 J2ee Technologies: Integrate Servlet, Jndi , Jdbc, J2EE Web App using Servlet |
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 Feb 28 2005, 08:44 PM
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Newbie  Group: Members Posts: 8 Joined: 28-February 05 Member No.: 4,041  |
J2EE Technologies: Integrate Servlet, JNDI , JDBC and RDBMS Abstract: This example shows you how to use a Servlet to lookup a JDBC connection via JNDI, then connect to a database, and display content of a database table. Tools: SunOne App Server, PointBase database Download J2SE, J2EE SDKs from java.sun.com Suppose that you install SunOne App Server in D:\Sun I. Prepare the database: Start the PointBase database server: QUOTE ================== D:\Sun\AppServer\pointbase\tools\serveroption>startserver Server started, listening on port 9092, display level: 0 ... > Create an XML file to build with asant, to create database and table: Place build.xml in a directory called MyTestDB ================================== QUOTE <?xml version="1.0" ?> <!-- A minimal build.xml to populate a PointBase database. This is derived from the build.xml in the J2EE Tutorial. --> <project name = "studentDB" default="create-db_common" basedir="."> <property file="build.properties"/> <path id="db.classpath"> <fileset dir="${db.root}/lib"> <include name="*.jar"/> </fileset> </path> <target name="create-db_common" depends="init" description="Create database tables and populate database." > <java classname="com.pointbase.tools.toolsCommander" fork="yes" > <jvmarg line="${db.jvmargs}" /> <arg line="${db.driver} ${db.url} ${sql.script} ${db.user} ${db.pwd}" /> <classpath refid="db.classpath" /> </java> </target> <target name="init"> <tstamp/> </target> </project> Include the file build.properties in the same directory ====================================== QUOTE j2ee.home=D:/Sun/AppServer sunone.home=${j2ee.home} domain.resources="domain.resources" domain.resources.port=8080 db.root=${j2ee.home}/pointbase db.driver=com.pointbase.jdbc.jdbcUniversalDriver db.host=localhost db.port=9092 db.sid=sun-appserv-samples db.url=jdbc:pointbase:server://${db.host}:${db.port}/${db.sid} db.user=pbpublic db.pwd=pbpublic url.prop=DatabaseName ds.class=com.pointbase.jdbc.jdbcDataSource db.jvmargs=-ms16m -mx32m sql.script=student.sql Include a file student.sql in the same directory ================================= QUOTE CREATE TABLE student (name VARCHAR(10), qpa VARCHAR(6)); DELETE FROM student; INSERT INTO student VALUES('Sue', '4.0'); INSERT INTO student VALUES('Billy','3.4'); Execute the build.xml script with asant (Application Server Ant) ============================================== QUOTE D:\Java\MyTestDB>asant Buildfile: build.xml init: create-db_common: [java] ***************************************************************** [java] -driver com.pointbase.jdbc.jdbcUniversalDriver [java] -url jdbc:pointbase:server://localhost:9092/sun-appserv-samples [java] -script student.sql [java] -user pbpublic [java] -password pbpublic [java] -autocommit true [java] -prompt2 true [java] -spoolfile <none> [java] -silent false [java] ***************************************************************** [java] SQL> CREATE TABLE student [java] (name VARCHAR(10), qpa VARCHAR(6)); [java] OK [java] SQL> DELETE FROM student; [java] OK [java] SQL> INSERT INTO student VALUES('Sue', '4.0'); [java] 1 row(s) affected [java] SQL> INSERT INTO student VALUES('Billy','3.4'); [java] 1 row(s) affected BUILD SUCCESSFUL Total time: 2 seconds See if the database was created in PointBase =============================== Run the console with QUOTE D:\Sun\AppServer\pointbase\tools\serveroption>startconsole In the URL field be sure to select jdbc:pointbase:server://localhost/sun-appserv-samples User name pbpublic Password pbpublic Select OK and you should see SCHEMAS and SECURITY Schemas->PBPUBLIC->Tables->Select Student In "Enter SQL Commands" enter select * from student Click the Execute button (not the tab) II. Display database on the Web 1) Create a DataSource in the Application Server ================================= Start the app server (default server not sample server) Run the admin console. Expand JDBC and select the JDBC Resource Click new. Enter jdbc/PBPUBLIC as the JNDI name Choose PointBasePool in the pool name drop down list Click OK We have just associated a name with a connection pool. The name is a JNDI name. “JNDI” stands for the Java Naming and Directory Interface. We have bound a people friendly name to a database resource that provides a connection to our student database. 2) Write a servlet that reads the database and writes HTML to a browser ================================================= Compile the servlet called ReadStudentDB.java QUOTE // ReadStudentDB.java.java import java.io.*; import javax.servlet.*; import javax.servlet.http.*; import java.sql.*; import javax.sql.*; import javax.naming.*; import java.util.*; public class ReadStudentDB extends HttpServlet { public void doGet(HttpServletRequest req, HttpServletResponse response) throws ServletException, IOException { Connection con = null; try { InitialContext ic = new InitialContext(); Context envCtx = (Context) ic.lookup("java:comp/env"); DataSource ds = (DataSource) envCtx.lookup("jdbc/StudentDB"); con = ds.getConnection(); response.setContentType("text/html"); PrintWriter out = response.getWriter(); String resultString = ""; String selectStatement = "select * " + "from student"; PreparedStatement prepStmt = con.prepareStatement(selectStatement); ResultSet rs = prepStmt.executeQuery(); resultString += "<html><body>"; while (rs.next()) { resultString += rs.getString(1)+"<p>"; resultString += rs.getString(2)+"<p>"; } resultString += "</body></html>"; prepStmt.close(); out.println(resultString); } catch (SQLException ex) { System.out.println("SQL EX " + ex.getMessage()); } catch(Exception ex) { System.out.println(" A Wierd Exception " + ex); } finally { try { if(con != null) con.close(); } catch(SQLException e){ System.out.println("Problem closing"); } } } } Compile the servlet with the command javac ReadStudentDB.java. Go to the directory D:\Sun\AppServer\bin, run the command: QUOTE D:\Sun\AppServer\bin>deploytool Deploytool ->File->New Web Component Browse to the directory where the servlet resides and enter that directory path in the WAR location text box. This path will end with MyDBReader.war The war file MyDBReader (without the .war) will be automatically placed in the WAR name text box. Set the context root to /GetStudents (this will be the name that appears after http://localhost:8080/ on the browser) Edit Contents and place the compiled servlet in the WAR Complete the wizard, select the servlet from the tree to the left, select the alias tab and give it the alias /CoolServlet. Don’t forget to hit the return key. (This will be the name that appears after http://localhost:8080/GetStudents/ on the browser.) Select the WAR name on the tree to the left. Select the Resource Ref’s tab Click Add Type jdbc/StudentDB in the coded name field (don’t forget the return key). The “coded name” must be the same with the name in the servlet’s code: DataSource ds = (DataSource) envCtx.lookup("jdbc/StudentDB"); Select localhost:4848 in the server list (log in if you must) Select MyDBReader in the web war list Select the Resource Ref’s tab Select the Resource Reference Name, jdbc/StudentDB, that you just entered In the Sun-specifi settings frame, select jdbc/StudentDB from the Drop Down List for the JNDI name In the User Name text field enter pbpublic (this is the database user name) In the Password Field enter pbpublic (this is the database password) Deploy the web application III.Testing Make sure the database is running Make sure the Application Server is running Make sure MyDBReader.war is deployed Use a browser to visit http://localhost:8080/GetStudents/CoolServlet |
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