Spring-spring-components

pull/20/head
huifer 5 years ago
parent d6789ae619
commit 7606ab6252

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# Spring5 新特性 - spring.components
- Author: [HuiFer](https://github.com/huifer)
- 源码阅读仓库: [huifer-spring](https://github.com/huifer/spring-framework-read)
## 解析
- 相关类: `org.springframework.context.index.CandidateComponentsIndexLoader`
- 测试用例: `org.springframework.context.annotation.ClassPathScanningCandidateComponentProviderTests.defaultsWithIndex`,`org.springframework.context.index.CandidateComponentsIndexLoaderTests`
- `CandidateComponentsIndexLoader`是怎么找出来的,全文搜索`spring.components`
### 使用介绍
- 下面是从`resources/example/scannable/spring.components`测试用例中复制过来的,从中可以发现等号左侧放的是我们写的组件,等号右边是属于什么组件
```
example.scannable.AutowiredQualifierFooService=example.scannable.FooService
example.scannable.DefaultNamedComponent=org.springframework.stereotype.Component
example.scannable.NamedComponent=org.springframework.stereotype.Component
example.scannable.FooService=example.scannable.FooService
example.scannable.FooServiceImpl=org.springframework.stereotype.Component,example.scannable.FooService
example.scannable.ScopedProxyTestBean=example.scannable.FooService
example.scannable.StubFooDao=org.springframework.stereotype.Component
example.scannable.NamedStubDao=org.springframework.stereotype.Component
example.scannable.ServiceInvocationCounter=org.springframework.stereotype.Component
example.scannable.sub.BarComponent=org.springframework.stereotype.Component
```
### debug
- 入口 `org.springframework.context.index.CandidateComponentsIndexLoader.loadIndex`
```java
@Nullable
public static CandidateComponentsIndex loadIndex(@Nullable ClassLoader classLoader) {
ClassLoader classLoaderToUse = classLoader;
if (classLoaderToUse == null) {
classLoaderToUse = CandidateComponentsIndexLoader.class.getClassLoader();
}
return cache.computeIfAbsent(classLoaderToUse, CandidateComponentsIndexLoader::doLoadIndex);
}
```
```java
/**
* 解析 META-INF/spring.components 文件
* @param classLoader
* @return
*/
@Nullable
private static CandidateComponentsIndex doLoadIndex(ClassLoader classLoader) {
if (shouldIgnoreIndex) {
return null;
}
try {
Enumeration<URL> urls = classLoader.getResources(COMPONENTS_RESOURCE_LOCATION);
if (!urls.hasMoreElements()) {
return null;
}
List<Properties> result = new ArrayList<>();
while (urls.hasMoreElements()) {
URL url = urls.nextElement();
// 读取META-INF/spring.components文件转换成map对象
Properties properties = PropertiesLoaderUtils.loadProperties(new UrlResource(url));
result.add(properties);
}
if (logger.isDebugEnabled()) {
logger.debug("Loaded " + result.size() + "] index(es)");
}
int totalCount = result.stream().mapToInt(Properties::size).sum();
// 查看CandidateComponentsIndex方法
return (totalCount > 0 ? new CandidateComponentsIndex(result) : null);
}
catch (IOException ex) {
throw new IllegalStateException("Unable to load indexes from location [" +
COMPONENTS_RESOURCE_LOCATION + "]", ex);
}
}
```
```java
CandidateComponentsIndex(List<Properties> content) {
this.index = parseIndex(content);
}
/**
* 解析 MATE-INF\spring.components 转换成 map
*
* @param content
* @return
*/
private static MultiValueMap<String, Entry> parseIndex(List<Properties> content) {
MultiValueMap<String, Entry> index = new LinkedMultiValueMap<>();
for (Properties entry : content) {
entry.forEach((type, values) -> {
String[] stereotypes = ((String) values).split(",");
for (String stereotype : stereotypes) {
index.add(stereotype, new Entry((String) type));
}
});
}
return index;
}
```
![image-20200115105941265](/images/spring/image-20200115105941265.png)
- 该类给`org.springframework.context.annotation.ClassPathScanningCandidateComponentProvider.findCandidateComponents`提供了帮助
```java
public Set<BeanDefinition> findCandidateComponents(String basePackage) {
// 扫描
/**
* if 测试用例: {@link org.springframework.context.annotation.ClassPathScanningCandidateComponentProviderTests#defaultsWithIndex()}
* 解析 spring.components文件
*/
if (this.componentsIndex != null && indexSupportsIncludeFilters()) {
return addCandidateComponentsFromIndex(this.componentsIndex, basePackage);
}
else {
return scanCandidateComponents(basePackage);
}
}
```

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