Spring – Constructor Injection with Non-String Map

In the constructor injection, the dependency injection will be injected with the help of constructors. Now to set the dependency injection as constructor dependency injection(CDI) in bean, it is done through the bean-configuration file For this, the property to be set with the constructor dependency injection is declared under the <constructor-arg> tag in the bean-config file.

Constructor Injection with Collection

Spring frameworks provide us the facility to inject collection values via constructor in our spring application. The following collections can be used inside the <constructor-arg> tag:

• list
• set
• map

Implementation: In the following example, we will see constructor injection with Map. The map will have both key and value as non-strings. Key will be Employee which has the following fields:

1. Name
2. Employee ID
3. Department

Value will be Address which has the following parameters:

• House No.
• Pincode
• State
• Country

A. Company.java

Java

// Java Program to Illustrate Company Class

package com.geeksforgeeks.org;

// Importing required classes
import com.geeksforgeeks.org.Address;
import com.geeksforgeeks.org.Employee;
import java.util.*;
import java.util.Map.Entry;

// Class
public class Company {

    // Class member variable
    private Map<Employee, Address> employees;

    // Constructor
    public Company(Map<Employee, Address> employees)
    {
        // This keyword refers to current instance itself
        this.employees = employees;
    }

    // Method
    public void display()
    {
        // Iterating over Map using for each loop
        for (Map.Entry<Employee, Address> entry :
             employees.entrySet()) {

            // Print statement
            System.out.println(
                "Employee Data ->"
                + entry.getKey().toString() + " Address ->"
                + entry.getValue().toString());
        }
    }
}

B. Employee.java

Java

// Java Program to Illustrate Employee Class

package com.geeksforgeeks.org;

// Importing required classes
import com.geeksforgeeks.org.Address;

// Class
public class Employee {

    // Class data members
    private String name;
    private String employeeID;
    private String department;

    public Employee(String name, String employeeID,
                    String department)
    {
        // This keyword refers to current instance itself
        this.name = name;
        this.employeeID = employeeID;
        this.department = department;
    }

    // Method
    // Overriding toString() method
    public String toString()
    {
        return ("[" + name + "," + employeeID + ","
                + department + "]");
    }
}

C. Address.java

Java

// Java Program to Illustrate Address Class

package com.geeksforgeeks.org;

// Class
public class Address {

    // Class data members
    private String houseNo;
    private String pincode;
    private String state;
    private String country;

    // Constructor
    public Address(String houseNo, String pincode,
                   String state, String country)
    {
        super();
        this.houseNo = houseNo;
        this.pincode = pincode;
        this.state = state;
        this.country = country;
    }

    // Method
    // Overriding toString() method
    public String toString()
    {
        return "[" + houseNo + "," + pincode + "," + state
            + "," + country + "]";
    }
}

D. applicationContext.xml

XML

<?xml version="1.0" encoding="UTF-8"?>
<beans
    xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:p="http://www.springframework.org/schema/p"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
     http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">

<bean id="employee1" class="com.geeksforgeeks.org.Employee">
    <constructor-arg value="Ram"></constructor-arg>
    <constructor-arg value="101"></constructor-arg>
    <constructor-arg value="Software development"></constructor-arg>
</bean>

<bean id="user1" class="com.geeksforgeeks.org.Address">
    <constructor-arg value="110/4"></constructor-arg>
    <constructor-arg value="128933"></constructor-arg>
    <constructor-arg value="Delhi"></constructor-arg>
      <constructor-arg value="India"></constructor-arg>
</bean>

<bean id="company" class="com.geeksforgeeks.org.Company">
    <constructor-arg>
        <map>
            <entry key-ref="employee1" value-ref="address1"></entry>
        </map>
    </constructor-arg>
</bean>

</beans>

E. Test.java

Java

// Java Program to Illustrate Application Class

package com.geeksforgeeks.org;

// importing required classes
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.xml.XmlBeanFactory;
import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.Resource;

// Application class
// Main class
public class Test {

    // Main driver method
    public static void main(String[] args)
    {
        // Creating a class path resource
        Resource resource = new ClassPathResource(
            "applicationContext.xml");

        // Creating an object of Beanfactory class
        BeanFactory factory = new XmlBeanFactory(resource);

        // Creating an object of Employee class
        Employee c = (Employee)factory.getBean("company");

        // Calling print() method inside main() method
        c.display();
    }
}

Output:

Employee Data -> [Ram, 101, software testing], Address -> [110/4, 128933, Delhi, India]