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Post about using reflection to get values of private members

17:32 suresh chaudhari 0 Comments


import java.io.IOException;

import java.lang.annotation.Retention;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.sql.SQLException;
import java.util.Arrays;
import java.util.Comparator;
import java.lang.annotation.RetentionPolicy;

/**Using reflection how to get values of member of class please go throught the code
**/
public class Student {

private String grade;

private String name;

private String id;

private String gender;

private Method[] methods;

@Retention(RetentionPolicy.RUNTIME)
public @interface Order {
    int value();
}

/**
 * Sort methods as per Order Annotations
 * 
 * @return
 */
private void sortMethods() {

 methods = Student.class.getMethods();

    Arrays.sort(methods, new Comparator() {
        public int compare(Method o1, Method o2) {
            Order or1 = o1.getAnnotation(Order.class);
            Order or2 = o2.getAnnotation(Order.class);
            if (or1 != null && or2 != null) {
                return or1.value() - or2.value();
            }
            else if (or1 != null && or2 == null) {
                return -1;
            }
            else if (or1 == null && or2 != null) {
                return 1;
            }
            return o1.getName().compareTo(o2.getName());
        }
    });
}

/**
 * Read Elements by Using method.invoke functionality
 * 
 * @return
 */
public void readElements() {
    int pos = 0;
    /**
     * Sort Methods
     */
    if (methods == null) {
        sortMethods();
    }
    for (Method method : methods) {
        String name = method.getName();
        if (name.startsWith("get") && !name.equalsIgnoreCase("getClass")) {
            pos++;
            String value = "";
            try {
                value = (String) method.invoke(this);
            }
            catch (IllegalAccessException | IllegalArgumentException | InvocationTargetException e) {
                e.printStackTrace();
            }
            System.out.println(name + " Pos: " + pos + " Value: " + value);
        }
    }
}
// /////////////////////// Getter and Setter Methods

/**
 * @param grade
 * @param name
 * @param id
 * @param gender
 */
public Student(String grade, String name, String id, String gender) {
    super();
    this.grade = grade;
    this.name = name;
    this.id = id;
    this.gender = gender;
}

/**
 * @return the grade
 */
@Order(value = 4)
public String getGrade() {
    return grade;
}

/**
 * @param grade the grade to set
 */
public void setGrade(String grade) {
    this.grade = grade;
}

/**
 * @return the name
 */
@Order(value = 2)
public String getName() {
    return name;
}

/**
 * @param name the name to set
 */
public void setName(String name) {
    this.name = name;
}

/**
 * @return the id
 */
@Order(value = 1)
public String getId() {
    return id;
}

/**
 * @param id the id to set
 */
public void setId(String id) {
    this.id = id;
}

/**
 * @return the gender
 */
@Order(value = 3)
public String getGender() {
    return gender;
}

/**
 * @param gender the gender to set
 */
public void setGender(String gender) {
    this.gender = gender;
}

/**
 * Main
 * 
 * @param args
 * @throws IOException
 * @throws SQLException
 * @throws InvocationTargetException
 * @throws IllegalArgumentException
 * @throws IllegalAccessException
 */
public static void main(String args[]) throws IOException, SQLException, IllegalAccessException,
        IllegalArgumentException, InvocationTargetException {
    Student student = new Student("A", "Anand", "001", "Male");
    student.readElements();
}
}

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