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@ComponentScan 详解

unadlib 2022-10-25 阅读 59


@ComponentScan 的作用就是根据定义的扫描路径,把符合扫描规则的类装配到spring容器中,注解定义如下。

 

@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.TYPE})
@Documented
@Repeatable(ComponentScans.class)
public @interface ComponentScan {
@AliasFor("basePackages")
String[] value() default {};

@AliasFor("value")
String[] basePackages() default {};

Class<?>[] basePackageClasses() default {};

Class<? extends BeanNameGenerator> nameGenerator() default BeanNameGenerator.class;

Class<? extends ScopeMetadataResolver> scopeResolver() default AnnotationScopeMetadataResolver.class;

ScopedProxyMode scopedProxy() default ScopedProxyMode.DEFAULT;

String resourcePattern() default "**/*.class";

boolean useDefaultFilters() default true;

ComponentScan.Filter[] includeFilters() default {};

ComponentScan.Filter[] excludeFilters() default {};

boolean lazyInit() default false;

@Retention(RetentionPolicy.RUNTIME)
@Target({})
public @interface Filter {
FilterType type() default FilterType.ANNOTATION;

@AliasFor("classes")
Class<?>[] value() default {};

@AliasFor("value")
Class<?>[] classes() default {};

String[] pattern() default {};
}
}

basePackages与value:  用于指定包的路径,进行扫描

basePackageClasses: 用于指定某个类的包的路径进行扫描

nameGenerator: bean的名称的生成器

useDefaultFilters: 是否开启对@Component,@Repository,@Service,@Controller的类进行检测

includeFilters: 包含的过滤条件

            FilterType.ANNOTATION:按照注解过滤

            FilterType.ASSIGNABLE_TYPE:按照给定的类型

            FilterType.ASPECTJ:使用ASPECTJ表达式

            FilterType.REGEX:正则

            FilterType.CUSTOM:自定义规则

excludeFilters: 排除的过滤条件,用法和includeFilters一样

 

我的工程结构如下,测试对controller和service的扫描,其中HelloController没有加@Controller等任何注解,就是一个普通类。

@ComponentScan 详解_sed

 

修改配置类如下:应用默认的过滤器,扫描service包:

@Configuration
@ComponentScan(value = "com.xhx.spring.service",
useDefaultFilters = true
)
public class MyConfig {
}

系统注入了两个service进去

@ComponentScan 详解_sed_02

 

改成如下所示:HelloController所在的包的类也被扫描了进去

@Configuration
@ComponentScan(value = "com.xhx.spring.service",
useDefaultFilters = true,
basePackageClasses = HelloController.class
)
public class MyConfig {
}

系统中会注入下面就给类

@ComponentScan 详解_sed_03

 

把默认的过滤器关掉,扫描带Controller注解的。

@Configuration
@ComponentScan(value = "com.xhx.spring",
useDefaultFilters = false,
includeFilters = {
@ComponentScan.Filter(type = FilterType.ANNOTATION,classes = {Controller.class})
}
)
public class MyConfig {
}

@ComponentScan 详解_spring_04

 

按照类的类型扫描,虽然HelloController没有加注解,但是被注入到了spring容器中

@Configuration
@ComponentScan(value = "com.xhx.spring",
useDefaultFilters = false,
includeFilters = {
@ComponentScan.Filter(type = FilterType.ASSIGNABLE_TYPE,classes = {HelloController.class})
}
)
public class MyConfig {
}

@ComponentScan 详解_spring_05

 

自定义扫描过滤器

package com.xhx.spring.componentscan.config;

import org.springframework.core.type.classreading.MetadataReader;
import org.springframework.core.type.classreading.MetadataReaderFactory;
import org.springframework.core.type.filter.TypeFilter;

import java.io.IOException;

/**
* xuhaixing
* 2018/9/18 23:07
**/
public class MyTypeFilter implements TypeFilter {
@Override
public boolean match(MetadataReader metadataReader, MetadataReaderFactory metadataReaderFactory) throws IOException {
String className = metadataReader.getClassMetadata().getClassName();
if(className.contains("Controller")){
return true;
}
return false;
}
}

修改配置类

@Configuration
@ComponentScan(value = "com.xhx.spring",
useDefaultFilters = false,
includeFilters = {
@ComponentScan.Filter(type = FilterType.CUSTOM,classes = {MyTypeFilter.class})
}
)
public class MyConfig {
}

输出结果:

@ComponentScan 详解_spring_06

 

输出spring容器中的bean的测试类:只过滤输出了名字中含有hello的类。

package com.xhx.spring.componentscan;

import com.xhx.spring.componentscan.config.MyConfig;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.test.context.junit4.SpringRunner;

import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;

@RunWith(SpringRunner.class)
@SpringBootTest
public class ComponentScanApplicationTests {

@Test
public void testLoads() {
AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(MyConfig.class);
List<String> hello = Arrays.stream(context.getBeanDefinitionNames()).collect(Collectors.toList());
hello.stream().filter(name->name.contains("hello")).peek(System.out::println).count();
}

}

 

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@ComponentScan 详解_spring_07

 

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