spring-framework源码第3弹------Spring IOC 容器的简单实现（学习tiny-spring）

声明：本代码来源于tiny-spring ，感谢原作者的源码
修改后的代码tiny-spring-copy

前言

学习Spring源码之前先学习下微缩版的Spring 框架—–tiny-spring 框架。闲话少说，先从IoC 容器开始。

IoC 的实现流程

1. 读取配置文件，获取资源输入流
2. 解析Bean，生成Bean的实例，
3. 根据依赖注入Bean的实例

读取配置文件

Resource 接口，标识一个外部资源，通过getInputStream()获取资源的输入流

public interface Resource { InputStream getInputStream() throws IOException;
}
  

 

  
1
  
2
  
3
  
4
 

UrlResource 实现Resource接口

public class UrlResource implements Resource { private final URL url; public UrlResource(URL url) { this.url = url; } @Override public InputStream getInputStream() throws IOException{ URLConnection urlConnection = url.openConnection(); urlConnection.connect(); return urlConnection.getInputStream(); }
}
  

 

  
1
  
2
  
3
  
4
  
5
  
6
  
7
  
8
  
9
  
10
  
11
  
12
  
13
  
14
  
15
 

ResourceLoader 接口，加载资源，返回UrlResource 对象

public interface ResourceLoader { /** * @param location * @return */ public Resource getResource(String location);
}
  

 

  
1
  
2
  
3
  
4
  
5
  
6
  
7
 

UrlResourceLoader类实现ResourceLoader接口

public class UrlResourceLoader implements ResourceLoader { @Override public Resource getResource(String location){ URL resource = this.getClass().getClassLoader().getResource(location); return new UrlResource(resource); }
}
  

 

  
1
  
2
  
3
  
4
  
5
  
6
  
7
  
8
 

解析配置文件，获取Bean的定义

1. BeanDefinition 实体类，用于存放Bean的定义，包括Bean的内容和属性

public class BeanDefinition { /** * */ private Object bean; /** * Bean的类型 */ private Class beanClass; /** * Bean的名称 */ private String beanClassName; /** * 属性类，内部封装了一个List<PropertyValue> */ private PropertyValues propertyValues = new PropertyValues(); get和set方法省略

}
  

 

  
1
  
2
  
3
  
4
  
5
  
6
  
7
  
8
  
9
  
10
  
11
  
12
  
13
  
14
  
15
  
16
  
17
  
18
  
19
  
20
  
21
  
22
  
23
  
24
  
25
 

1. BeanDefinitionReader 解析 BeanDefinition接口，通过loadBeanDefinitions（String） 从一个地址加载类的定义

public interface BeanDefinitionReader { /** * 从配置中读取BeanDefinition * @param location * @throws Exception */ void loadBeanDefinitions(String location) throws Exception;
}
  

 

  
1
  
2
  
3
  
4
  
5
  
6
  
7
  
8
  
9
 

1. AbstractBeanDefinitionReader
   实现BeanDefinitionReader接口的抽象类，未具体实现loadBeanDefinitions（String），主要是规范了BeanDefinitionReader的基本结构，

public abstract class AbstractBeanDefinitionReader implements BeanDefinitionReader { //用于保存String - beanDefinition 的键值对 private Map<String,BeanDefinition> registry; //用于保存类加载器 private UrlResourceLoader resourceLoader; protected AbstractBeanDefinitionReader(UrlResourceLoader resourceLoader) { this.registry = new HashMap<String, BeanDefinition>(); this.resourceLoader = resourceLoader; } public Map<String, BeanDefinition> getRegistry() { return registry; } public UrlResourceLoader getResourceLoader() { return resourceLoader; }
}
  

 

