springboot BeanFactoryPostProcessor与BeanPostProcessor

末蓝、 2022-09-02 11:35 178阅读 0赞

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## springboot BeanFactoryPostProcessor与BeanPostProcessor ##

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**相关类与接口**

**BeanFactoryPostProcessor：对象实例化前调用，可修改beanDefinition**

public interface BeanFactoryPostProcessor {
        void postProcessBeanFactory(ConfigurableListableBeanFactory var1) throws BeansException;
    }

**ConfigurableListableBeanFactory**

public interface ConfigurableListableBeanFactory extends ListableBeanFactory, AutowireCapableBeanFactory, ConfigurableBeanFactory {
    
        BeanDefinition getBeanDefinition(String var1) throws NoSuchBeanDefinitionException;
        Iterator<String> getBeanNamesIterator();
    
        boolean isConfigurationFrozen();
        boolean isAutowireCandidate(String var1, DependencyDescriptor var2) throws NoSuchBeanDefinitionException;
    
        void ignoreDependencyType(Class<?> var1);
        void ignoreDependencyInterface(Class<?> var1);
        void registerResolvableDependency(Class<?> var1, @Nullable Object var2);
    
        void clearMetadataCache();
        void freezeConfiguration();
        void preInstantiateSingletons() throws BeansException;
    }

**BeanDefinition**

public interface BeanDefinition extends AttributeAccessor, BeanMetadataElement {
    
        String SCOPE_SINGLETON = "singleton";
        String SCOPE_PROTOTYPE = "prototype";
        int ROLE_APPLICATION = 0;
        int ROLE_SUPPORT = 1;
        int ROLE_INFRASTRUCTURE = 2;
    
        void setRole(int var1);
        void setScope(@Nullable String var1);
        void setDependsOn(@Nullable String... var1);
        void setDescription(@Nullable String var1);
    
        int getRole();
        String getScope();
        String[] getDependsOn();
        String getDescription();
    
    
        void setParentName(@Nullable String var1);
        void setBeanClassName(@Nullable String var1);
        void setFactoryBeanName(@Nullable String var1);
        void setFactoryMethodName(@Nullable String var1);
        void setInitMethodName(@Nullable String var1);
        void setDestroyMethodName(@Nullable String var1);
    
    
        String getParentName();
        String getBeanClassName();
        String getFactoryBeanName();
        String getFactoryMethodName();
        String getInitMethodName();
        String getDestroyMethodName();
    
    
        void setPrimary(boolean var1);
        void setLazyInit(boolean var1);
        void setAutowireCandidate(boolean var1);
    
        boolean isPrimary();
        boolean isLazyInit();
        boolean isAutowireCandidate();
    
        boolean isSingleton();
        boolean isPrototype();
        boolean isAbstract();
    
    
        ConstructorArgumentValues getConstructorArgumentValues();
        default boolean hasConstructorArgumentValues() {
            return !this.getConstructorArgumentValues().isEmpty();
        }
    
        MutablePropertyValues getPropertyValues();
        default boolean hasPropertyValues() {
            return !this.getPropertyValues().isEmpty();
        }
    
    
        ResolvableType getResolvableType();
        String getResourceDescription();
        BeanDefinition getOriginatingBeanDefinition();
    }

**AttributeAccessor**

public interface AttributeAccessor {
    
        String[] attributeNames();
    
        boolean hasAttribute(String var1);
        void setAttribute(String var1, @Nullable Object var2);
        Object getAttribute(String var1);
        Object removeAttribute(String var1);
    
        default <T> T computeAttribute(String name, Function<String, T> computeFunction) {
            Assert.notNull(name, "Name must not be null");
            Assert.notNull(computeFunction, "Compute function must not be null");
            Object value = this.getAttribute(name);
            if (value == null) {
                value = computeFunction.apply(name);
                Assert.state(value != null, () -> {
                    return String.format("Compute function must not return null for attribute named '%s'", name);
                });
                this.setAttribute(name, value);
            }
    
            return value;
        }
    
    }

**BeanPostProcessor：对象初始化前后调用**

public interface BeanPostProcessor {
        @Nullable
        default Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
            return bean;
        }                   //对象初始化前调用
    
        @Nullable
        default Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
            return bean;
        }                   //对象初始化后调用
    }

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**示例**

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**pojo 层**

**Person**

@Data
    public class Person {
    
        private String name;
        private Integer age;
    }

**Student**

@Data
    public class Student {
    
        private String name;
        private Integer age;
    }

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**config 层**

**DataConfig**

@Configuration
    public class DataConfig {
    
        @Bean("person")
        public Person initPerson(){
            Person person=new Person();
            person.setName("海贼王");
            person.setAge(20);
    
            return person;
        }
    
        @Bean("student")
        public Student initStudent(){
            Student student=new Student();
            student.setName("瓜田李下");
            student.setAge(20);
    
            return student;
        }
    }

**CustomBeanFactoryPostProcessor**

@Component
    public class CustomBeanFactoryPostProcessor implements BeanFactoryPostProcessor {
    
