JBuilder2005 actual JSP login page (2)

Author：Eve Cole Update Time：2009-07-02 17:10:51

Through File->New...->Web->double-click the JSP icon, the dialog box for creating a JSP wizard will pop up, as shown in the following figure:

Figure 3 Create login.jsp through wizard

·Web module: If there are multiple Web modules under a project, you can specify the Web module to which JSP is added here. Because there is only one webModule in our project, the wizard will set it to webModule by default.

·Name: Type in the JSP file name. You can type in the .jsp suffix, or you can type login directly without the suffix.

After the Generate sample bean option is checked, JBuilder will generate a sample Bean and introduce the Bean in the JSP. For beginners, you can use this option to see how JSP references a Bean, and the Generate error page option will automatically create a matching error handling JSP file for JSP. Here, we do not check them.

Click Finish directly to create login.jsp. The login.jsp file appears in the compiler of the content pane, as shown in the following figure:

Figure 4 JSP file created by the wizard

There is one on the left and right sides of the JSP compilation window that can be passed

and

The vertical bar controlled by buttons. The left column is a panel for placing JSP tags and HTML tags. You can drag and drop various tags into the JSP file just like in the visual UI designer. As shown in the picture above, we select the form from the panel. HTML tags are placed in the login.jsp file.

The vertical column on the right is the attribute compiler of the label where the current cursor is located in the JSP file, as shown in the following figure:

Figure 5 Set JSP tag attribute editor

The property editor is dynamic. When the cursor is moved to different labels, the property editor displays all the settable properties of this label. As shown in the figure above, it corresponds to the attribute editor of the HTML form tag. We set its action attribute to switch.jsp and specify to use POST to send the request data.

We provide a username drop-down box, a password input box and a login submit button in login.jsp. The code is as follows:

Code Listing 4 login.jsp

1. ＜%@page contentType="text/html; charset=GBK" %＞
2. ＜html＞
3. ＜head＞
4. ＜title＞login＜/title＞
5. ＜/head＞
6. ＜body bgcolor="#ffffff"＞
7. ＜Form name="Form 1" method="post" action="switch.jsp"＞
8. User name: <select name="userId">
9. ＜option value="" selected＞--Login user--＜/option＞
10. ＜option value="100000"＞Jiang Ziya＜/option＞
11. ＜option value="100001"＞Bao Shuya＜/option＞
12. ＜option value="100002"＞Vertical teeth＜/option＞
13. ＜/select＞
14. Password: <input name="password" type="password">
15. ＜input type="submit" name="Submit" value="Login"＞
16. ＜/form＞
17. ＜/body＞
18. ＜/html＞

The form tag represents a form in a web page. The form can contain multiple components. After the web form is submitted, the data of these components is sent to the JSP file specified by the action attribute through the HTTP protocol for processing. Form data is generally sent via POST. The POST sending method has no limit on the amount of data and is more confidential.

The effect page of login.jsp is as shown below:

Figure 6 login.jsp entry page

Practical experience:

The JSP file code contains static and dynamic parts, that is, one part is HTML code, and the other part is JSP tags and Scriptlet code. JSP is generally a web page with dynamic logic. JBuilder supports dynamic code parts such as JSP tags and Scriptlets very well. You can use tools such as CodeInsight and TagInsight to complete coding quickly and correctly, and you can also compile and debug JSP. In terms of JSP static HTML code writing and visual design, JBuilder seems to be inadequate. Dreamweaver is obviously better than JBuilder in static code and visual design.

The complexity of things promotes division of labor, and the fine division of labor promotes professional development. When writing JSP, it is not that once you have JBuilder, you will have nothing else to do. Han Xinshanbing and Xiao Heshanmou, if you can combine Dreamweaver and JBuilder, use Dreamweaver to develop the visual part of JSP, and use JBuilder to develop the dynamic code part of JSP, the two will complement each other and complement each other, and the JSP development work will become more streamlined. .

Change user list to dynamic

The currently created login.jsp has a flaw. Assume that when adding other users to the T_USER table in the database background, because the user name drop-down box is a static code, the newly created user will not appear on the page, so it is necessary to add the user The name list is changed to dynamic code, and the records of the database table T_USER are used to dynamically generate the data of the drop-down box.

