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BAEL-4135 - When are static variables initialized? (#9607) 

* Hexagonal Architecture in Java

A quick and practical example of Hexagonal Architecture in Java

* Fixed code formatting issues

* When are static variables initialized

Sample class and test class.

* Revert "When are static variables initialized"

This reverts commit c781923093ccc88bc269bea276653169065cb17b.

* Revert "Revert "When are static variables initialized""

This reverts commit 2bffdf401d4e7dc2cefd7eb16357b2d51271edad.

* New java module for static variable

Created a new core-java-lang-3 module for static variables.

* PR review changes: Added more scenarios to the static variable test

Covered the following cases:
1. Variable initialization in a static block
2. Variable initialization in a static nested class
This commit is contained in:
SauDev 2020-07-17 11:43:25 +05:30 committed by GitHub
parent 60ef1c8551
commit dc06936a5d
16 changed files with 449 additions and 1 deletions
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23
core-java-modules/core-java-lang-3/src/main/java/com/baeldung/staticvariables/StaticVariableDemo.java Normal file
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package com.baeldung.staticvariables;
public class StaticVariableDemo {
public static int i;
public static int j = 20;
public static int z;
static {
z = 30;
a = 40;
}
public static int a = 50;
public static final int b = 100;
public StaticVariableDemo() {
}
static class Nested {
public static String nestedClassStaticVariable = "test";
}
}

113
core-java-modules/core-java-lang-3/src/test/java/com/baeldung/staticvariables/StaticVariableUnitTest.java Normal file
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package com.baeldung.staticvariables;
import static org.assertj.core.api.Assertions.assertThat;
import java.lang.reflect.Field;
import org.junit.jupiter.api.Test;
public class StaticVariableUnitTest {
@Test
public void initializeStaticVariable_checkAssignedValues() {
try {
Class<?> staticVariableDemo = this.getClass()
.getClassLoader()
.loadClass("com.baeldung.staticvariables.StaticVariableDemo");
Field field1 = staticVariableDemo.getField("i");
assertThat(field1.getInt(staticVariableDemo)).isEqualTo(0);
Field field2 = staticVariableDemo.getField("j");
assertThat(field2.getInt(staticVariableDemo)).isEqualTo(20);
} catch (ClassNotFoundException | NoSuchFieldException | SecurityException e) {
e.printStackTrace();
} catch (IllegalArgumentException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
}
}
@Test
public void initializeStaticVariable_checkStaticBlock() {
try {
Class<?> staticVariableDemo = this.getClass()
.getClassLoader()
.loadClass("com.baeldung.staticvariables.StaticVariableDemo");
Field field1 = staticVariableDemo.getField("z");
assertThat(field1.getInt(staticVariableDemo)).isEqualTo(30);
Field field2 = staticVariableDemo.getField("a");
assertThat(field2.getInt(staticVariableDemo)).isEqualTo(50);
} catch (ClassNotFoundException | NoSuchFieldException | SecurityException e) {
e.printStackTrace();
} catch (IllegalArgumentException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
}
}
@Test
public void initializeStaticVariable_checkFinalValues() {
try {
Class<?> staticVariableDemo = this.getClass()
.getClassLoader()
.loadClass("com.baeldung.staticvariables.StaticVariableDemo");
Field field1 = staticVariableDemo.getField("b");
assertThat(field1.getInt(staticVariableDemo)).isEqualTo(100);
} catch (ClassNotFoundException | NoSuchFieldException | SecurityException e) {
e.printStackTrace();
} catch (IllegalArgumentException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
}
}
@Test
public void initializeStaticVariable_checkInnerClassValues() {
try {
Class<?> staticVariableDemo = this.getClass()
.getClassLoader()
.loadClass("com.baeldung.staticvariables.StaticVariableDemo");
Class<?>[] nestedClasses = staticVariableDemo.getClasses();
for (Class<?> nestedClass : nestedClasses) {
if (nestedClass.getName()
.equals("Nested")) {
Field field1 = nestedClass.getField("nestedClassStaticVariable");
assertThat(field1.get(nestedClass)).isEqualTo("test");
}
}
} catch (ClassNotFoundException | NoSuchFieldException | SecurityException e) {
e.printStackTrace();
} catch (IllegalArgumentException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
}
}
}

