I getting class by name and i need to update them with respective data and my question is how to do it with java
I want to add the method some dummy data .
I don't know the class type I just getting the class name and use reflection to get his data
I use this code to get the class instance and
Class<?> classHandle = Class.forName(className);
Object myObject = classHandle.newInstance();
// iterate through all the methods declared by the class
for (Method method : classHandle.getMethods()) {
// find all the set methods
if (method.getName().matches("set[A-Z].*")
And know that I find the list of the set method I want to update it with data
how can I do that .
assume that In class name I got person and the class have setSalary and setFirstName etc
how can I set them with reflection ?
public class Person {
public void setSalery(double salery) {
this.salery = salery;
}
public void setFirstName(String FirstName) {
this.FirstName = FirstName;
}
}
Instead of trying to call a setter, you could also just directly set the value to the property using reflection. For example:
public static boolean set(Object object, String fieldName, Object fieldValue) {
Class<?> clazz = object.getClass();
while (clazz != null) {
try {
Field field = clazz.getDeclaredField(fieldName);
field.setAccessible(true);
field.set(object, fieldValue);
return true;
} catch (NoSuchFieldException e) {
clazz = clazz.getSuperclass();
} catch (Exception e) {
throw new IllegalStateException(e);
}
}
return false;
}
Call:
Class<?> clazz = Class.forName(className);
Object instance = clazz.newInstance();
set(instance, "salary", 15);
set(instance, "firstname", "John");
FYI, here is the equivalent generic getter:
@SuppressWarnings("unchecked")
public static <V> V get(Object object, String fieldName) {
Class<?> clazz = object.getClass();
while (clazz != null) {
try {
Field field = clazz.getDeclaredField(fieldName);
field.setAccessible(true);
return (V) field.get(object);
} catch (NoSuchFieldException e) {
clazz = clazz.getSuperclass();
} catch (Exception e) {
throw new IllegalStateException(e);
}
}
return null;
}
Call:
Class<?> clazz = Class.forName(className);
Object instance = clazz.newInstance();
int salary = get(instance, "salary");
String firstname = get(instance, "firstname");
if (method.getName().matches("set[A-Z].*") {
method.invoke(person,salary)
// and so on
}
to know the parameters you can issue method.getPagetParameterTypes()
based on the result construct your parameters and supply.
To update the first name
- First find the field you want to update
- Then find the mutator (which accepts an argument of the field's type)
- Finally execute the mutator on the object with the new value:
Field field=classHandle.getDeclaredField("firstName");
Method setter=classHandle.getMethod("setFirstName", field.getType());
setter.invoke(myObject, "new value for first name");
package apple;
import java.lang.reflect.Field;
import java.lang.reflect.Type;
import java.util.Map.Entry;
import java.util.Set;
import com.google.gson.Gson;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;
import com.google.gson.JsonSyntaxException;
/*
* Employe Details class
*/
class Employee {
private long id;
private String name;
private String userName;
private Address address;
private Contact contact;
private double salary;
public long getId() {
return id;
}
public void setId(long id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getUserName() {
return userName;
}
public void setUserName(String userName) {
this.userName = userName;
}
public Address getAddress() {
return address;
}
public void setAddress(Address address) {
this.address = address;
}
public Contact getContact() {
return contact;
}
public void setContact(Contact contact) {
this.contact = contact;
}
public double getSalary() {
return salary;
}
public void setSalary(double salary) {
this.salary = salary;
}
}
/*
* Address class for employee
*/
class Address {
private String city;
private String state;
private String country;
private int pincode;
public String getCity() {
return city;
}
public void setCity(String city) {
this.city = city;
}
public String getState() {
return state;
}
public void setState(String state) {
this.state = state;
}
public String getCountry() {
return country;
}
public void setCountry(String country) {
this.country = country;
}
public int getPincode() {
return pincode;
}
public void setPincode(int pincode) {
this.pincode = pincode;
}
}
/*
* Contact class for Employee
*/
class Contact {
private String email;
private String contactNo;
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
public String getContactNo() {
return contactNo;
}
public void setContactNo(String contactNo) {
this.contactNo = contactNo;
}
}
public class Server {
public static void main(String args[]) throws JsonSyntaxException, Exception{
Gson gson = new Gson();
/*
* Old Employee Data
*/
Address address = new Address();
Contact contact = new Contact();
Employee employee = new Employee();
address.setCity("shohna-road");
address.setCountry("INDIA");
address.setPincode(12201);
address.setState("Hariyana");
contact.setContactNo("+918010327919");
contact.setEmail("shivritesh9984@gmail.com");
employee.setAddress(address);
employee.setContact(contact);
employee.setId(4389573);
employee.setName("RITESH SINGH");
employee.setSalary(43578349.345);
employee.setUserName("ritesh9984");
System.out.println("Employee : "+gson.toJson(employee));
/* New employee data */
Employee emp = employee;
address.setCity("OMAX");
emp.setAddress(address);
emp.setName("RAVAN");
/* Update employee with new employee Object*/
update(employee, gson.fromJson(gson.toJson(emp), JsonObject.class) );
System.out.println("Employee-Update : "+gson.toJson(employee));
}
/*
* This method update the @target with new given value of new object in json object form
*/
public static void update(Object target, JsonObject json) throws Exception {
Gson gson=new Gson();
Class<? > class1 = target.getClass();
Set<Entry<String, JsonElement>> entrySet = json.entrySet();
for (Entry<String, JsonElement> entry : entrySet) {
String key = entry.getKey();
Field field = class1.getDeclaredField(key);
field.setAccessible(true);
Type genType = field.getGenericType();
field.set(target,
gson.fromJson(entry.getValue(),genType));
}
}
}
