In previous chapters, we have seen how Spring works in the backend to access data for the application. We also saw how the Spring JDBC Module provides the JdbcTemplate helper class for database access. Spring provides support for integration with ORM solutions such as Hibernate, JPA, JDO, and so on, and manages transactions across application. Now, in this chapter, we will see how Spring provides caching support to improve application performance.
Do you ever face a volley of questions from your wife when you return home very late in the night from your office? Yes, I know it is very irritating to answer so many questions when you are tired and exhausted. It is even more irritating when you're asked the same questions over and over again..
Some questions can be answered with a Yes or No, but for some questions, you have to explain in detail. Consider what will happen if you are asked another lengthy question again after some time! Similarly, there are some stateless components in an application, where the components have been designed in such a way that they ask the same questions over and over again to complete each task individually. Similar to some questions asked by your wife, some questions in the system take a while to fetch the appropriate data--it may have some major complex logic behind it, or maybe, it has to fetch data from the database, or call a remote service.
If we know that the answer of a question is not likely to change frequently, we can remember the answer to that question for later when it is asked again by the same system. It doesn't make sense to go through the same channel to fetch it again, as it will impact your application's performance, and will be a wasteful use of your resources. In an enterprise application, caching is a way to store those frequently needed answers so that we fetch from the cache instead of going through the proper channel to get the answer for the same question over and over again. In this chapter, we will discuss Spring's Cache Abstraction feature, and how Spring declaratively supports caching implementation. It will cover the following points:
- What is a cache?
- Where do we do this caching?
- Understanding the cache abstraction
- Enabling caching via the Proxy pattern
- Declarative Annotation-based caching
- Declarative XML-based caching
- Configuring the cache storage
- Implementing custom cache annotations
- Caching best practices
Let's begin.