changelog.md

IOC

最简单的bean容器

分支：simple-bean-container

定义一个简单的bean容器BeanFactory，内部包含一个map用以保存bean，只有注册bean和获取bean两个方法

public class BeanFactory {
	private Map<String, Object> beanMap = new HashMap<>();

	public void registerBean(String name, Object bean) {
		beanMap.put(name, bean);
	}

	public Object getBean(String name) {
		return beanMap.get(name);
	}
}

测试：BeanFactoryTest

@Test
public void testGetBean() throws Exception {
    BeanFactory beanFactory = new BeanFactory();
    beanFactory.registerBean("helloService", new HelloService());

    HelloService helloService = (HelloService) beanFactory.getBean("helloService");
    assertThat(helloService).isNotNull();
    assertThat(helloService.sayHello()).isEqualTo("hello");
}

class HelloService {
    public String sayHello() {
        System.out.println("hello");
        return "hello";
    }
}

BeanDefinition和BeanDefinitionRegistry

分支：bean-definition-and-bean-definition-registry

主要增加如下类：

• BeanDefinition，顾名思义，用于定义bean信息的类，包含bean的class类型、构造参数、属性值等信息，每个bean对应一个BeanDefinition的实例。简化BeanDefition仅包含bean的class类型。
• BeanDefinitionRegistry，BeanDefinition注册表接口，定义注册BeanDefintion的方法。
• SingletonBeanRegistry及其实现类DefaultSingletonBeanRegistry，定义添加和获取单例bean的方法。

bean容器作为BeanDefinitionRegistry和SingletonBeanRegistry的实现类，具备两者的能力。向bean容器中注册BeanDefintion后，使用bean时才会实例化。

测试：BeanFactoryTest

@Test
public void testBeanFactory() throws Exception {
    DefaultListableBeanFactory beanFactory = new DefaultListableBeanFactory();
    BeanDefinition beanDefinition = new BeanDefinition(HelloService.class);
    beanFactory.registerBeanDefinition("helloService", beanDefinition);

    HelloService helloService = (HelloService) beanFactory.getBean("helloService");
    helloService.sayHello();
}

class HelloService {
	public String sayHello() {
		System.out.println("hello");
		return "hello";
	}
}

Bean实例化策略InstantiationStrategy

分支：instantiation-strategy

现在bean是在AbstractAutowireCapableBeanFactory.doCreateBean方法中用beanClass.newInstance()来实例化，仅适用于bean有无参构造函数的情况。针对bean的实例化，抽象出一个实例化策略的接口InstantiationStrategy，有两个实现类：

• SimpleInstantiationStrategy，使用bean的构造函数来实例化
• CglibSubclassingInstantiationStrategy，使用CGLIB动态生成子类

为bean填充属性

分支：populate-bean-with-property-values

在BeanDefinition中增加和bean属性对应的PropertyVales，实例化bean之后，为bean填充属性(AbstractAutowireCapableBeanFactory#applyPropertyValues)。 测试：BeanFactoryTest

@Test
public void testBeanFactory() throws Exception {
    DefaultListableBeanFactory beanFactory = new DefaultListableBeanFactory();
    PropertyValues propertyValues = new PropertyValues();
    propertyValues.addPropertyValue(new PropertyValue("foo", "hello"));
    propertyValues.addPropertyValue(new PropertyValue("bar", "world"));
    BeanDefinition beanDefinition = new BeanDefinition(HelloService.class, propertyValues);
    beanFactory.registerBeanDefinition("helloService", beanDefinition);

    HelloService helloService = (HelloService) beanFactory.getBean("helloService");
    System.out.println(helloService.toString());
    assertThat(helloService.getFoo()).isEqualTo("hello");
    assertThat(helloService.getBar()).isEqualTo("world");
}

public class HelloService {

	private String foo;

	private String bar;

	public String getFoo() {
		return foo;
	}

	public void setFoo(String foo) {
		this.foo = foo;
	}

	public String getBar() {
		return bar;
	}

	public void setBar(String bar) {
		this.bar = bar;
	}

	@Override
	public String toString() {
		return "HelloService{" +
				"foo='" + foo + '\'' +
				", bar='" + bar + '\'' +
				'}';
	}
}