How to implement SpringBoot2 dynamic @Value

The specific implementation steps are divided into the following steps

1. Obtain the beans annotated with @Value through BeanPostProcessor and store them in the map

2. Dynamically modify the beans in the map The value of the field

Get the bean

First write a class to implement the BeanPostProcessor interface, and only need to use one of its functions. It can be implemented both before and after, and it does not affect the final use, because we only need instances of beans.

Let’s take a look at the specific implementation code

package com.allen.apollo;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.beans.factory.config.BeanPostProcessor;
import org.springframework.context.annotation.Configuration;
import org.springframework.util.ReflectionUtils;
import java.lang.reflect.Field;
import java.util.LinkedList;
import java.util.List;
import java.util.Set;
@Configuration
public class SpringValueProcessor implements BeanPostProcessor {
    private final PlaceholderHelper placeholderHelper = new PlaceholderHelper();
    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        if (beanName.equals("springValueController")) {
            Class obj = bean.getClass();
            List fields = findAllField(obj);
            for (Field field : fields) {
                Value value = field.getAnnotation(Value.class);
                if (value != null) {
                    Set keys = placeholderHelper.extractPlaceholderKeys(value.value());
                    for (String key : keys) {
                        SpringValue springValue = new SpringValue(key, value.value(), bean, beanName, field, false);
                        SpringValueCacheMap.map.put(key, springValue);
                    }
                }
            }
        }
        return bean;
    }
    private List findAllField(Class clazz) {
        final List res = new LinkedList<>();
        ReflectionUtils.doWithFields(clazz, new ReflectionUtils.FieldCallback() {
            @Override
            public void doWith(Field field) throws IllegalArgumentException, IllegalAccessException {
                res.add(field);
            }
        });
        return res;
    }
}

In the above code, we have already obtained the instance bean of SpringValueController and stored it in the map. Let’s take a look at the test code

  /**
   * cache  field,存储bean 字段
   */
package com.allen.apollo;
import com.google.common.collect.LinkedListMultimap;
import com.google.common.collect.Multimap;
public class SpringValueCacheMap {
    public static final Multimap map = LinkedListMultimap.create();
}

 package com.allen.apollo;
import java.lang.ref.WeakReference;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Type;
import org.springframework.core.MethodParameter;
public class SpringValue {
    private MethodParameter methodParameter;
    private Field field;
    private WeakReference