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[BAEL-13505] Move articles out of core-java part 1

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Sjmillington
2019-09-05 17:44:52 +01:00
parent 434bfc980e
commit 3e155818d5
36 changed files with 28 additions and 0 deletions
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1
core-java-modules/core-java-reflection/README.MD
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## Relevant Articles
- [Void Type in Java](https://www.baeldung.com/java-void-type)
- [Retrieve Fields from a Java Class Using Reflection](https://www.baeldung.com/java-reflection-class-fields)

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core-java-modules/core-java-reflection/src/main/java/com/baeldung/reflection/BaeldungReflectionUtils.java Normal file
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package com.baeldung.reflection;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.beans.Introspector;
import java.beans.PropertyDescriptor;
import java.lang.reflect.Method;
import java.util.Arrays;
import java.util.List;
import java.util.function.Predicate;
import java.util.stream.Collectors;
class BaeldungReflectionUtils {
private static final Logger LOG = LoggerFactory.getLogger(BaeldungReflectionUtils.class);
static List<String> getNullPropertiesList(Customer customer) throws Exception {
PropertyDescriptor[] propDescArr = Introspector.getBeanInfo(Customer.class, Object.class).getPropertyDescriptors();
return Arrays.stream(propDescArr)
.filter(nulls(customer))
.map(PropertyDescriptor::getName)
.collect(Collectors.toList());
}
private static Predicate<PropertyDescriptor> nulls(Customer customer) {
return pd -> {
boolean result = false;
try {
Method getterMethod = pd.getReadMethod();
result = (getterMethod != null && getterMethod.invoke(customer) == null);
} catch (Exception e) {
LOG.error("error invoking getter method");
}
return result;
};
}
}

56
core-java-modules/core-java-reflection/src/main/java/com/baeldung/reflection/Customer.java Normal file
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package com.baeldung.reflection;
public class Customer {
private Integer id;
private String name;
private String emailId;
private Long phoneNumber;
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getEmailId() {
return emailId;
}
public void setEmailId(String emailId) {
this.emailId = emailId;
}
@Override
public String toString() {
return "Customer [id=" + id + ", name=" + name + ", emailId=" + emailId + ", phoneNumber=" +
phoneNumber + "]";
}
Customer(Integer id, String name, String emailId, Long phoneNumber) {
super();
this.id = id;
this.name = name;
this.emailId = emailId;
this.phoneNumber = phoneNumber;
}
public Long getPhoneNumber() {
return phoneNumber;
}
public void setPhoneNumber(Long phoneNumber) {
this.phoneNumber = phoneNumber;
}
}

7
core-java-modules/core-java-reflection/src/main/java/com/baeldung/reflection/Employee.java Normal file
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package com.baeldung.reflection;
public class Employee extends Person {
public int employeeId;
}

7
core-java-modules/core-java-reflection/src/main/java/com/baeldung/reflection/MonthEmployee.java Normal file
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package com.baeldung.reflection;
public class MonthEmployee extends Employee {
protected double reward;
}

8
core-java-modules/core-java-reflection/src/main/java/com/baeldung/reflection/Person.java Normal file
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package com.baeldung.reflection;
public class Person {
protected String lastName;
private String firstName;
}

24
core-java-modules/core-java-reflection/src/test/java/com/baeldung/reflection/BaeldungReflectionUtilsUnitTest.java Normal file
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package com.baeldung.reflection;
import org.junit.Test;
import java.util.Arrays;
import java.util.List;
import static org.junit.Assert.assertTrue;
public class BaeldungReflectionUtilsUnitTest {
@Test
public void givenCustomer_whenAFieldIsNull_thenFieldNameInResult() throws Exception {
Customer customer = new Customer(1, "Himanshu", null, null);
List<String> result = BaeldungReflectionUtils.getNullPropertiesList(customer);
List<String> expectedFieldNames = Arrays.asList("emailId", "phoneNumber");
assertTrue(result.size() == expectedFieldNames.size());
assertTrue(result.containsAll(expectedFieldNames));
}
}

