beaninstancename property= propertyname /> Example: <jsp:usebean id= myname scope= page class= mybeans.namebean /> <H1>My Name <jsp:getproperty name= myname property= fullname /> </H1> 12

13 Expression Language (EL) Simplifies the accessibility of data stored in the Java Bean component, and other objects like request, session, application etc. ${ expression } <form action="process.jsp"> Enter Name:<input type="text" name= input" /><br/><br/> <input type="submit" value="go"/> </form> Welcome, ${ param.input } 13

14 Implicit Objects in EL Implicit Objects pagescope requestscope sessionscope applicationscope param paramvalues header headervalues cookie initparam pagecontext Usage it maps the given attribute name with the value set in the page scope it maps the given attribute name with the value set in the request scope it maps the given attribute name with the value set in the session scope it maps the given attribute name with the value set in the application scope it maps the request parameter to the single value it maps the request parameter to an array of values it maps the request header name to the single value it maps the request header name to an array of values it maps the given cookie name to the cookie value it maps the initialization parameter it provides access to many objects request, session etc. 14

15 Expression Language (EL) <% session.setattribute("user", abc"); %> Value is ${ sessionscope.user } <% Cookie ck=new Cookie("name", xyz"); response.addcookie(ck); %> Hello, ${cookie.name.value} 15

16 JSP & JDBC import="java.sql.*,java.util.*"%> <html> <body> <% try { Class.forName("com.mysql.jdbc.Driver"); Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/students", "root", "password"); Statement stmt = con.createstatement(); ResultSet rs = stmt.executequery("select * from btcse"); %> <table border=1 bgcolor="orange"> <% while (rs.next()) { %> <tr> <td><%=rs.getstring("enrollment_number")%></td> <td><%=rs.getstring("student_name")%></td> </tr> <% } con.close(); } catch (Exception e) { System.out.println(e); } %> 16

17 MVC: Model, View, Controller Model 1 Model 2 17

18 MVC 18

19 References

20 Thank you 20