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 Spring > Core > Constructor Argument Type Resolution

Constructor Argument Type Resolution 

Spring Inversion of Control (IoC) also known as Dependency Injection (DI) is a process by which objects define their dependencies with collaborating objects. Spring uses the arguments defined in the bean definition in the same order while invoking constructor as long as there is no ambiguity. For instance string "1234" might require to be injected as a either string or number depending on the context. Spring cannot resolve such ambiguity by itself. In such cases we can resolve the ambiguity by explicitly specifying argument type in bean definition.

File Name  :  
/SpringCore001/conf/cons/con_arg_type.xml 

File Name  :  
com/bethecoder/tutorials/spring3/basic/Employee.java 
   
package com.bethecoder.tutorials.spring3.basic;

public class Employee {
  
  private int id;
  private String name;
  private double salary;
  
  public Employee() {
    super();
    this.id = -1;
    this.name = "Unknown";
    this.salary = 0;
  }
  
  public Employee(int id, String name) {
    super();
    this.id = id;
    this.name = name;
    this.salary = 20000;
  }
  
  public Employee(int id, String name, double salary) {
    super();
    this.id = id;
    this.name = name;
    this.salary = salary;
  }

  public int getId() {
    return id;
  }
  
  public void setId(int id) {
    this.id = id;
  }
  
  public String getName() {
    return name;
  }
  
  public void setName(String name) {
    this.name = name;
  }
  
  public double getSalary() {
    return salary;
  }
  
  public void setSalary(double salary) {
    this.salary = salary;
  }
  
  public String toString() {
    return "Employee[" + id + ", " + name + ", " + salary + "]";
  }
  
}
   

File Name  :  
com/bethecoder/tutorials/spring3/tests/cons/ConstructorArgType.java 
Author  :  Sudhakar KV
Email  :  kvenkatasudhakar@gmail.com
   
package com.bethecoder.tutorials.spring3.tests.cons;

import org.springframework.beans.factory.xml.XmlBeanFactory;
import org.springframework.core.io.ClassPathResource;

import com.bethecoder.tutorials.spring3.basic.Employee;

public class ConstructorArgType {

  /**
   @param args
   */
  public static void main(String[] args) {
    XmlBeanFactory factory = new XmlBeanFactory(
                new ClassPathResource("con_arg_type.xml"));

    //Constructor argument type matching
    Employee emp1 = (Employeefactory.getBean("emp1");
    System.out.println(emp1);
    
    Employee emp2 = (Employeefactory.getBean("emp2");
    System.out.println(emp2);
  }

}
   

It gives the following output,
Employee[4, PQR, 80000.0]
Employee[5, MNO, 60000.9]


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