Springboot項目實現將類從@ComponentScan中排除

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將類從@ComponentScan中排除

問題描述

最近在學習SpringCloud的Ribbon，在使用

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

為服務指定負載均衡策略的時候，根據Ribbon官方文檔介紹，自定義的Ribbon配置類不允許被Springboot的**@ComponentScan**註解掃描到，所以需要將自定義的配置類RibbonConfig從在Springboot自動註入的范圍內排除

方案一

我們都知道，Springboot的**@SpringBootApplication**會自動掃描本類所在包下的所有類和子類，所以隻需要將RibbonConfig定義在Springboot啟動類所在包外面即可

方案二

通過在啟動類中添加

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

通過FilterType.ASSIGNABLE_TYPE來指定要排除的類

如果需要排除的類太多瞭這個就很麻煩

方案三

通過自定義註解實現

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

與方案二不同的是，這裡用的是FilterType.ANNOTATION

方案四

通過實現TypeFilter類來自定義過濾器

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

此處給出的就是**@SpringbootApplication中的實現方式，通過FilterType.CUSTOM**來根據自動一過濾器來排除bean

最後貼出枚舉類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 詳解

@ComponentScan 的作用就是根據定義的掃描路徑，把符合掃描規則的類裝配到spring容器中，註解定義如下。

 
@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與value: 用於指定包的路徑，進行掃描
  • basePackageClasses: 用於指定某個類的包的路徑進行掃描
  • nameGenerator: bean的名稱的生成器
  • useDefaultFilters: 是否開啟對@Component，@Repository，@Service，@Controller的類進行檢測
  • includeFilters: 包含的過濾條件

FilterType.ANNOTATION：按照註解過濾

FilterType.ASSIGNABLE_TYPE：按照給定的類型

FilterType.ASPECTJ：使用ASPECTJ表達式

FilterType.REGEX：正則

FilterType.CUSTOM：自定義規則

  • excludeFilters: 排除的過濾條件，用法和includeFilters一樣

我的工程結構如下，測試對controller和service的掃描，其中HelloController沒有加@Controller等任何註解，就是一個普通類。

修改配置類如下：應用默認的過濾器，掃描service包：

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

系統註入瞭兩個service進去

改成如下所示：HelloController所在的包的類也被掃描瞭進去

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

系統中會註入下面就給類

把默認的過濾器關掉，掃描帶Controller註解的。

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

按照類的類型掃描，雖然HelloController沒有加註解，但是被註入到瞭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 {
}

自定義掃描過濾器

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;
    }
}

修改配置類

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

輸出結果：

輸出spring容器中的bean的測試類：隻過濾輸出瞭名字中含有hello的類。

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();
    } 
}

以上為個人經驗，希望能給大傢一個參考，也希望大傢多多支持WalkonNet。

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