59
patterns/hexagonal-architecture/pom.xml Normal file
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<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.3.0.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.baeldung</groupId>
<artifactId>hexagonal-architecture</artifactId>
<version>1.0</version>
<name>hexagonal-architecture</name>
<description>Project for hexagonal architecture in java</description>
<properties>
<java.version>1.8</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-mongodb</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
<exclusions>
<exclusion>
<groupId>org.junit.vintage</groupId>
<artifactId>junit-vintage-engine</artifactId>
</exclusion>
</exclusions>
</dependency>
<dependency>
<groupId>org.mockito</groupId>
<artifactId>mockito-core</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>

13
patterns/hexagonal-architecture/src/main/java/com/baeldung/pattern/hexagonal/HexArchApplicationDemo.java Normal file
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package com.baeldung.pattern.hexagonal;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class HexArchApplicationDemo {
public static void main(String[] args) {
SpringApplication.run(HexArchApplicationDemo.class, args);
}
}

15
patterns/hexagonal-architecture/src/main/java/com/baeldung/pattern/hexagonal/config/AppConfig.java Normal file
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package com.baeldung.pattern.hexagonal.config;
import com.baeldung.pattern.hexagonal.domain.services.EmployeeService;
import com.baeldung.pattern.hexagonal.domain.services.EmployeeServiceImpl;
import com.baeldung.pattern.hexagonal.persistence.EmployeeRepository;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
@Configuration
public class AppConfig {
@Bean
public EmployeeService getEmployeeService(EmployeeRepository employeeRepository) {
return new EmployeeServiceImpl(employeeRepository);
}
}

10
patterns/hexagonal-architecture/src/main/java/com/baeldung/pattern/hexagonal/config/MongoConfig.java Normal file
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package com.baeldung.pattern.hexagonal.config;
import com.baeldung.pattern.hexagonal.persistence.MongoRepoEx;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.mongodb.repository.config.EnableMongoRepositories;
@Configuration
@EnableMongoRepositories(basePackageClasses = MongoRepoEx.class)
public class MongoConfig {
}

25
patterns/hexagonal-architecture/src/main/java/com/baeldung/pattern/hexagonal/controller/EmployeeController.java Normal file
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package com.baeldung.pattern.hexagonal.controller;
import com.baeldung.pattern.hexagonal.domain.model.Employee;
import com.baeldung.pattern.hexagonal.domain.services.EmployeeService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.MediaType;
import org.springframework.web.bind.annotation.*;
@RestController
@RequestMapping("/employees")
public class EmployeeController {
@Autowired
EmployeeService employeeService;
@PostMapping(produces = MediaType.APPLICATION_JSON_VALUE, consumes = MediaType.APPLICATION_JSON_VALUE)
@ResponseBody
public Employee addEmployee(@RequestBody Employee employee) {
return employeeService.addEmployee(employee);
}
@GetMapping(path = "/{employeeId}")
public Employee getEmployee(@PathVariable("employeeId") String employeeId) {
return employeeService.getEmployee(employeeId);
}
}

51
patterns/hexagonal-architecture/src/main/java/com/baeldung/pattern/hexagonal/domain/model/Employee.java Normal file
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package com.baeldung.pattern.hexagonal.domain.model;
import org.springframework.data.annotation.Id;
import java.util.Objects;
public class Employee {
@Id
private String empId;
private String empName;
private String empJobTitle;
public String getEmpId() {
return empId;
}
public void setEmpId(String empId) {
this.empId = empId;
}
public String getEmpName() {
return empName;
}
public void setEmpName(String empName) {
this.empName = empName;
}
public String getEmpJobTitle() {
return empJobTitle;
}
public void setEmpJobTitle(String empJobTitle) {
this.empJobTitle = empJobTitle;
}
@Override
public boolean equals(Object o) {
if (this == o)
return true;
if (o == null || getClass() != o.getClass())
return false;
Employee employee = (Employee) o;
return empId.equals(employee.empId);
}
@Override
public int hashCode() {
return Objects.hash(empId);
}
}

