Adding new Project : Spring check if a property is null

Using Java Introspector to check if a field is null in an object

.gitignore

@@ -37,3 +37,7 @@ spring-all/*.log
 *.jar
 
 SpringDataInjectionDemo/.mvn/wrapper/maven-wrapper.properties
+
+spring-call-getters-using-reflection/.mvn/wrapper/maven-wrapper.properties
+
+spring-check-if-a-property-is-null/.mvn/wrapper/maven-wrapper.properties

spring-check-if-a-property-is-null/.gitignore

@@ -0,0 +1,24 @@
+target/
+!.mvn/wrapper/maven-wrapper.jar
+
+### STS ###
+.apt_generated
+.classpath
+.factorypath
+.project
+.settings
+.springBeans
+
+### IntelliJ IDEA ###
+.idea
+*.iws
+*.iml
+*.ipr
+
+### NetBeans ###
+nbproject/private/
+build/
+nbbuild/
+dist/
+nbdist/
+.nb-gradle/

spring-check-if-a-property-is-null/pom.xml

@@ -0,0 +1,50 @@
+<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+	<modelVersion>4.0.0</modelVersion>
+
+	<groupId>baeldung</groupId>
+	<artifactId>spring-check-null</artifactId>
+	<version>0.0.1-SNAPSHOT</version>
+	<packaging>jar</packaging>
+
+	<name>spring-check-if-a-property-is-null</name>
+	<description>Calling getters using Introspector</description>
+
+	<parent>
+		<groupId>org.springframework.boot</groupId>
+		<artifactId>spring-boot-starter-parent</artifactId>
+		<version>1.5.3.RELEASE</version>
+		<relativePath/> <!-- lookup parent from repository -->
+	</parent>
+
+	<properties>
+		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+		<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
+		<java.version>1.8</java.version>
+	</properties>
+
+	<dependencies>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter</artifactId>
+		</dependency>
+
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-test</artifactId>
+			<scope>test</scope>
+		</dependency>
+	</dependencies>
+
+	<build>
+		<plugins>
+			<plugin>
+				<groupId>org.springframework.boot</groupId>
+				<artifactId>spring-boot-maven-plugin</artifactId>
+			</plugin>
+		</plugins>
+	</build>
+
+
+</project>

spring-check-if-a-property-is-null/src/main/java/com/baeldung/SpringCheckIfAPropertyIsNullApplication.java

@@ -0,0 +1,21 @@
+package com.baeldung;
+
+import java.util.List;
+
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+import com.baeldung.reflection.model.Customer;
+import com.baeldung.reflection.util.Utils;
+
+@SpringBootApplication
+public class SpringCheckIfAPropertyIsNullApplication {
+
+	public static void main(String[] args) throws Exception {
+	    
+	    Customer customer = new Customer(1, "Himanshu", null, null);
+	    List<String> nullProps = Utils.getNullPropertiesList(customer);
+	    System.out.println(nullProps);
+	}
+	
+	
+}

spring-check-if-a-property-is-null/src/main/java/com/baeldung/reflection/model/Customer.java

@@ -0,0 +1,63 @@
+package com.baeldung.reflection.model;
+
+/**
+ * 
+ * @author himanshumantri
+ *
+ */
+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() {
+        StringBuilder builder = new StringBuilder();
+        builder.append("Customer [id=").append(id).append(", name=").append(name).append(", emailId=").append(emailId).append(", phoneNumber=")
+                .append(phoneNumber).append("]");
+        return builder.toString();
+    }
+
+    public 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;
+    }
+
+}

spring-check-if-a-property-is-null/src/main/java/com/baeldung/reflection/util/Utils.java

@@ -0,0 +1,34 @@
+package com.baeldung.reflection.util;
+
+import java.beans.Introspector;
+import java.beans.PropertyDescriptor;
+import java.lang.reflect.Method;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+import com.baeldung.reflection.model.Customer;
+
+public class Utils {
+
+    public static List<String> getNullPropertiesList(Customer customer) throws Exception {
+        PropertyDescriptor[] propDescArr = Introspector.getBeanInfo(Customer.class, Object.class).getPropertyDescriptors();
+        List<PropertyDescriptor>  propDescList = Arrays.asList(propDescArr);
+        
+        List<String> nullProps = new ArrayList<String>();
+        
+        propDescList.stream().forEach(p -> {
+            Method getterMethod = p.getReadMethod();
+            try {
+                if (getterMethod != null && getterMethod.invoke(customer) == null) {
+                    // If the value if null for that field
+                    nullProps.add(p.getName());
+                }
+            } catch (Exception e) {
+                // Handle the exception
+                e.printStackTrace();
+            }
+        });
+        return nullProps;
+    }
+}

spring-check-if-a-property-is-null/src/test/java/com/baeldung/SpringCheckIfAPropertyIsNullApplicationTests.java

@@ -0,0 +1,31 @@
+package com.baeldung;
+
+import java.util.Arrays;
+import java.util.List;
+
+import org.junit.Assert;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.test.context.junit4.SpringRunner;
+
+import com.baeldung.reflection.model.Customer;
+import com.baeldung.reflection.util.Utils;
+
+@RunWith(SpringRunner.class)
+@SpringBootTest
+public class SpringCheckIfAPropertyIsNullApplicationTests {
+
+	@Test
+	public void givenCustomer_whenAFieldIsNull_thenFieldNameInResult() throws Exception {
+	    Customer customer = new Customer(1, "Himanshu", null, null);
+	    
+	    List<String> result = Utils.getNullPropertiesList(customer);
+	    List<String> expectedFieldNames = Arrays.asList("emailId","phoneNumber");
+	    
+        Assert.assertTrue(result.size() == expectedFieldNames.size());
+        Assert.assertTrue(result.containsAll(expectedFieldNames));
+        
+	}
+
+}