150
core-java-modules/core-java-reflection/src/test/java/com/baeldung/reflection/PersonAndEmployeeReflectionUnitTest.java Normal file
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package com.baeldung.reflection;
import org.junit.Test;
import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;
import static org.junit.Assert.*;
public class PersonAndEmployeeReflectionUnitTest {
// Fields names
private static final String LAST_NAME_FIELD = "lastName";
private static final String FIRST_NAME_FIELD = "firstName";
private static final String EMPLOYEE_ID_FIELD = "employeeId";
private static final String MONTH_EMPLOYEE_REWARD_FIELD = "reward";
@Test
public void givenPersonClass_whenGetDeclaredFields_thenTwoFields() {
// When
Field[] allFields = Person.class.getDeclaredFields();
// Then
assertEquals(2, allFields.length);
assertTrue(Arrays.stream(allFields).anyMatch(field ->
field.getName().equals(LAST_NAME_FIELD)
&& field.getType().equals(String.class))
);
assertTrue(Arrays.stream(allFields).anyMatch(field ->
field.getName().equals(FIRST_NAME_FIELD)
&& field.getType().equals(String.class))
);
}
@Test
public void givenEmployeeClass_whenGetDeclaredFields_thenOneField() {
// When
Field[] allFields = Employee.class.getDeclaredFields();
// Then
assertEquals(1, allFields.length);
assertTrue(Arrays.stream(allFields).anyMatch(field ->
field.getName().equals(EMPLOYEE_ID_FIELD)
&& field.getType().equals(int.class))
);
}
@Test
public void givenEmployeeClass_whenSuperClassGetDeclaredFields_thenOneField() {
// When
Field[] allFields = Employee.class.getSuperclass().getDeclaredFields();
// Then
assertEquals(2, allFields.length);
assertTrue(Arrays.stream(allFields).anyMatch(field ->
field.getName().equals(LAST_NAME_FIELD)
&& field.getType().equals(String.class))
);
assertTrue(Arrays.stream(allFields).anyMatch(field ->
field.getName().equals(FIRST_NAME_FIELD)
&& field.getType().equals(String.class))
);
}
@Test
public void givenEmployeeClass_whenGetDeclaredFieldsOnBothClasses_thenThreeFields() {
// When
Field[] personFields = Employee.class.getSuperclass().getDeclaredFields();
Field[] employeeFields = Employee.class.getDeclaredFields();
Field[] allFields = new Field[employeeFields.length + personFields.length];
Arrays.setAll(allFields, i -> (i < personFields.length ? personFields[i] : employeeFields[i - personFields.length]));
// Then
assertEquals(3, allFields.length);
assertTrue(Arrays.stream(allFields).anyMatch(field ->
field.getName().equals(LAST_NAME_FIELD)
&& field.getType().equals(String.class))
);
assertTrue(Arrays.stream(allFields).anyMatch(field ->
field.getName().equals(FIRST_NAME_FIELD)
&& field.getType().equals(String.class))
);
assertTrue(Arrays.stream(allFields).anyMatch(field ->
field.getName().equals(EMPLOYEE_ID_FIELD)
&& field.getType().equals(int.class))
);
}
@Test
public void givenEmployeeClass_whenGetDeclaredFieldsOnEmployeeSuperclassWithModifiersFilter_thenOneFields() {
// When
List<Field> personFields = Arrays.stream(Employee.class.getSuperclass().getDeclaredFields())
.filter(f -> Modifier.isPublic(f.getModifiers()) || Modifier.isProtected(f.getModifiers()))
.collect(Collectors.toList());
// Then
assertEquals(1, personFields.size());
assertTrue(personFields.stream().anyMatch(field ->
field.getName().equals(LAST_NAME_FIELD)
&& field.getType().equals(String.class))
);
}
@Test
public void givenMonthEmployeeClass_whenGetAllFields_thenThreeFields() {
// When
List<Field> allFields = getAllFields(MonthEmployee.class);
// Then
assertEquals(3, allFields.size());
assertTrue(allFields.stream().anyMatch(field ->
field.getName().equals(LAST_NAME_FIELD)
&& field.getType().equals(String.class))
);
assertTrue(allFields.stream().anyMatch(field ->
field.getName().equals(EMPLOYEE_ID_FIELD)
&& field.getType().equals(int.class))
);
assertTrue(allFields.stream().anyMatch(field ->
field.getName().equals(MONTH_EMPLOYEE_REWARD_FIELD)
&& field.getType().equals(double.class))
);
}
public List<Field> getAllFields(Class clazz) {
if (clazz == null) {
return Collections.emptyList();
}
List<Field> result = new ArrayList<>(getAllFields(clazz.getSuperclass()));
List<Field> filteredFields = Arrays.stream(clazz.getDeclaredFields())
.filter(f -> Modifier.isPublic(f.getModifiers()) || Modifier.isProtected(f.getModifiers()))
.collect(Collectors.toList());
result.addAll(filteredFields);
return result;
}
}