AOP and Proxy: Behind the scene of Spring Data

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1. AOP and Proxy: Behind the scene of Spring Mitsunori Komatsu
2. Query Methods in Spring Data JDBC is very useful! Great! But how does it work? SELECT * FROM users WHERE name LIKE ‘%${name}%’ ORDER BY id DESC LIMIT 3
3. Technologies - Reflection - To find annotated classes/variables/methods - Out of the scope of this presentation
4. Technologies - Proxy The automatically assigned variable is Proxy…?
5. What is Proxy in Spring? <<interface>> org.springframework.aop.framework.AopProxy org.springframework.aop.framework. JdkDynamicAopProxy - Internally uses java.lang.reflect.Proxy org.springframework.aop.framework. CglibAopProxy - Internally uses CGLIB (byte code gen library) What is AOP…?
6. - Aspect-oriented programming (AOP) is a programming paradigm that aims to increase modularity by allowing the separation of cross-cutting concerns - This allows behaviors that are not central to the business logic to be added to a program without cluttering the code core to the functionality - For instance, - Logging - Retry - Authorization Retry AccountServi ce.transfer OrderService .placeOrder StorageServi ce.addItem What is AOP? Logging before-state Authorization Logging before-state Business logics AOP actions These explanations are copied from Wikipedia, right?
7. Aspect The terminology of AOP Join point: account.getId() Method calls, field accesses and object instantiations. Spring AOP supports only Method calls Pointcut Predicates that match join points Program execution Advice is associated with a pointcut expression and runs at any join point matched by the pointcut Join point: user.age = 42 Join point: group.setName(x) Join point: item.setPrice(p) In the following example, - MyAspect is Aspect - @Before(“execution(...)”) is Pointcut - logValues() is Advice @Aspect public class MyAspect { @Before("execution(* set*(..))") public void logValues() { ... } } Advice An action taken by an aspect at a particular join point. Different types of advice include "around", "before", and "after" advice This Pointcut means - The execution of any method with a name that begins with set OK. But how Proxy is used in AOP…?
8. AOP Proxy : method call via object reference https://docs.spring.io/spring-framework/docs/current/reference/html/core.html
9. AOP Proxy : method call via Proxy https://docs.spring.io/spring-framework/docs/current/reference/html/core.html We can inject Advice to a Proxy. It seems useful for AOP!
10. AOP in Spring AOP engines in Spring Spring AOP Supported Join Points: - Method execution AspectJ Supported Join Points: - Method execution - Field access - Object instantiation - etc. CGLIB based Proxy - Use CGLIB (byte code generation library) - Support interface/class JDK based Proxy - Use java.lang.reflect.Proxy - Support only interface AOP interfaces in Spring AspectJ style - Annotation based - Compatible with AspectJ class ProxyFactory - Create a proxy instance programmatically
11. Example: Duration tracing using AspectJ style Aspect Pointcut Advice This service instance is a proxy in fact
12. Example: Query Method-ish Proxy using ProxyFactory This class is a delegate for other method calls Advice Ugly manual Pointcut… Calculate a return value