We complete this work through the UserList.ava class and create UserList.java in the project. The code is as follows:

Code Listing 5 UserList.java

1. package bookstore;
2. import java.sql.*;
3.
4. public class UserList
5. {
6. //Get the user list code of the HTML drop-down box
7. public static String getUserListHTML() {
8. Connection conn = null;
9. StringBuffer sBuf = new StringBuffer();
10. try {
11. conn = DBConnection.getConnection();
12. PreparedStatement pStat = conn.prepareStatement(
13. "select USER_ID,USER_NAME from T_USER");
14. ResultSet rs = pStat.executeQuery();
15. while (rs.next()) {
16. sBuf.append("＜option value='" + rs.getString("USER_ID") + "'＞" +
17. rs.getString("USER_NAME") + "＜/option＞n");
18. }
19. return sBuf.toString();
20. } catch (SQLException ex) {
21. ex.printStackTrace();
22. return "";
23. } finally {
24. try {
25. if (conn != null) {
26. conn.close();
27. conn = null;
28. }
29. } catch (SQLException ex1) {
30. }
31. }
32. }
33. }

UserList.java only provides a static getUserListHTML() method, which obtains user records from the T_USER table in the backend database and generates the option code for the HTML select component, as shown in lines 16 to 17.

After creating this class, we refer to this class to adjust the code of login.jsp. First, reference the UserList class through the import attribute in the page instruction tag, and then adjust the content in the select option to the value returned by the getUserListHTML() method, as shown in the figure below Show:

Figure 7 Writing code through CodeInsight

Replace the original static HTML code through expression tags. It is worth mentioning that you can also use CodeInsight to enter code in JSP just like writing general Java classes. The code for the adjusted login.jsp is as follows, in bold:

Code Listing 6: Adjusted login.jsp code

1. ＜%@page contentType="text/html; charset=GBK" import="bookstore.UserList" %＞
2. ＜html＞
3. ＜head＞
4. ＜title＞login＜/title＞
5. ＜/head＞
6. ＜body bgcolor="#ffffff"＞
7. <Form name="Form 1" method="post" action="switch.jsp">User name:
8. ＜select name="userId"＞
9. ＜option value="" selected＞--Login user--＜/option＞
10. ＜%=UserList.getUserListHTML()%＞
11. ＜/select＞
12. Password: <input name="password" type="password">
13. ＜input type="submit" name="Submit" value="Login"＞
14. ＜/form＞
15. ＜/body＞
16. ＜/html＞

After saving login.jsp, right-click in the login.jsp file label in the content pane and select Web Run using Defaults. JBuilder will start the Tomcat 5.0 application server, run on port 8080, compile and run the login.jsp file, as shown in the figure below Show:

Figure 8 Running login.jsp in JBuilder

JBuilder automatically switches to the Web View page to display the running effect of the page. However, JBuilder's browser has very weak support for web pages and does not support JavaScript scripts. Therefore, after running login.jsp, it is best to view the effect of the web page through IE. You only need to open IE and copy the address of access login.jsp in JBuilder to the address bar of IE, as shown in the figure below. :

Figure 9 Use IE to access login.jsp running in JBuilder

At this time, the users in the drop-down box of the user name are already in the dynamic user list. When users are added or deleted in the T_USER table, the users in the drop-down box will also change accordingly.

Before running JSP, it is best to compile this JSP file separately: right-click on the JSP file label in the content pane and select make "xxx.jsp" in the pop-up menu to complete the compilation of the JSP file and discover it in time. mistake. When editing JSP files and Java files, the biggest difference is that any errors in Java program files will be listed in the editor and structure pane, but some errors in JSP files need to be compiled to be discovered.

hint:

Since compiling a JSP file requires first converting it into a Servlet file, and then compiling the intermediate Servlet file. If an error occurs, it will be redirected to the JSP file. Therefore, compiling a JSP file is more time-consuming and often takes longer than compiling a Java file. Several times the time. By default, when compiling a project, all JSPs in the entire project will be compiled, which takes a lot of time. Therefore, it is best to cancel the setting of compiling JSP files together with the compilation project: through Project->Project Properties...->Build-> cancel the Check JSPs for errors at build-time option in the Build settings page. Check this option when you really need it, and cancel this option immediately after compilation. This setting will buy you a lot of valuable time in development.