How to Solve Proxy Design Pattern Assignment Problem

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• Exercise Please Help Me To Solve This assignment Throught Proxy Design Pattern

** We’re going to build an O/RM (Object Relational Mapper). ORMs are tools responsible for mapping data between a relational database and an objectoriented model. There are many popular O/RMs out there such as Hibernate and Entity Framework. You can see a “super simplified” implementation of our imaginary ORM in the proxy package.

We use the DbContext class to read or write data to our database. The Demo class shows the typical workflow for using a DbContext

• Read an object from a database (dbContext.getProduct())
• Change the properties of the in-memory object (product.setName())
• Ask the dbContext to save the changes (dbContext.saveChanges())

If you run the code in the Demo class, you’ll only see a SELECT statement printed on the terminal. This simulates reading a product record from a database.

What is missing is the two UPDATE statements that should be generated when we save the changes. The reason this is happening is that our DbContext cannot keep track of the changed objects. So, when we call saveChanges(), nothing happens.

We can solve this problem using the proxy pattern. A proxy object looks like our target object (eg a Product object) but it adds some extra behavior to it.

For example, when we call the setName() method, the proxy notifies the DbContext that it is changed. DbContext provides a method for this: markAsChanged().

Use the proxy pattern to allow DbContext keep track of changed objects and persist them in a database.

NOTE: Some real-world O/RMs automatically generate these proxy objects based for you, so you don’t need to code them by hand.