        @Override
        public void postProcessBeanFactory(ConfigurableListableBeanFactory configurableListableBeanFactory) throws BeansException {
            BeanDefinition beanDefinition=configurableListableBeanFactory.getBeanDefinition("person");
            System.out.println(beanDefinition);
    
            String[] s=configurableListableBeanFactory.getBeanDefinitionNames();
            List<String> list=Arrays.asList(s);
            if (list.contains("person")){
                System.out.println(true);
            }
    
            System.out.println(beanDefinition.hasPropertyValues());
            MutablePropertyValues propertyValues=beanDefinition.getPropertyValues();
            System.out.println(propertyValues);
            PropertyValue[] p=propertyValues.getPropertyValues();
            System.out.println(p.length);
    
            System.out.println(propertyValues.contains("name"));
            propertyValues.removePropertyValue("name");
            propertyValues.add("name","瓜田李下");
            System.out.println(propertyValues);
        }  //添加的name属性，在populateBean()时设置,替换原来的属性("海贼王")
    }

**CustomBeanPostProcessor：****对所有bean初始化前后都做处理**

@Component
    public class CustomBeanPostProcessor implements BeanPostProcessor {
    
        @Override
        public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
            if (bean instanceof Student || bean instanceof Person){
                System.out.println(beanName+"调用postProcessBeforeInitialization");
                System.out.println(bean);
            }
    
            return BeanPostProcessor.super.postProcessBeforeInitialization(bean, beanName);
        }
    
        @Override
        public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
            if (bean instanceof Student || bean instanceof Person){
                System.out.println(beanName+"调用postProcessBeforeInitialization");
                System.out.println(bean+"\n");
            }
    
            return BeanPostProcessor.super.postProcessAfterInitialization(bean, beanName);
        }
    }

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**controller 层**

**HelloController**

@RestController
    public class HelloController {
    
        @Resource
        private Person person;
    
        @Resource
        private Student student;
    
        @RequestMapping("/hello")
        public String hello(){
            System.out.println(person);
            System.out.println(student);
    
            return "success";
        }
    }

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**测试输出**

**启动后，控制台输出**

true
    false
    PropertyValues: length=0
    0
    false
    PropertyValues: length=1; bean property 'name'
    2021-08-04 22:52:39.308  INFO 2380 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with port(s): 8080 (http)
    2021-08-04 22:52:39.318  INFO 2380 --- [           main] o.apache.catalina.core.StandardService   : Starting service [Tomcat]
    2021-08-04 22:52:39.318  INFO 2380 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet engine: [Apache Tomcat/9.0.50]
    2021-08-04 22:52:39.322  INFO 2380 --- [           main] o.a.catalina.core.AprLifecycleListener   : An older version [1.2.23] of the Apache Tomcat Native library is installed, while Tomcat recommends a minimum version of [1.2.30]
    2021-08-04 22:52:39.323  INFO 2380 --- [           main] o.a.catalina.core.AprLifecycleListener   : Loaded Apache Tomcat Native library [1.2.23] using APR version [1.7.0].
    2021-08-04 22:52:39.323  INFO 2380 --- [           main] o.a.catalina.core.AprLifecycleListener   : APR capabilities: IPv6 [true], sendfile [true], accept filters [false], random [true], UDS [false].
    2021-08-04 22:52:39.323  INFO 2380 --- [           main] o.a.catalina.core.AprLifecycleListener   : APR/OpenSSL configuration: useAprConnector [false], useOpenSSL [true]
    2021-08-04 22:52:39.329  INFO 2380 --- [           main] o.a.catalina.core.AprLifecycleListener   : OpenSSL successfully initialized [OpenSSL 1.1.1c  28 May 2019]
    2021-08-04 22:52:39.481  INFO 2380 --- [           main] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
    2021-08-04 22:52:39.482  INFO 2380 --- [           main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 1145 ms
    person调用postProcessBeforeInitialization
    Person(name=瓜田李下, age=20)
    person调用postProcessBeforeInitialization
    Person(name=瓜田李下, age=20)
    
    //populateBean()后，name属性已经修改为瓜田李下
    //postProcessBeforeInitialization、
    //postProcessBeforeInitialization均在populateBean之后调用
    
    
    student调用postProcessBeforeInitialization
    Student(name=瓜田李下, age=20)
    student调用postProcessBeforeInitialization
    Student(name=瓜田李下, age=20)

**localhost:8080/hello，控制台输出：**

2021-08-04 23:01:35.354  INFO 12920 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : Initializing Servlet 'dispatcherServlet'
    2021-08-04 23:01:35.354  INFO 12920 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : Completed initialization in 0 ms
    Person(name=瓜田李下, age=20)
    Student(name=瓜田李下, age=20)