[BAEL-9175] Add various approaches for copying specific fields (#18430)

Co-authored-by: rajatgarg <[email protected]>

Author: rajat-garg

spring-core-4/src/main/java/com/baeldung/copyproperties/BeanUtilsCopyProperties.java

@@ -0,0 +1,19 @@
+package com.baeldung.copyproperties;
+
+import org.springframework.beans.BeanUtils;
+
+import java.beans.PropertyDescriptor;
+import java.util.Arrays;
+import java.util.Set;
+
+public class BeanUtilsCopyProperties {
+    public static void copySelectedPropertiesUsingCustomWrapper(Object source, Object target, Set<String> props) {
+        String[] excludedProperties = Arrays.stream(BeanUtils.getPropertyDescriptors(source.getClass()))
+                .map(PropertyDescriptor::getName)
+                .filter(name -> !props.contains(name))
+                .toArray(String[]::new);
+
+        BeanUtils.copyProperties(source, target, excludedProperties);
+    }
+
+}

spring-core-4/src/test/java/com/baeldung/copyproperties/BeanUtilsCopyPropertiesUnitTest.java

@@ -0,0 +1,48 @@
+package com.baeldung.copyproperties;
+
+import org.junit.Test;
+import org.springframework.beans.BeanUtils;
+
+import java.util.Arrays;
+import java.util.HashSet;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNull;
+
+public class BeanUtilsCopyPropertiesUnitTest {
+
+    @Test
+    public void givenObjects_whenUsingIgnoreProperties_thenCopyProperties() {
+        SourceBean sourceBean = new SourceBean("Peter", 30, "LA");
+        TargetBean targetBean = new TargetBean();
+
+        BeanUtils.copyProperties(sourceBean, targetBean, "address");
+        assertEquals(targetBean.getName(), sourceBean.getName());
+        assertEquals(targetBean.getAge(), sourceBean.getAge());
+        assertNull(targetBean.getAddress());
+    }
+
+    @Test
+    public void givenObjects_whenUsingIntermediateObject_thenCopyProperties() {
+        SourceBean sourceBean = new SourceBean("Peter", 30, "LA");
+        TempDTO tempDTO = new TempDTO();
+        BeanUtils.copyProperties(sourceBean, tempDTO);
+
+        TargetBean targetBean = new TargetBean();
+        BeanUtils.copyProperties(tempDTO, targetBean);
+        assertEquals(targetBean.getName(), sourceBean.getName());
+        assertEquals(targetBean.getAge(), sourceBean.getAge());
+        assertNull(targetBean.getAddress());
+    }
+
+    @Test
+    public void givenObjects_whenUsingCustomWrapper_thenCopyProperties() {
+        SourceBean sourceBean = new SourceBean("Peter", 30, "LA");
+        TargetBean targetBean = new TargetBean();
+        BeanUtilsCopyProperties.copySelectedPropertiesUsingCustomWrapper(sourceBean, targetBean, new HashSet<>(Arrays.asList("name", "age")));
+        System.out.println(targetBean);
+        assertEquals(targetBean.getName(), sourceBean.getName());
+        assertEquals(targetBean.getAge(), sourceBean.getAge());
+        assertNull(targetBean.getAddress());
+    }
+}

spring-core-4/src/test/java/com/baeldung/copyproperties/SourceBean.java

@@ -0,0 +1,37 @@
+package com.baeldung.copyproperties;
+
+public class SourceBean {
+    public String name;
+    public int age;
+    public String address;
+
+    public SourceBean(String name, int age, String address) {
+        this.name = name;
+        this.age = age;
+        this.address = address;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public int getAge() {
+        return age;
+    }
+
+    public void setAge(int age) {
+        this.age = age;
+    }
+
+    public String getAddress() {
+        return address;
+    }
+
+    public void setAddress(String address) {
+        this.address = address;
+    }
+}

spring-core-4/src/test/java/com/baeldung/copyproperties/TargetBean.java

@@ -0,0 +1,49 @@
+package com.baeldung.copyproperties;
+
+public class TargetBean {
+    public String name;
+    public int age;
+    public String address;
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public int getAge() {
+        return age;
+    }
+
+    public TargetBean() {
+    }
+
+    public TargetBean(String name, int age, String address) {
+        this.name = name;
+        this.age = age;
+        this.address = address;
+    }
+
+    public void setAge(int age) {
+        this.age = age;
+    }
+
+    public String getAddress() {
+        return address;
+    }
+
+    public void setAddress(String address) {
+        this.address = address;
+    }
+
+    @Override
+    public String toString() {
+        return "TargetBean{" +
+                "name='" + name + '\'' +
+                ", age=" + age +
+                ", address='" + address + '\'' +
+                '}';
+    }
+}

spring-core-4/src/test/java/com/baeldung/copyproperties/TempDTO.java

@@ -0,0 +1,30 @@
+package com.baeldung.copyproperties;
+
+public class TempDTO {
+    public String name;
+    public int age;
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public int getAge() {
+        return age;
+    }
+
+    public void setAge(int age) {
+        this.age = age;
+    }
+
+    public TempDTO(String name, int age) {
+        this.name = name;
+        this.age = age;
+    }
+
+    public TempDTO() {
+    }
+}