Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>You seem to be talking about using directly a database connection from your JSP files, don't you? Well, this is not a theoretically correct solution because following separation of concerns principle, your view -your JSP file- shouldn't know anything at all about databases or data access. Check any description of MVC pattern, for instance this pretty obvious ;-):</p> <p><a href="http://en.wikipedia.org/wiki/Model%E2%80%93view%E2%80%93controller" rel="nofollow noreferrer">Wikipedia on MVC pattern</a></p> <p>But if you want to take the shorcut and have your view aware of your database you have, in my opinion, two options, both of them involving the JNDI lookup of a datasource previously defined in your appplication as <a href="https://stackoverflow.com/users/1193148/marcelo-tataje">Marcelo Tataje</a> already said. </p> <p>On how to define on Tomcat a JNDI datasource based on a connection pool:</p> <p><a href="http://tomcat.apache.org/tomcat-6.0-doc/jndi-datasource-examples-howto.html" rel="nofollow noreferrer">http://tomcat.apache.org/tomcat-6.0-doc/jndi-datasource-examples-howto.html</a></p> <p>In the same page you can see how to use this connection pool to issue queries right from your JSP (again very inadvisable in my opinion)</p> <pre><code>&lt;%@ taglib uri="http://java.sun.com/jsp/jstl/sql" prefix="sql" %&gt; &lt;%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %&gt; &lt;sql:query var="rs" dataSource="jdbc/TestDB"&gt; select id, foo, bar from testdata &lt;/sql:query&gt; &lt;html&gt; &lt;head&gt; &lt;title&gt;DB Test&lt;/title&gt; &lt;/head&gt; &lt;body&gt; &lt;h2&gt;Results&lt;/h2&gt; &lt;c:forEach var="row" items="${rs.rows}"&gt; Foo ${row.foo}&lt;br/&gt; Bar ${row.bar}&lt;br/&gt; &lt;/c:forEach&gt; &lt;/body&gt; &lt;/html&gt; </code></pre> <p><a href="https://stackoverflow.com/questions/1531073/is-java-sql-connection-thread-safe">Is java.sql.Connection thread safe?</a></p> <p>The other slightly better solution is, in your java code, JNDI lookup the datasource like this from your context listener:</p> <pre><code> public void contextInitialized(ServletContextEvent contextEvent) { // JNDI Datasource lookup InitialContext context = new InitialContext(); DataSource dataSource = (DataSource) context .lookup("jdbc/DataSource"); // Storing datasource in application context contextEvent.getServletContext().setAttribute("datasource",dataSource); } </code></pre> <p>and after from any servlet use that stored datasource to get the database connection you need like this </p> <pre><code>((DataSource)contextEvent.getServletContext().getAttribute("datasource")).getConnection() </code></pre> <p>Don't use Connection class directly please. It's awfully primitive and obsolete. Nowadays nobody in a serious working environment handle connections like that. If you do what <a href="https://stackoverflow.com/users/1115584/amitg">AmitG</a> proposed you will end up with an unique connection shared by all concurrent accesses. See this on why this isn't the way to go</p>
    singulars
    1. This table or related slice is empty.
    1. POIs it possible to declare a global variable so that it can be used from every class in JSP?
      singulars
      1. PTQuestion
    1. PTAnswer
    1. USCommunity
    1. USpvm14
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. COI didn't talk about accessing db directly with JSP, i use a servlet to connect and do all queries
      singulars
      1. PO
      1. USBackSlash
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload