How to use ReflectionUtils to retrieve the field value

In this post, I am going to show how we can use the ReflectionUtils to get the field value from an object.

Most of the time, we use Java Reflection to retrieve the value but if the field is in the Super class, then you have to write some boilerplate code to retrieve those. But if you use ReflectionUtils, then you won’t have to worry about that.

Refer the below example,

BaseProfile and Employee are the two value objects. Here the Employee class extends BaseProfile class which has some common fields. Then in ReflectionUtilsMain, I am using Java reflection and also ReflectionUtils to retrieve the value of “firstName” field

Let’s check the code.

BaseProfile.java


import org.apache.commons.lang.builder.ReflectionToStringBuilder;
import org.apache.commons.lang3.builder.EqualsBuilder;
import org.apache.commons.lang3.builder.HashCodeBuilder;


public class BaseProfile {

    private String firstName;

    private String lastName;

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    @Override
    public String toString() {
        return ReflectionToStringBuilder.toString(this);
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;

        if (o == null || getClass() != o.getClass()) return false;

        BaseProfile that = (BaseProfile) o;

        return new EqualsBuilder()
                .append(firstName, that.firstName)
                .append(lastName, that.lastName)
                .isEquals();
    }

    @Override
    public int hashCode() {
        return new HashCodeBuilder(17, 37)
                .append(firstName)
                .append(lastName)
                .toHashCode();
    }
}

BaseProfile.java


import org.apache.commons.lang.builder.ReflectionToStringBuilder;
import org.apache.commons.lang3.builder.EqualsBuilder;
import org.apache.commons.lang3.builder.HashCodeBuilder;


public class Employee extends BaseProfile {

    private String empId;

    private String designation;

    public String getEmpId() {
        return empId;
    }

    public void setEmpId(String empId) {
        this.empId = empId;
    }

    public String getDesignation() {
        return designation;
    }

    public void setDesignation(String designation) {
        this.designation = designation;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;

        if (o == null || getClass() != o.getClass()) return false;

        Employee employee = (Employee) o;

        return new EqualsBuilder()
                .appendSuper(super.equals(o))
                .append(empId, employee.empId)
                .append(designation, employee.designation)
                .isEquals();
    }

    @Override
    public int hashCode() {
        return new HashCodeBuilder(17, 37)
                .appendSuper(super.hashCode())
                .append(empId)
                .append(designation)
                .toHashCode();
    }

    @Override
    public String toString() {
        return ReflectionToStringBuilder.toString(this);
    }
}

Here is our main class
ReflectionUtilsMain.java


import org.apache.commons.lang3.exception.ExceptionUtils;
import org.apache.commons.lang3.reflect.FieldUtils;

import java.lang.reflect.Field;

public class ReflectionUtilsMain {

    public static void main(String[] args) {

        Employee employee = new Employee();
        employee.setEmpId("1234");
        employee.setFirstName("John");
        employee.setLastName("Turner");
        employee.setDesignation("Manager");
        System.out.println(employee);

        //Now you want to access the First Name from Employee object with Java reflection
        String firstName = null;
        String fieldName = "firstName";
        for (Class aClass = employee.getClass(); aClass != null; aClass = aClass.getSuperclass()) {
            System.out.println("aClass:" + aClass.getSimpleName());
            try {
                Field field = aClass.getDeclaredField(fieldName);
                if (!field.isAccessible()) {
                    System.out.println("Field is found "+field);
                    field.setAccessible(true);
                    firstName = (String) field.get(employee);
                    break;
                }
            } catch (NoSuchFieldException | IllegalAccessException e) {
                System.err.print(ExceptionUtils.getStackTrace(e));
            }
        }
        System.out.println("Using Reflection firstName:" + firstName);
        firstName = null;
        //You can also use ReflectionUtils to get this very easily
        try {
            Field field = FieldUtils.getField(employee.getClass(), fieldName, true);
            firstName = (String) field.get(employee);
        } catch (Exception e) {
            System.err.print(ExceptionUtils.getStackTrace(e));
        }
        System.out.println("Using Reflection Utils firstName:" + firstName);

    }
}

The output will be like this,


java.lang.NoSuchFieldException: firstName
	at java.lang.Class.getDeclaredField(Class.java:2070)
	at org.cas.osd.mp.ReflectionUtilsMain.main(ReflectionUtilsMain.java:29)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at com.intellij.rt.execution.application.AppMain.main(AppMain.java:140)
org.cas.osd.mp.Employee@42110406[empId=1234,designation=Manager,firstName=John,lastName=Turner]
aClass:Employee
aClass:BaseProfile
Field is found private java.lang.String org.cas.osd.mp.BaseProfile.firstName
Using Reflection firstName:John
Using Reflection Utils firstName:John

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s