  
1
  
2
  
3
  
4
  
5
  
6
  
7
  
8
  
9
  
10
  
11
  
12
  
13
  
14
  
15
  
16
  
17
  
18
  
19
 

1. XmlBeanDefinitionReader类，具体实现BeanDefinitionReader接口，从配置文件中获取Bean的定义

public class XmlBeanDefinitionReader extends AbstractBeanDefinitionReader { public XmlBeanDefinitionReader(UrlResourceLoader resourceLoader) { super(resourceLoader); } @Override public void loadBeanDefinitions(String location) throws Exception { InputStream inputStream = getResourceLoader().getResource(location).getInputStream(); doLoadBeanDefinitions(inputStream); } protected void doLoadBeanDefinitions(InputStream inputStream) throws Exception { DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance(); DocumentBuilder docBuilder = factory.newDocumentBuilder(); Document doc = docBuilder.parse(inputStream); // 解析bean registerBeanDefinitions(doc); inputStream.close(); } /** * 解析Bean * @param doc */ public void registerBeanDefinitions(Document doc) { Element root = doc.getDocumentElement(); parseBeanDefinitions(root); } /** * 解析Bean * @param root */ protected void parseBeanDefinitions(Element root) { NodeList nl = root.getChildNodes(); for (int i = 0; i < nl.getLength(); i++) { Node node = nl.item(i); if (node instanceof Element) { Element ele = (Element) node; processBeanDefinition(ele); } } } /** * 解析Bean中的id和class,以及其他属性 * @param ele */ protected void processBeanDefinition(Element ele) { String name = ele.getAttribute("id"); String className = ele.getAttribute("class"); BeanDefinition beanDefinition = new BeanDefinition(); //保存属性 processProperty(ele, beanDefinition); //保存类全限定名 beanDefinition.setBeanClassName(className); //将获得的Bean的定义保存到map中 getRegistry().put(name, beanDefinition); } /** * 解析Bean中的property属性 * @param ele * @param beanDefinition */ private void processProperty(Element ele, BeanDefinition beanDefinition) { NodeList propertyNode = ele.getElementsByTagName("property"); for (int i = 0; i < propertyNode.getLength(); i++) { Node node = propertyNode.item(i); if (node instanceof Element) { Element propertyEle = (Element) node; String name = propertyEle.getAttribute("name"); String value = propertyEle.getAttribute("value"); if (value != null && value.length() > 0) { beanDefinition.getPropertyValues().addPropertyValue(new PropertyValue(name, value)); } else { String ref = propertyEle.getAttribute("ref"); if (ref == null || ref.length() == 0) { throw new IllegalArgumentException("Configuration problem: <property> element for property '" + name + "' must specify a ref or value"); } BeanReference beanReference = new BeanReference(ref); beanDefinition.getPropertyValues().addPropertyValue(new PropertyValue(name, beanReference)); } } } }
}

  

 

  
1
  
2
  
3
  
4
  
5
  
6
  
7
  
8
  
9
  
10
  
11
  
12
  
13
  
14
  
15
  
16
  
17
  
18
  
19
  
20
  
21
  
22
  
23
  
24
  
25
  
26
  
27
  
28
  
29
  
30
  
31
  
32
  
33
  
34
  
35
  
36
  
37
  
38
  
39
  
40
  
41
  
42
  
43
  
44
  
45
  
46
  
47
  
48
  
49
  
50
  
51
  
52
  
53
  
54
  
55
  
56
  
57
  
58
  
59
  
60
  
61
  
62
  
63
  
64
  
65
  
66
  
67
  
68
  
69
  
70
  
71
  
72
  
73
  
74
  
75
  
76
  
77
  
78
  
79
  
80
  
81
  
82
  
83
  
84
  
85
  
86
  
87
  
88
  
89
  
90
  
91
  
92
 

注册生成Bean的实例 以及使用该实例

BeanFactory类，标识一个IoC容器，通过getBean(String)来获取Bean的实例。

public interface BeanFactory { Object getBean(String name) throws Exception;

}
  

 

