Spring

Spring

1. configuration

   • pom
     • build tag to change compiler (java version)
       • maven-compiler-plugin
         • configuration
           • java version
     • add spring dependency

2. xml configuration

   • application context
     • sort of Hash Map
     • can be a registry
     • multiple types of xml available
       • properties defined by its schema type
         • beans: allow us to defien multiple bean
     • namespaces
       • acts as a dictionary for the properties we can inject into a bean
     • need to create a context in the main method

3. beans

   • are essentially classes
     • replace keyword new
   • injection
     • setter
       • define the properties inside the bean in java code
       • in xml, bind the property with its bean
       • name based
     • can mix both
     • constructor
       • index based
       • need to define constructor for each situation
       • modify xml and bean
   • autowire
     • 4 ways
       • by type
         • as by name, match the bean property with the bean declared in xml, using the class type.
       • by name
         • uses set method, and tries to match the bean declared inside xml with the "setName method" inside the bean using the name
       • constructor
       • no
   • 5 possible scope for beans
     • Singleton
       • creates a single instance of a bean for each container
         • use @Scope("singleton" or ConfigurableBeanFactory.SCOPE_SINGLETON)
     • prototype
       • guarantee an unique instance per bean request
     • webScopes
       • Request
         • creates a bean per http request
       • Session
         • creates a single bean per live session
       • globalSession
         • creates a single bean per application

4. goals

   • separate configuration from logic (separation of concerns)
     • no need to recompile the whole project

5. Dependency Injection types

   • Annotation configuration
     • aplicationContext.xml
       • uses the beans schema
       • includes a component scanner
       • includes namespaces context (non version to keep compatibily)
     • Stereotype annotations
       • @Component
         • any POJO (meant to be a bean)
       • @Service
         • bussiness logic layer
           • the 3 define the name bean in parentesis
       • @Repository
         • Data Acess tier
       • semantically they are the same (service and repository extends component and dont add any feature, it`s about how you think of them and use them)
       • allow us to mark POJOS as Beans
     • Autowire
       • Can autowire at 3 places
         • member variables
           • should be avoided, makes the testing harder
         • constructor
           • the 3 approches uses the @autowired before the definition
         • setter
   • java configuration
     • uses java instead of xml
       • called AppConfig and define the beans?
     • there is no need to have an applicationContext
       • uses java instead of xml
         • called AppConfig and define the beans inside
         • uses the class level annotation @Configuration and @Bean
     • injection
       • setter injection
         • need to define a setter inside the class where beans will be injected, which will be called in "AppConfig"
       • construction injection
         • works as setter injection, but need a constructor instead
     • Autowire
       • is available, need to add a @ComponentScan at the top of AppConfig
       • there is no need to define beans in AppConfig (can be empty except for the Scanner)
         • Must use @Autowired just above the setter
         • and use stereotype tag for @Service or @Repository when defining a class

6. properties

   • abstact configuration and defined in one file
     • types
       • xml
         • need to
           • create a properties file
           • define its path in the application context.xml for the properties file
             • Define the property and its value inside the bean
           • create an attibute and its setter inside the bean
         • annotation
           • same steps just need to add @value in bean attibute, and annotation in application context
       • java config

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