Java Web Programming Quick Reference

Forwarding a request using the dispatcher:
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RequestDispatcher dispatcher = getServletContext().getRequestDispatcher("next.jsp");
dispatcher.forward(request, response);


getParameter vs getAttribute
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request.getParameter("foo"); // read a URL parameter
request.getAttribute("bar"); // read an attribute that was set earlier


Accessing attribtues in JSP files
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<%@ page contentType="text/html" import="everything.you.need" %>
<jsp:useBean id="attributeId" scope="request" type="type.of.object"></jsp:useBean>


Including a file
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<jsp:include page="file.inc.jsp"/>


Creating a DB connection using the container's pool
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InitialContext ctx = new InitialContext();
Context envContext = (Context) ctx.lookup ("java:/comp/env");
DataSource ds = (DataSource) envContext.lookup("jdbc/mysql");
Connection con = ds.getConnection();

META-INF/context.xml:
<?xml version="1.0" encoding="UTF-8"?>
<Context path="/Enrolment_Recommender" docBase="Enrolment_Recommender"
	debug="1" reloadable="true" crossContext="true">
    <Resource name="jdbc/mysql" auth="Container" type="javax.sql.DataSource"
        driverClassName="com.mysql.jdbc.Driver" username="XXXXXXX" password="XXXXXXXX"
        url="jdbc:mysql://XXXXXXXXXXXXXXX:3306/XXXXXXX?autoReconnect=true"
        maxActive="8" maxIdle="3"
        removeAbandoned="true" removeAbandonedTimeout="180" />
</Context>


Using JDBC
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PreparedStatement stmt = con.prepareStatement("INSERT INTO ...");
stmt.setXXXX(1, foo);
stmt.executeUpdate();

PreparedStatement stmt = con.prepareStatement("SELECT ...");
stmt.setXXXX(1, foo);
ResultSet rs = stmt.executeQuery();
while (rs.next()) {
    rs.getXXXX("colname");
    ...
}
rs.close();