Spring Tutorial

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Core

• IoC
• DI
• Beans
  • Step1: Creating beans
    • @Bean
    • @Component
  • Step2: Wiring (@Autowiring)
• Context
• SpEL
• IoC Container

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Stereotype Annotations

• @Component
  • @Controller
  • @Service
  • @Repository

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Bean Scope

1. Singleton
   • use case:
     • immutable beans
     • service layers
     • repository layers
   • points:
     • mutable singleton beans + multi thread environment => race condition
     • mutable singleton beans + multi thread environment + synchronization => NOT race condition
     • NOT best practice = bad practice => mutable singleton beans
2. Prototype
3. Request
4. Session
5. Application

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Aspect Oriented Programming (AOP)

• WWW
  • What -> Aspect
  • When -> Advice
  • Witch -> Pointcut
  • Join Point
  • Target Object

---

• Proxy Object of beans
  • Weaving
  • intercept
  • delegate

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• Advice:
  1. @Before
  2. @AfterReturning
  3. @AfterThrowing
  4. @After
  5. @Around

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Web App

• Web Server
  • Servlet Container (Http web server -> Http servlet object)
    • in: ServletRequest
    • out: ServletResponse
    • Apache Tomcat

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Dispatcher Servlet

• before:
  • /home => HomeServlet
  • /about => AboutServlet
  • /... => ...Servlet
• after:
  • /* => DispatcherServlet

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Web application

1. Approach 1: Spring MVC + Spring Core + Spring Boot + ...
2. Approach 2: Spring Core + Spring Boot + ...

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Spring Boot

1. SpringBoot Starters
   • spring-boot-starter-web
2. Autoconfiguration
   • convention-over-configuration
3. Actuator and DevTools
   • monitor app health, metrics, etc.
   • LiveReload Server

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Java Template Engine

• Thymeleaf
• Apache FreeMarker
• jte
• Jakarta Server Page (JSP)
• Jakarta Server Face (JSF)
  • PrimeFace
• ...

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Fetching Data

1. @PathVariable
   • www.jimsa.be/app/course <- Path variable
2. @RequestParam
   • www.jimsa.be/app?course=math&active=true <- Query Param
   • Form data

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Validation

• spring-boot-starter-validation:
  1. jakarta.validation.constraints.*
     • @Digits
     • @Email
     • @Max
     • @Min
     • @Not...
     • @Pattern
     • @Size
  2. org.hibernate.validator.constraints.*
     • @CreditCardNumber
     • @Length
     • Currency
     • @Range
     • @URL
     • @UniqueElements
     • @EAN
     • @ISBN

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Spring Web Scope

• Singleton
• Prototype

3. Request
   • @RequestScope
4. Session
   • @SessionScope
5. Application
   • ApplicationScope

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Security

• Thymeleaf Extras Springsecurity6
• CSRF

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• Encoding
  • unicode
  • base64
  • ascii
  • file formats
• Encryption
  • key
  • encryption
• Hashing
  • hash value
  • hashing function

---

• Password Encoder (using hash algorithms)
  • NoOpPasswordEncoder (No hashing stories in plain text)
  • StandardPasswordEncoder
  • Pbkdf2PasswordEncoder
  • BCryptPasswordEncoder (most commonly use)
  • SCryptPasswordEncoder

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Database

---

• H2
  • in-memory
  • schema.sql
  • data.sql
  • /h2-console
  • sa & ''

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1. JDBC
   • loading driver
   • management connections
   • statements
   • resultSets
   • ...

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2. Spring JDBC
   • spring-boot-starter-jdbc
   • JdbcTemplate

String lastName = this.jdbcTemplate.queryForObject(
        "select last_name from users where id = ?",
        String.class,
        123L
);

• NamedParameterJdbcTemplate

public int getCount(String firstName) {
    String sql = "select count(*) from users where first_name = :first_name";
    SqlParameterSource namedParameters = new SqlParameterSource("first_name", firstName);
    return this.namedParameterJdbcTemplate.queryForObject(
            sql,
            namedParameters,
            Integer.class
    );
}

• Using RowMapper
  • BeanPropertyRowMapper
• application.properties
  • spring.jdbc.template.*
  • spring.jdbc.template.max-rows=500

---

3. Spring Data Projects Link
   • Projects:
     • Spring Data JDBC
     • Spring Data JPA
     • Spring Data LDAP
     • Spring Data MongoDB
     • Spring Data Redis
     • Spring Data R2DBC
     • Spring Data REST
     • Spring Data for Apache Cassandra
     • Spring Data for Apache Geode
     • Spring Data Couchbase (community module)
     • Spring Data Elasticsearch (community module)
     • Spring Data Envers
     • Spring Data Neo4j (community module)
     • ...
   • Main modules
     • Spring Data Commons
       • Repository (marker interface)
         • CrudRepository
           • ListCrudRepository
         • PagingAndSortingRepository
           • ListPagingAndSortingRepository
     • Spring Data JPA
       • JpaRepository
   • Community modules

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Project

create a standalone Spring App which use two databases like MySql and PostgreSQL!

