- To build enterprise java applications
- simpler & light weight
- Spring 4 Key Features
- Inversion of Control
- Dependency injection
- Spring AOP
- Spring MVC
- Spring 5 new features
- Spring WebFlux
Spring Framework
- Goals
- Light weight java development with pojos
- Dependency injection for loose coupling
- Declarative programming with AOP(Aspect Oriented Programming)
- Minimize boiler plate java code
- Core Container
- Beans
- Core
- SpEL
- Context
- Infrastructure
- AOP
- Aspects
- Instrumentation
- Messaging
- Data access Layer
- JDBC
- ORM -> Object relation mapping
- Transactions
- OXM
- JMS
- Web Layer
- Servlet
- Websocket
- web
- portlet
- Test layer
- Unit
- integration
- Mock
- Only use what you need
- Spring Cloud, Spring Data
- Spring Batch, Spring Security
- Spring for Android, Spring for web flow
- Spring for Webservices, Spring for LDAP
- Spring Boot, Spring Social
Dev Env setup
- Tomcat8.5 + Eclipse
- Create Project
- Create a new folder lib in the project
- Download spring-framework-5.0.2-Release-dist.zip
- Add jar to the lib folder in the project
- Project properties -> java build path -> libraries -> classpath -> add jars -> select jars from lib folder
- Now referenced libraries should show the jars added
Spring Inversion of Control
- Design process of externalizing of construction and management of Objects
Spring Container
- Primary functions
- Create and manage Objects(Inversion of control) - Object Factory
- Inject Objects dependencies (Dependency management) -
- Configuration
- XML configuration (legacy)
- Java annotations(modern)
- Java source code(modern)
Spring development process
- Configure spring beans in config file
- applicationContext.xml -> define beans with bean ID & fully qualified class name
- Create Spring container
- This is generally known as ApplicationContext
- ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
- Retrieve beans from container
- Coach coach = context.getBean("myCoach",MyCoach.class);
- Dependency is same as helper objects
- Injection Types
- Constructor Injection
- Setter Injection
- Development process - constructor injection
- Create Dependency Interface & class that implements it
- Create Constructor in your class with parameter as Dependency Interface type
- Spring bean container/context
- Define Dendency bean
- Define regular bean and inject Dependency-bean as Constructor-arg
- Development process - setter injection
- Singleton
- for stateless beans
- prototype
- new object for each request
- for statefull bean
- request
- session
- global-session
Configuration with Annotations(XML Component scan)
- XML configuration can be too verbose for big projects
- Scanning for component classes
- Spring scans classes for special annotations
- They automatically register them in container
- Development process
- Enable component scanning in spring config file
- provide the base package for component scan in config file
- add @Component annotation to java class
- retrieve bean from spring container using context.getBean(<beanID>,Bean.class)
- autoWiring
- Spring looks for class that matches the property(class/interface) and injects it automatically.
- Injection types
- Construction
- @Autowired on top of constructor
- Setter
- Field
Java Configuration
- Development process
- Annotate java class with @ComponentScan & @Configuration
Spring MVC
- webpages to layout UI components
- Spring beans(Controller, services)
- Spring configuration(xm, annotations or java)
- Controller
- @Controller which inherits from Component
- @RequestMapping -> controller method
- Model
- It is container of application data
- Form Tags
AOP(Aspect Oriented Programming).
- It is module/code for cross cutting concenrs
- Technique based on concept of Aspect
- Aspect encapsulates cross-cutting logic
- It can be reused at multiple locations
- same aspect can be applied based on configuration
- Benefits
- Code lies in one class and not scattered
- code reuse and easy to change
- Business code is clean
- Configurable
- Use cases
- Logging, security, transactions
- audit logging
- exception handling
- API Management
- analytics/metrics
- Disadvantages
- Too many aspects - hard to follow app flow
- minor perf cost for aspect execution
- Terminology
- Aspect - It is module/code for cross cutting concerns
- Advice -What action is taken and when it should be applied
- BeforeAdvice..........
- Joint Point - When to apply code during program execution
- Pointcut-
- Weaving
- Connecting aspects to target objects to create an advised object
- types of weaving
- Compile time, load time or run time
- Frameworks
- SpringAOP, AspectJ
- SpringAOP advantages
- Simpler than SpectJ
- users Proxy pattern
- can migrate to AspectJ when using @Aspect annotation
- Spring AOP disadvantages
- supports only method-level joint points
- can apply aspects to beans created by Spring app context
- minor perf impact due to runtime aspect
Spring Security
- HTTP Basic Authentication
- builtin dialog from browser
- Default login form
- Spring provides default form
- Custom login form
Spring REST
- JSON
- Databinding
- process of converting json data into java pojo and vice versa
- spring uses jackson project behind the scene
- Json data sent to spring controller will be automatically converted to pojo
- java object returned from rest controller will be converted to JSON
- HTTP Request Message
- Request line
- Header variables
- Message Body
- REST Controller
- Exception Handler
- ResponseEntity is a wrapper on HTTP response object
Spring JDBC
- Spring simplifies the way we use java technologies
- JDBC
- Developers write lot of code which is repeated across classes in application
Connection, Statement, setParameters, - handle checked exceptions
- SpringJDBC
- Simplifies jdbc by creating JDBCTemplate
- it is combination of JDBC + Template design pattern
- Template carries common or boiler plate code and reduces amount of developers work
- JDBCTemplate depends on javax.sql.DataSource
- Steps to use JDBCTemplate
- config.xml
- create/configure bean dataSource for class DriverManagerDataSource providing driverClassName, url, user, pwd
- create/configure bean jdbcTemplate for class JDBCTemplate passing dataSource from above step
- jdbcTemplat.update(sql, <params to sql>);
- Query
- RowMapper
- Interace in Spring framework which needs to be implemented
- It maps resultset into Object of class that we create
- mapRow() to be implemented
-
- config.xml
Spring Boot
- Challenges addressed
- what maven arche type to be used
- what maven dependencies to be used
- configuration file
- what server to be used
- Spring boot
- easier to get started with Spring development
- minimize amount of manual configuration
- auto config based on props file and jar class path
- embedded server
- Overall- It is self-contained unit
- Spring initializer
- create starter project, select dependencies,
- https://start.spring.io/
- Creates Maven/gradle project
- Import project into IDE
- One can run the app from command line and IDE
- java -jar <jar name>
- Source code generated by spring boot initializer
- import org.springframework.boot.autoconfigure.SpringBootApplication
@SpringBootApplication -> This is composed of other annotations - The annotation composed of @EnableAutoConfiguration
@ComponentScan
@Configuration - SpringApplication.run
- Creates application context, register all beans
- starts embedded tomcat server
- application.properties for Custom properties
- Change default port
server.port=8181 - Properties defined here can be referenced in using
@Value("${<property name>}")
private String var1 - Spring boot dev tools
- Automatically restart application when code is changed
- simply add dependency spring-boot-devtools
- Spring boot Actuator
- Exposes end points to monitor application
- Easily get dev ops functionality out of box
- simply add dependency spring-boot-starter-actuator
- ../health
../info - Run from Command line
- java -jar <application.jar>
- mvnw:spring-boot:run
SpringBoot - Datasource configuration for Hibernate
- application.properties
- spring.datasource.url
- spring.datasource.username
- spring.datasource.password
- Spring boot will automatically create beans for DataSource and EntityManager
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