global db connection settings in struts2

[Rajani Panchumarthy]

Hi,

I am setting postgresql db connection parameters like protocol, url, username in action class of struts2 framework.
How can I declare these connection params globally within the application.
Thanks in advance.

[Balagopal Kannampallil]

First of all you can create an interface say ConnectionAware which will be implemented by classes which needs the connection obect

   
public interface ConnectionAware {
	public void setConnection(Connection connection);

}

The implementation class will look like this

   
public class SampleAction extends ActionSupport implements ConnectionAware {

	Connection myConn;

	@Override
	public String execute() throws Exception {
           //your execution code
	}

	public void setConnection(Connection connection) {
		myConn = connection;
		
	}

}

Then create your own interceptor to which creates the actual connection with the parameters you have set globally and inject the connection into the required classes which implement ConnectionAware interface.

public class ResourceInterceptor implements Interceptor {
	 
	Connection connection;
	
	//values will be defined in the struts.xml
	private String driverClass;
	private String connectionURL;
	private String username;
	private String password;
	


	public void init() {
		try {
			Class.forName(this.getDriverClass());
			connection = DriverManager.getConnection(this.getConnectionURL(),
                                                                    this.getUsername(),this.getPassword());
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		} catch (SQLException e) {
			e.printStackTrace();
		}

	}

	public String intercept(ActionInvocation invocation) throws Exception {
		if (invocation.getAction() instanceof ConnectionAware) {
			((ConnectionAware)invocation.getAction()).setConnection(connection);
			System.out.println("Connection Successfuly Injected.");
		}
		return invocation.invoke();
	}
	
	public void destroy() {
		try {
			connection.close();
		} catch (SQLException e) {
			e.printStackTrace();
		}
	}


	public String getDriverClass() {
		return driverClass;
	}

	public void setDriverClass(String driverClass) {
		this.driverClass = driverClass;
	}

	public String getConnectionURL() {
		return connectionURL;
	}

	public void setConnectionURL(String connectionURL) {
		this.connectionURL = connectionURL;
	}

	public String getUsername() {
		return username;
	}

	public void setUsername(String username) {
		this.username = username;
	}

	public String getPassword() {
		return password;
	}

	public void setPassword(String password) {
		this.password = password;
	}
}

Finally after the creation of your interceptor class, you can include this interceptor in your interceptors tag inside your struts.xml

	<interceptors>
			<interceptor name="resourceInterceptor" class="ResourceInterceptor" />
	</interceptors>

Now in the action tag you can include the interceptor-ref to point to the newly created interceptor.

      
            <!-- Binding the intereceptor to the action -->
        	<interceptor-ref name="resourceInterceptor">        	
        		<param name="driverClass">sun.jdbc.odbc.JdbcOdbcDriver</param>
        		<param name="connectionURL">jdbc:odbc:ExcelData</param>
        		<param name="username">username</param>
        		<param name="password">password</param>
        	</interceptor-ref>   

Here I have used sun.jdbc.odbc.JdbcOdbcDriver as driverClass and jdbc: odbc:ExcelData as connectionURL

[Rajani Panchumarthy]

Hello,
Thank you for an elaborate answer.
I am able to make the connection to the db.
However, when I try to submit the form, null values are being inserted into db, i.e., the form parameters are found to be null in the execute method of the action class.
struts.xml file is as follows:
<action name="add" class="AddUser">
<result name="error">/jsppages/addUser.jsp</result>
<result name="input">/jsppages/addUser.jsp</result>
<result>/jsppages/regSuccess.jsp</result>
<interceptor-ref name="resourceInterceptor">
<param name="driverClass">org.postgresql.Driver</param>
<param name="connectionURL">jdbc:postgresql:postgres</param>
<param name="username">postgres</param>
<param name="password">post123</param>
</interceptor-ref>
</action>

the form where the user details are entered invokes the above add action.In this action class, I am getting the user details using getter method and trying to insert into db.But the values that the getter method is returned as null.

Is this behaviour due to the interceptor that is being called as soon as the add.action is invoked??
Could you please let me know if there is anything missing in struts.xml file??

[Balagopal Kannampallil]

Just put interceptor-ref before the result....conventions

    
<action name="add" class="AddUser">
<interceptor-ref name="resourceInterceptor">
<param name="driverClass">org.postgresql.Driver</param>
<param name="connectionURL">jdbc:postgresql:postgres</param>
<param name="username">postgres</param>
<param name="password">post123</param>
</interceptor-ref>
<result name="error">/jsppages/addUser.jsp</result>
<result name="input">/jsppages/addUser.jsp</result>
<result>/jsppages/regSuccess.jsp</result>
</action> 

The value which you populate inside the input method, will not be obtained by default in the execute method. For example if you have a ArrayList namely myList as the form/action attribute and you populate some values into myList in the input method and you want to access them in the execute method also, you will have to
1. After putting the values into myList, put myList object into session from the input method.
2. Get myList object back from session in the execute method and set it to the myList using its setter method.

There is also another option. You can make myList static. I am saying this just for study purpose (Warning: Never try to implement this on a multi-user web application).

[Rajani Panchumarthy]

Thanks you.It worked.