Spring5核心原理-静态工厂方法详解

在 Spring 框架中，如果您想通过调用静态工厂方法来创建 bean ，其目的是将对象创建过程封装在static方法中，那么您可以使用factory-method属性。

静态工厂方法示例

如果你想EmployeeDTO基于它designation使用静态工厂方法创建不同的对象，你可以像下面的例子那样做。

public class EmployeeDTO {
 
    private Integer id;
    private String firstName;
    private String lastName;
 
    private String designation;
 
    //Setters and Getters
 
    @Override
    public String toString() {
        return "Employee [id=" + id + ", firstName=" + firstName
                + ", lastName=" + lastName + ", type=" + designation + "]";
    }
}

创建静态工厂方法。

public class EmployeeFactory {
     
    public static EmployeeDTO createEmployeeOfType(String type) 
    {
        if ("manager".equals(type) || "director".equals(type)) 
        {
            EmployeeDTO employee = new EmployeeDTO();
             
            employee.setId(-1);
            employee.setFirstName("dummy");
            employee.setLastName("dummy");
            //Set designation here
            employee.setDesignation(type);
             
            return employee;
        }
        else
        {
            throw new IllegalArgumentException("Unknown product");
        }
    }
}

使用factory-method属性来创建 bean。

<bean id="manager" class="com.leftso.demo.factory.EmployeeFactory"
    factory-method="createEmployeeOfType">
    <constructor-arg value="manager" />
</bean>
 
<bean id="director" class="com.leftso.demo.factory.EmployeeFactory"
    factory-method="createEmployeeOfType">
    <constructor-arg value="director" />
</bean>

演示

让我们测试一下静态工厂方法配置。

public class TestSpringStaticFactoryMethod 
{
    @SuppressWarnings("resource")
    public static void main(String[] args) throws Exception 
    {
        ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
 
        EmployeeDTO manager = (EmployeeDTO) context.getBean("manager");
        System.out.println(manager);
         
        EmployeeDTO director = (EmployeeDTO) context.getBean("director");
        System.out.println(director);
    }
}

在控制台中观察输出:

Employee [id=-1, firstName=dummy, lastName=dummy, type=manager]
Employee [id=-1, firstName=dummy, lastName=dummy, type=director]