Springboot项目实现将类从@ComponentScan中排除

目录

• 将类从@ComponentScan中排除
• 问题描述
• 方案一
• 方案二
• 方案三
• 方案四
• @ComponentScan 详解

将类从@ComponentScan中排除

问题描述

最近在学习SpringCloud的Ribbon，在使用

@RibbonClient(name = "SPRINGCLOUD-P-DEPT",
   configuration = RibbonConfig.class)

为服务指定负载均衡策略的时候，根据Ribbon官方文档介绍，自定义的Ribbon配置类不允许被Springboot的**@ComponentScan**注解扫描到，所以需要将自定义的配置类RibbonConfig从在Springboot自动注入的范围内排除

方案一

我们都知道，Springboot的**@SpringBootApplication**会自动扫描本类所在包下的所有类和子类，所以只需要将RibbonConfig定义在Springboot启动类所在包外面即可

方案二

通过在启动类中添加

@ComponentScan(excludeFilters = @ComponentScan.Filter(
  type = FilterType.ASSIGNABLE_TYPE,
  classes = RibbonConfig.class))

通过FilterType.ASSIGNABLE_TYPE来指定要排除的类

如果需要排除的类太多了这个就很麻烦

方案三

通过自定义注解实现

@ComponentScan(excludeFilters = @ComponentScan.Filter(
  type = FilterType.ANNOTATION,
  classes = ScanIgnore.class))

与方案二不同的是，这里用的是FilterType.ANNOTATION

方案四

通过实现TypeFilter类来自定义过滤器

@ComponentScan(excludeFilters = {
 @Filter(
  type = FilterType.CUSTOM,
  classes = TypeExcludeFilter.class),
 @Filter(
  type = FilterType.CUSTOM,
  classes = AutoConfigurationExcludeFilter.class) })

此处给出的就是**@SpringbootApplication中的实现方式，通过FilterType.CUSTOM**来根据自动一过滤器来排除bean

最后贴出枚举类FilterType：

/*
 * Copyright 2002-2013 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.springframework.context.annotation;
/**
 * Enumeration of the type filters that may be used in conjunction with
 * {@link ComponentScan @ComponentScan}.
 *
 * @author Mark Fisher
 * @author Juergen Hoeller
 * @author Chris Beams
 * @since 2.5
 * @see ComponentScan
 * @see ComponentScan#includeFilters()
 * @see ComponentScan#excludeFilters()
 * @see org.springframework.core.type.filter.TypeFilter
 */
public enum FilterType {
 /**
  * Filter candidates marked with a given annotation.
  * @see org.springframework.core.type.filter.AnnotationTypeFilter
  */
 ANNOTATION,
 /**
  * Filter candidates assignable to a given type.
  * @see org.springframework.core.type.filter.AssignableTypeFilter
  */
 ASSIGNABLE_TYPE,
 /**
  * Filter candidates matching a given AspectJ type pattern expression.
  * @see org.springframework.core.type.filter.AspectJTypeFilter
  */
 ASPECTJ,
 /**
  * Filter candidates matching a given regex pattern.
  * @see org.springframework.core.type.filter.RegexPatternTypeFilter
  */
 REGEX,
 /** Filter candidates using a given custom
  * {@link org.springframework.core.type.filter.TypeFilter} implementation.
  */
 CUSTOM
}

@ComponentScan 详解

@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。

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

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

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 {
}

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 {
}

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：

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();
    }
}

以上为个人经验，希望能给大家一个参考，也希望大家多多支持我们。