• dependency
• application.yml (application.properties)
  • spring.datasource.mysql/postgres.url/username/password/driver-class-name
  • jpa.hibernate.ddl-auto
  • jpa.mysql/postgres.properties.hibernate.dialect
• DataSource
• EntityManager
• TransactionManager
• LocalContainerEntityManagerFactoryBean
• EntityManagerFactoryBuilder
• PlatformTransactionManager
• JpaTransactionManager
• @Primary
• @Qualifier
• @PersistenceContext(unitName = "mysqlPU")
• private EntityManager mysqlEntityManager;
• @PersistenceContext(unitName = "postgresPU")
• private EntityManager postgresEntityManager;

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• JConnector
• JDBC
• JPA
• Spring Data
• Spring Data JPA
• Hibernate

---

• Query Methods in Spring Data JPA
  • introducer + By + criteria
• Auditing Support by Spring Data JPA
  • @CreatedDate
  • @CreatedBy
  • @LastModifiedDate
  • @LastModifiedBy

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Custom Validation

1. @interface...
2. impl ...
3. using ...

---

import jakarta.persistence.Transient;

@Transient
private String noDbOp; // Won't participate in DB operations like creating a table's column

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Database Relations

IMPORTANT : Link

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Sorting

1. static
   • findByOrderByNameDesc()
2. dynamic
   • Sort.by("name").descending().and(Sort.by("age"))

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Paging

import org.springframework.data.domain.Page;
import org.springframework.data.domain.PageRequest;
import org.springframework.data.domain.Pageable;
import org.springframework.data.domain.Sort;

Pageable pageable = PageRequest.of(
        0,
        10,
        Sort.by("name").descending()
);
Page<Person> personPage = repo.findByName(name, pageable);

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Custom Query with JPA

1. @Query
   • JPQL
   • Native SQL query (nativeQuery=true)
2. @NamedQuery
3. @NamedNativeQuery
   • Spring Data JPA doesn’t support dynamic sorting for native queries
   • Example:
     • Link 1
     • Link 2

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• Update, Delete, Insert
  • @Transactional
  • @Modifying

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Rest APIs

• @RestController = @Controller + @ResponseBody
• @RestControllerAdvice
• ReponseEntity<T>
• RequestEntity<T> -> getBody()
• @RequestHeader
• @RequestBody

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Cross-origin resource sharing (CORS)

• protocol

• domain

• port

• @CrossOrigin("*")

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Jackson JSON

link

import com.fasterxml.jackson.annotation.JsonIgnore;
import com.fasterxml.jackson.annotation.JsonProperty;

import java.time.LocalDateTime;

@JsonProperty("first_name")
private String firstName;

@JsonIgnore
private LocalDateTime createdAt;

---

Requests:

curl --location 'http://localhost:8090/springapp/api/person'

curl --location --request GET 'http://localhost:8090/springapp/api/person/byRequestBodyAnnotation' \
--header 'Content-Type: application/json' \
--data '{
    "first_name": "jimsa2",
    "last_name": "salehi2"
}'

curl --location 'http://localhost:8090/springapp/api/person' \
--header 'invocationFrom: mobile' \
--header 'Content-Type: application/json' \
--data '{
    "first_name": "jimsa3",
    "last_name": "salehi3"
}'

curl --location --request DELETE 'http://localhost:8090/springapp/api/person' \
--header 'Content-Type: application/json' \
--data '{
    "first_name": "jimsa4",
    "last_name": "salehi4"
}'

curl --location --request PATCH 'http://localhost:8090/springapp/api/person' \
--header 'Content-Type: application/json' \
--data '{
    "first_name": "jimsa6"
}'

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Rest APIs consuming

IMPORTANT : Link

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Spring Data Rest & HAL Explorer

• link1
• link2
• link3

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Logging

• AOP -> MyLogAspect

Libs:

• Java util logging
• Log4J2
• SLF4J
• Logback
  • The default logging framework
  • The default logging destination is the console
    • System.out
    • System.err
  • Link

Levels:

• fatal
• error
• warn
• info
• debug
• trace

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Configuration

• @Value
• environment.getProperty("...")
• -> default into application.properties

---

Profile

• application_prod.properties
• application_dev.properties

spring.profiles.active

• @Profile("!dev")

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Spring Actuator and Spring Boot Admin

• http://localhost:8090/springapp/actuator/
• management.endpoints.web.exposure.include=*

• Spring Boot Admin
  • client
    • link
  • server
    • link
  • hibernate-micrometer
    • link

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Heap Dumps

1. JDK Tools
   • jmap
   • jcmd
   • JVisualVM
2. Automatically
   • java -XX:+HeapDumpOnOutOfMemoryError
   • java -XX:+HeapDumpOnOutOfMemoryError -XX:HeapDumpPath=<file-or-dir-path>
3. JMX
   • JConsole
   • Programmatic Way

public static void dumpHeap(String filePath, boolean live) throws IOException {
    MBeanServer server = ManagementFactory.getPlatformMBeanServer();
    HotSpotDiagnosticMXBean mxBean = ManagementFactory.newPlatformMXBeanProxy(
      server, "com.sun.management:type=HotSpotDiagnostic", HotSpotDiagnosticMXBean.class);
    mxBean.dumpHeap(filePath, live);
}