  
1
  
2
  
3
  
4
  
5
 

AbstractBeanFactory类，BeanFactory的一种抽象实现，规范了IoC容器的基本结构，但是把生成Bean的具体方式留给了子类来实现。

public abstract class AbstractBeanFactory implements BeanFactory { private Map<String, BeanDefinition> beanDefinitionMap = new ConcurrentHashMap<String, BeanDefinition>(); private final List<String> beanDefinitionNames = new ArrayList<String>(); private List<BeanPostProcessor> beanPostProcessors = new ArrayList<BeanPostProcessor>(); @Override public Object getBean(String name) throws Exception { BeanDefinition beanDefinition = beanDefinitionMap.get(name); if (beanDefinition == null) { throw new IllegalArgumentException("No bean named " + name + " is defined"); } Object bean = beanDefinition.getBean(); //如果bean存在，则返回。否则调用doCreateBean方法装配一个Bean if (bean == null) { bean = doCreateBean(beanDefinition); bean = initializeBean(bean, name); beanDefinition.setBean(bean); } return bean; } /** * 对Bean做初始化 * @param bean * @param name * @return * @throws Exception */ protected Object initializeBean(Object bean, String name) throws Exception { for (BeanPostProcessor beanPostProcessor : beanPostProcessors) { bean = beanPostProcessor.postProcessBeforeInitialization(bean, name); } // TODO:call initialize method for (BeanPostProcessor beanPostProcessor : beanPostProcessors) { bean = beanPostProcessor.postProcessAfterInitialization(bean, name); } return bean; } protected Object createBeanInstance(BeanDefinition beanDefinition) throws Exception { return beanDefinition.getBeanClass().newInstance(); } public void registerBeanDefinition(String name, BeanDefinition beanDefinition) throws Exception { beanDefinitionMap.put(name, beanDefinition); beanDefinitionNames.add(name); } public void preInstantiateSingletons() throws Exception { for (Iterator it = this.beanDefinitionNames.iterator(); it.hasNext();) { String beanName = (String) it.next(); getBean(beanName); } } /** * 创建一个Bean的实例 * @param beanDefinition * @return * @throws Exception */ protected Object doCreateBean(BeanDefinition beanDefinition) throws Exception { Object bean = createBeanInstance(beanDefinition); beanDefinition.setBean(bean); applyPropertyValues(bean, beanDefinition); return bean; } protected void applyPropertyValues(Object bean, BeanDefinition beanDefinition) throws Exception { } public void addBeanPostProcessor(BeanPostProcessor beanPostProcessor) throws Exception { this.beanPostProcessors.add(beanPostProcessor); } public List getBeansForType(Class type) throws Exception { List beans = new ArrayList<Object>(); for (String beanDefinitionName : beanDefinitionNames) { if (type.isAssignableFrom(beanDefinitionMap.get(beanDefinitionName).getBeanClass())) { beans.add(getBean(beanDefinitionName)); } } return beans; }

}

  

 

  
1
  
2
  
3
  
4
  
5
  
6
  
7
  
8
  
9
  
10
  
11
  
12
  
13
  
14
  
15
  
16
  
17
  
18
  
19
  
20
  
21
  
22
  
23
  
24
  
25
  
26
  
27
  
28
  
29
  
30
  
31
  
32
  
33
  
34
  
35
  
36
  
37
  
38
  
39
  
40
  
41
  
42
  
43
  
44
  
45
  
46
  
47
  
48
  
49
  
50
  
51
  
52
  
53
  
54
  
55
  
56
  
57
  
58
  
59
  
60
  
61
  
62
  
63
  
64
  
65
  
66
  
67
  
68
  
69
  
70
  
71
  
72
  
73
  
74
  
75
  
76
  
77
  
78
  
79
  
80
  
81
  
82
  
83
  
84
  
85
  
86
  
87
  
88
  
89
  
90
  
91
  
92
 

AutowireCapableBeanFactory 可以实现自动装配的 BeanFactory。在这个工厂中，实现了doCreateBean方法，该方法分为三步：1. 通过BeanDefinition中保存的类信息实例化一个对象；2.将对象保存在BeanDefinition中，以备下次获取；3. 为其装配属性。在装配属性时，通过BeanDefinition中维护的PropertyValues集合类，把String-Value键值对注入到Bean的属性中去。如果Value的类型是BeanReference，则说明其是一个引用（对应于XML中的ref）,通过getBean对其进行获取，然后注入到属性中。

public class AutowireCapableBeanFactory extends AbstractBeanFactory { /** * 将读取到的property值设置到Bean中 * @param bean * @param mbd * @throws Exception */ protected void applyPropertyValues(Object bean, BeanDefinition mbd) throws Exception { if (bean instanceof BeanFactoryAware) { ((BeanFactoryAware) bean).setBeanFactory(this); } for (PropertyValue propertyValue : mbd.getPropertyValues().getPropertyValues()) { Object value = propertyValue.getValue(); if (value instanceof BeanReference) { BeanReference beanReference = (BeanReference) value; value = getBean(beanReference.getName()); } try { Method declaredMethod = bean.getClass().getDeclaredMethod( "set" + propertyValue.getName().substring(0, 1).toUpperCase() + propertyValue.getName().substring(1), value.getClass()); declaredMethod.setAccessible(true); //反射方式设值 declaredMethod.invoke(bean, value); } catch (NoSuchMethodException e) { Field declaredField = bean.getClass().getDeclaredField(propertyValue.getName()); declaredField.setAccessible(true); declaredField.set(bean, value); } } }
}

