.NET/Java PDF, Tiff, Barcode SDK Library

As you descend into the details of moving your interdependent lists into a control of their own, more issues will arise. What if someone uses two instances of your control on a page of her own You d have duplicate populateListB methods injected into the page, which would not make the browser happy. What if you wanted the static parts of your code in their own file (.js) How can you be sure to inject this only once The Page object has a number of types and methods designed to help with just such problems.

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Single Proxy Connection Carrying Three Sessions midtier Connection db_clerk1 Session db_clerk1 Session db_manager1 Session

Parameters let values (internal)

Figure 15-4 A proxy connection carrying three sessions We will use our sample application to demonstrate the proxy authentication concept We first create a database account to connect to the database on behalf of end users This account is separate from the end user database accounts (db_manager1 and db_clerk1 in our application) and is called midtier in our example: admin@ORA10G> create user midtier identified by midtier; User created The account midtier is the proxy account that connects on behalf of all end users to the database from the middle-tier application hosted on an application server As per the principle of least privilege, we should give it the minimum privilege to get the job done That privilege is the create session privilege, which allows it to connect to the database: admin@ORA10G> grant create session to midtier; Grant succeeded.

Table 19-2. Conventions Associated with Public Constructs in .NET Frameworks and Author-Recommended Extensions for F# Constructs (Continued)

Version 1.x of the Framework has a handful of methods hanging off of the Page object to help with client-side scripting. One of these, for example, is RegisterClientScriptBlock. This handy method accepts two strings. The first one names the script block; the second is the actual script you want to inject into the page. You use this from controls to inject script into the page while avoiding duplicate script blocks. If more than one instance of a control attempts to inject the same script block, the runtime is smart enough to inject it only once. From the previous example, you could pull the populateListB method out into a file named Interdepends.js. From the implementation of the interdependent lists control, you could add a line of code to include it: this.RegisterClientScriptBlock( "Interdepends", "<script language='JavaScript1.2' src='/Interdepends.js'>"); This is a two-fold improvement over the previous example. It gets the script out into its own file (for easier maintenance and versioning), and it guarantees that the block will be included in the page only once.

To enable the end user account, db_manager1, to be able to be proxied by the account midtier, we need to alter the db_manager1 account as follows: admin@ORA10G> -- allow connecting through proxy account admin@ORA10G> alter user db_manager1 grant connect through midtier with role manager_role, clerk_role; User altered The preceding alter statement in effect says that the user midtier can connect with the privileges of db_manager1 without supplying the db_manager1 password, and during this connection it can enable only the roles manager_role and clerk_role This means that when the application is proxying for db_manager1 via the account midtier, only two specific roles can be enabled: manager_role and clerk_role Restricting the roles in this manner ensures that the application can enable only the roles with the minimum privileges to do its job.

let values (external)

We issue the same alter statement to the user db_clerk1; however, this time we allow only clerk_role to be enabled during the proxy connection admin@ORA10G> alter user db_clerk1 grant connect through midtier with role clerk_role; User altered..

All of the RegisterXYZ methods (see Table 4-2) have been deprecated in version 2.0 of the Framework. Instead, the page object now carries an instance of the new ClientScriptManager type, named ClientScript. This centralizes the functionality for managing scripts; you no longer have a handful of random methods hanging off the page object. Table 4-2. Methods of the Page Object That Are Officially Depreacted in Version 2.0

let-bound values are often public when following traditional functional design patterns. However, generally use PascalCase when the identifier can be used from other .NET languages. Boolean properties generally use Is and Can and should be affirmative, as in IsEndOfFile, not IsNotEndOfFile.