10
patterns/hexagonal-architecture/src/main/java/com/baeldung/pattern/hexagonal/domain/services/EmployeeService.java Normal file
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package com.baeldung.pattern.hexagonal.domain.services;
import com.baeldung.pattern.hexagonal.domain.model.Employee;
public interface EmployeeService {
Employee addEmployee(Employee employee);
Employee getEmployee(String employeeId);
}

34
patterns/hexagonal-architecture/src/main/java/com/baeldung/pattern/hexagonal/domain/services/EmployeeServiceImpl.java Normal file
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package com.baeldung.pattern.hexagonal.domain.services;
import com.baeldung.pattern.hexagonal.domain.model.Employee;
import com.baeldung.pattern.hexagonal.persistence.EmployeeRepository;
import org.springframework.beans.factory.annotation.Autowired;
import java.util.Optional;
public class EmployeeServiceImpl implements EmployeeService {
private EmployeeRepository employeeRepository;
@Autowired
public EmployeeServiceImpl(EmployeeRepository employeeRepository) {
this.employeeRepository = employeeRepository;
}
@Override
public Employee addEmployee(Employee employee) {
return employeeRepository.add(employee);
}
@Override
public Employee getEmployee(String employeeId) {
Optional<Employee> employee = employeeRepository.findById(employeeId);
if (employee.isPresent()) {
return employee.get();
} else {
// throw
}
return null;
}
}

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patterns/hexagonal-architecture/src/main/java/com/baeldung/pattern/hexagonal/persistence/EmployeeRepository.java Normal file
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package com.baeldung.pattern.hexagonal.persistence;
import com.baeldung.pattern.hexagonal.domain.model.Employee;
import org.springframework.stereotype.Repository;
import java.util.Optional;
@Repository
public interface EmployeeRepository {
Employee add(Employee employee);
Optional<Employee> findById(String id);
}

24
patterns/hexagonal-architecture/src/main/java/com/baeldung/pattern/hexagonal/persistence/MongoDBRepository.java Normal file
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package com.baeldung.pattern.hexagonal.persistence;
import com.baeldung.pattern.hexagonal.domain.model.Employee;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Repository;
import java.util.Optional;
@Repository
public class MongoDBRepository implements EmployeeRepository {
@Autowired
MongoRepoEx mongoRepository;
@Override
public Employee add(Employee employee) {
return mongoRepository.insert(employee);
}
@Override
public Optional<Employee> findById(String id) {
return mongoRepository.findById(id);
}
}

9
patterns/hexagonal-architecture/src/main/java/com/baeldung/pattern/hexagonal/persistence/MongoRepoEx.java Normal file
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package com.baeldung.pattern.hexagonal.persistence;
import com.baeldung.pattern.hexagonal.domain.model.Employee;
import org.springframework.data.mongodb.repository.MongoRepository;
import org.springframework.stereotype.Repository;
@Repository
public interface MongoRepoEx extends MongoRepository<Employee, String> {
}

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patterns/hexagonal-architecture/src/main/resources/application.properties Normal file
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46
patterns/hexagonal-architecture/src/test/java/com/baeldung/pattern/hexagonal/domain/services/EmployeeServiceImplTest.java Normal file
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package com.baeldung.pattern.hexagonal.domain.services;
import com.baeldung.pattern.hexagonal.domain.model.Employee;
import com.baeldung.pattern.hexagonal.persistence.EmployeeRepository;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
import java.util.Optional;
import static org.junit.jupiter.api.Assertions.*;
import static org.mockito.ArgumentMatchers.any;
import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.when;
class EmployeeServiceImplTest {
private EmployeeRepository employeeRepository;
private EmployeeService testService;
private Employee testModel;
@BeforeEach
void setUp() {
employeeRepository = mock(EmployeeRepository.class);
testService = new EmployeeServiceImpl(employeeRepository);
testModel = new Employee();
testModel.setEmpId("2000");
testModel.setEmpName("Test user 1");
testModel.setEmpJobTitle("Software engineer");
}
@Test
void addEmployee() {
when(employeeRepository.add(any(Employee.class))).thenReturn(testModel);
Employee testResponse = testService.addEmployee(testModel);
assertEquals(testModel, testResponse);
}
@Test
void getEmployee() {
when(employeeRepository.findById("2000")).thenReturn(Optional.of(testModel));
Employee testResponse = testService.getEmployee("2000");
assertEquals(testModel, testResponse);
}
}