first commit for openGauss connector jdbc

docs/documentation/92/tomcat.md

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+---
+layout: default_docs
+title: Tomcat setup
+header: Chapter 11. Connection Pools and Data Sources
+resource: media
+previoustitle: Applications DataSource
+previous: ds-ds.html
+nexttitle: Data Sources and JNDI
+next: jndi.html
+---
+
+### Note
+
+The postgresql.jar file must be placed in $CATALINA_HOME/common/lib in both
+Tomcat 4 and 5.
+
+The absolute easiest way to set this up in either tomcat instance is to use the
+admin web application that comes with Tomcat, simply add the datasource to the
+context you want to use it in.
+
+Setup for Tomcat 4 place the following inside the <Context> tag inside
+conf/server.xml
+
+<pre><code>
+&lt;Resource name="jdbc/postgres" scope="Shareable" type="javax.sql.DataSource"/&gt;
+&lt;ResourceParams name="jdbc/postgres"&gt;
+	&lt;parameter&gt;
+		&lt;name&gt;validationQuery&lt;/name&gt;
+		&lt;value&gt;select version();&lt;/value&gt;
+	&lt;/parameter&gt;
+	&lt;parameter&gt;
+		&lt;name&gt;url&lt;/name&gt;
+		&lt;value&gt;jdbc:postgresql://localhost/davec&lt;/value&gt;
+	&lt;/parameter&gt;
+	&lt;parameter&gt;
+		&lt;name&gt;password&lt;/name&gt;
+		&lt;value&gt;davec&lt;/value&gt;
+	&lt;/parameter&gt;
+	&lt;parameter&gt;
+		&lt;name&gt;maxActive&lt;/name&gt;
+		&lt;value&gt;4&lt;/value&gt;
+	&lt;/parameter&gt;
+	&lt;parameter&gt;
+		&lt;name&gt;maxWait&lt;/name&gt;
+		&lt;value&gt;5000&lt;/value&gt;
+	&lt;/parameter&gt;
+	&lt;parameter&gt;
+		&lt;name&gt;driverClassName&lt;/name&gt;
+		&lt;value&gt;org.postgresql.Driver&lt;/value&gt;
+	&lt;/parameter&gt;
+	&lt;parameter&gt;
+		&lt;name&gt;username&lt;/name&gt;
+		&lt;value&gt;davec&lt;/value&gt;
+	&lt;/parameter&gt;
+	&lt;parameter&gt;
+		&lt;name&gt;maxIdle&lt;/name&gt;
+		&lt;value&gt;2&lt;/value&gt;
+	&lt;/parameter&gt;
+&lt;/ResourceParams&gt;	
+</code></pre>
+
+Setup for Tomcat 5, you can use the above method, except that it goes inside the
+&lt;DefaultContext&gt; tag inside the &lt;Host&gt; tag. eg. &lt;Host&gt; ... &lt;DefaultContext&gt; ...
+
+Alternatively there is a conf/Catalina/hostname/context.xml file. For example
+http://localhost:8080/servlet-example has a directory $CATALINA_HOME/conf/Catalina/localhost/servlet-example.xml file. 
+Inside this file place the above xml inside the &lt;Context&gt; tag
+
+Then you can use the following code to access the connection.
+
+<pre><code>
+import javax.naming.*;
+import javax.sql.*;
+import java.sql.*;
+public class DBTest 
+{
+
+	String foo = "Not Connected";
+	int bar = -1;
+    
+	public void init() 
+	{
+		try
+		{
+			Context ctx = new InitialContext();
+			if(ctx == null )
+				throw new Exception("Boom - No Context");
+	
+			// /jdbc/postgres is the name of the resource above 
+			DataSource ds = (DataSource)ctx.lookup("java:comp/env/jdbc/postgres");
+	    
+			if (ds != null) 
+			{
+				Connection conn = ds.getConnection();
+	    
+				if(conn != null) 
+				{
+					foo = "Got Connection "+conn.toString();
+					Statement stmt = conn.createStatement();
+					ResultSet rst = stmt.executeQuery("select id, foo, bar from testdata");
+					
+					if(rst.next())
+					{
+						foo=rst.getString(2);
+						bar=rst.getInt(3);
+					}
+					conn.close();
+				}
+			}
+		}
+		catch(Exception e) 
+		{
+			e.printStackTrace();
+		}
+	}
+
+	public String getFoo() { return foo; }
+
+	public int getBar() { return bar;}
+}
+</code></pre>