[Java Sprint] AutoWire

Previous we have seen constructore injection: https://www.cnblogs.com/Answer1215/p/9484872.html

It would be easier to using autowire to reduce the code, and autowite has four different types:

• byType
• byName
• constructor
• no

First let's see how to use 'autowire="constructor"':

    <bean name="customerService" class="com.pluralsight.service.CustomerServiceImpl" autowire="constructor">
        <!-- <constructor-arg index="0" ref="foo"></constructor-arg> -->
    </bean>

We comment out constructor injection and using autowire.

byName:

package com.pluralsight.service;

import com.pluralsight.model.Customer;
import com.pluralsight.repository.CustomerRepository;

import java.util.List;

public class CustomerServiceImpl implements CustomerService {

    //private CustomerRepository customerRepository = new HibernateCustomerRepositoryImpl();
    private CustomerRepository customerRepository;

    public CustomerServiceImpl () {

    }

    public CustomerServiceImpl (CustomerRepository customerRepository) {
        this.customerRepository = customerRepository;
    }

 // if set autowire by name, so in applicationContext <bean name="customerRepository" ..>
// if <bean name="foo" ..> then this function should be rename public void setFoo(CustomerRepository customerRepository)
    public void setCustomerRepository(CustomerRepository customerRepository) {
        this.customerRepository = customerRepository;
    }

    @Override
    public List<Customer> findAll() {
        return customerRepository.findAll();
    }

}

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

    <!-- Define a class, using implementation-->
    <bean name="customerRepository" class="com.pluralsight.repository.HibernateCustomerRepositoryImpl"></bean>

    <!-- Setter injection: Inject HibernateCustomerRepositoryImpl to customerRepository -->
    <bean name="customerService" class="com.pluralsight.service.CustomerServiceImpl" autowire="byName">
        <!--<property name="customerRepository" ref="foo"></property>-->
        <!-- <constructor-arg index="0" ref="foo"></constructor-arg> -->
    </bean>
</beans>

byType:

    <bean name="customerService" class="com.pluralsight.service.CustomerServiceImpl" autowire="byType">
        <!--<property name="customerRepository" ref="foo"></property>-->
        <!-- <constructor-arg index="0" ref="foo"></constructor-arg> -->
    </bean>

It doesn't matter we use 'name="customerService"' or 'name="foo"', because it finding by type, so still will work.