  

 

  
1
  
2
  
3
  
4
  
5
  
6
  
7
  
8
  
9
  
10
  
11
  
12
  
13
  
14
  
15
  
16
  
17
  
18
  
19
  
20
  
21
  
22
  
23
  
24
  
25
  
26
  
27
  
28
  
29
  
30
  
31
  
32
  
33
  
34
  
35
  
36
 

ApplicationContext 接口以及其实现类，主要是对Resource,BeanFactory,BeanDefinition进行功能封装，解决根据地址获取IoC容器并使用的问题。
AbstractApplicationContext 类，ApplicationContext 的抽象实现，内部包含一个 BeanFactory 类

public abstract class AbstractApplicationContext implements ApplicationContext { protected AbstractBeanFactory beanFactory; public AbstractApplicationContext(AbstractBeanFactory beanFactory) { this.beanFactory = beanFactory; } public void refresh() throws Exception { loadBeanDefinitions(beanFactory); registerBeanPostProcessors(beanFactory); onRefresh(); } protected abstract void loadBeanDefinitions(AbstractBeanFactory beanFactory) throws Exception; protected void registerBeanPostProcessors(AbstractBeanFactory beanFactory) throws Exception { List beanPostProcessors = beanFactory.getBeansForType(BeanPostProcessor.class); for (Object beanPostProcessor : beanPostProcessors) { beanFactory.addBeanPostProcessor((BeanPostProcessor) beanPostProcessor); } } protected void onRefresh() throws Exception{ beanFactory.preInstantiateSingletons(); } @Override public Object getBean(String name) throws Exception { return beanFactory.getBean(name); }
}
  

 

  
1
  
2
  
3
  
4
  
5
  
6
  
7
  
8
  
9
  
10
  
11
  
12
  
13
  
14
  
15
  
16
  
17
  
18
  
19
  
20
  
21
  
22
  
23
  
24
  
25
  
26
  
27
  
28
  
29
  
30
  
31
 

ClassPathXmlApplicationContext 类，从类路径加载资源的具体实现类

public class ClassPathXmlApplicationContext extends AbstractApplicationContext { private String configLocation; public ClassPathXmlApplicationContext(String configLocation) throws Exception { this(configLocation, new AutowireCapableBeanFactory()); } public ClassPathXmlApplicationContext(String configLocation, AbstractBeanFactory beanFactory) throws Exception { super(beanFactory); this.configLocation = configLocation; refresh(); } @Override protected void loadBeanDefinitions(AbstractBeanFactory beanFactory) throws Exception { XmlBeanDefinitionReader xmlBeanDefinitionReader = new XmlBeanDefinitionReader(new UrlResourceLoader()); xmlBeanDefinitionReader.loadBeanDefinitions(configLocation); for (Map.Entry<String, BeanDefinition> beanDefinitionEntry : xmlBeanDefinitionReader.getRegistry().entrySet()) { beanFactory.registerBeanDefinition(beanDefinitionEntry.getKey(), beanDefinitionEntry.getValue()); } }
  

 

  
1
  
2
  
3
  
4
  
5
  
6
  
7
  
8
  
9
  
10
  
11
  
12
  
13
  
14
  
15
  
16
  
17
  
18
  
19
  
20
  
21
  
22
 

tiny-spring 的ApplicaitonContext使用流程是这样的：

1. ApplicaitonContext完成了类定义的读取和加载，并注册到BeanFactory中去。
2. ApplicaitonContext从BeanFactory中寻找BeanPostProcessor,注册到BeanFactory维护的BeanPostProcessor列表中去。
3. ApplicaitonContext以单例的模式，通过主动调用getBean实例化、注入属性、然后初始化BeanFactory中所有的Bean。由于所有的BeanPostProcessor都已经在第2步中完成实例化了，因此接下来实例化的是普通Bean,因此普通Bean的初始化过程可以正常执行。
4. 调用getBean时，委托给BeanFactory,此时只是简单的返回每个Bean单例，因为所有的Bean实例在第三步都已经生成了。

参考

https://www.zybuluo.com/dugu9sword/note/382745#%E6%96%87%E4%BB%B6%E7%BB%93%E6%9E%84

文章来源: feige.blog.csdn.net，作者：码农飞哥，版权归原作者所有，如需转载，请联系作者。

原文链接：feige.blog.csdn.net/article/details/80505620