A servlet class is injected with a JDBC data source. After injection has occurred, the servlet needs to create a cache out of some of the data in the database, so as to improve responsiveness. Which…

The correct answer is A. Servlet.init() D. A method annotated with @PostConstruct. A: Because the Servlet init() method is invoked when the servlet instance is loaded, it is the perfect location to carry out expensive operations that need only be performed during initialization. By definition, the init() method is thread-safe. The results of operations in the…

Servlets

Question

A servlet class is injected with a JDBC data source. After injection has occurred, the servlet needs to create a cache out of some of the data in the database, so as to improve responsiveness. Which two methods can host the cache creation code? (Choose two)

Options

AServlet.init()
BServlet.destroy()
CA method annotated with @Init
DA method annotated with @PostConstruct
EA method annotated with @PreDestroy
FA method annotated with @Resource

How the community answered

(47 responses)

A
81% (38)
B
2% (1)
C
9% (4)
E
6% (3)
F
2% (1)

Explanation

A: Because the Servlet init() method is invoked when the servlet instance is loaded, it is the perfect location to carry out expensive operations that need only be performed during initialization. By definition, the init() method is thread-safe. The results of operations in the HttpServlet.init() method can be cached safely in servlet instance variables, which become read- only in the servlet service method. private void init() { cached = (Cached) ctx.lookup(EJB_PATH + Cached.class.getSimpleName());

Topics

#@PostConstruct#dependency injection#servlet lifecycle#JDBC DataSource

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