【Spring Framework】spring管理自己new的对象
使用AutowireCapableBeanFactory手动注入
使用.newInstance();创建对象的话，如果其他对象都使用Spring Autowired，还需要手动创建所有依赖的Bean:
private @Autowired AutowireCapableBeanFactory beanFactory;
public void process() {
MyBean obj = new MyBean();
beanFactory.autowireBean(obj);
// obj will now have its dependencies autowired.
}
例如策略工厂中可以
private @Autowired AutowireCapableBeanFactory beanFactory;
/**
* 使用策略工厂获取具体策略实现
* @param code
* @return
*/
public PayStrategy getPayStrategy(String code) {
String className = PayEnumStrategy.getClassNameByCode(code);
try {
PayStrategy str = (PayStrategy) Class.forName(className).getDeclaredConstructor().newInstance();
beanFactory.autowireBean(str);
return str;
} catch (InstantiationException |
NoSuchMethodException |
ClassNotFoundException |
IllegalAccessException |
InvocationTargetException e) {
e.printStackTrace();
}
return null;
}
但是这种方式只有对field注入方式才有用。
使用Map<String,?> 自动注入
先附上如下的代码：
public interface TalkService {
void talk(String content);
}
@Service(value = "withSisterTalkService")
public class WithSisterTalkService implements TalkService {
@Override
public void talk(String content) {
System.out.println(this.getClass().getName() + ":" + content);
}
}
@Service(value = "withGirlFriendTalkService")
public class WithGirlFriendTalkService implements TalkService {
@Override
public void talk(String content) {
System.out.println(this.getClass().getName() + ":" + content);
}
}
@Service
public class TalkServiceStrategyContext implements TalkService {
private Map<String, TalkService> strategyMap = new ConcurrentHashMap<>();
@Autowired
public TalkServiceStrategyContext(Map<String, TalkService> strategyMap) {
this.strategyMap.clear();
this.strategyMap.putAll(strategyMap);
}
@Override
public void talk(String content) {
}
}
注意，这里必须是Map<String, TalkService>类型！
@Autowired
private Map<String, TalkService> talkServiceMap;
@GetMapping(value = "doTest")
public String doTest() {
Set<String> strings = talkServiceMap.keySet();
for (String string : strings) {
System.out.println(string + ":" + talkServiceMap.get(string).toString());
}
return this.getClass().getName();
}
其访问测试controller后，打印的信息如下：
talkServiceStrategyContext:com.haiyang.onlinejava.complier.service.impl.TalkServiceStrategyContext@2f0b1419
withGirlFriendTalkService:com.haiyang.onlinejava.complier.service.impl.WithGirlFriendTalkService@1cf19a02
withSisterTalkService:com.haiyang.onlinejava.complier.service.impl.WithSisterTalkService@1ef3c76d
看了后感觉很奇怪，在上方只定义了一个map<String,TalkService>的map,居然它就能自动找到实现了TalkService的所有bean,并将service的beanName作为了key，感觉还是牛逼啊，spring的注解居然还能这样用。
然后简单看了下Autowired的源码，其javaDoc文档里也有说明：
package org.springframework.beans.factory.annotation;
import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
/**
* Marks a constructor, field, setter method or config method as to be
* autowired by Spring's dependency injection facilities.
*
* <p>Only one constructor (at max) of any given bean class may carry this
* annotation, indicating the constructor to autowire when used as a Spring
* bean. Such a constructor does not have to be public.
*
* <p>Fields are injected right after construction of a bean, before any
* config methods are invoked. Such a config field does not have to be public.
*
* <p>Config methods may have an arbitrary name and any number of arguments;
* each of those arguments will be autowired with a matching bean in the
* Spring container. Bean property setter methods are effectively just
* a special case of such a general config method. Such config methods
* do not have to be public.
*
* <p>In the case of multiple argument methods, the 'required' parameter is
* applicable for all arguments.
*
* <p>In case of a {@link java.util.Collection} or {@link java.util.Map}
* dependency type, the container will autowire all beans matching the
* declared value type. In case of a Map, the keys must be declared as
* type String and will be resolved to the corresponding bean names.
*
* <p>Note that actual injection is performed through a
* {@link org.springframework.beans.factory.config.BeanPostProcessor
* BeanPostProcessor} which in turn means that you <em>cannot</em>
* use {@code @Autowired} to inject references into
* {@link org.springframework.beans.factory.config.BeanPostProcessor
* BeanPostProcessor} or
* {@link org.springframework.beans.factory.config.BeanFactoryPostProcessor BeanFactoryPostProcessor}
* types. Please consult the javadoc for the {@link AutowiredAnnotationBeanPostProcessor}
* class (which, by default, checks for the presence of this annotation).
*
* @author Juergen Hoeller
* @author Mark Fisher
* @since 2.5
* @see AutowiredAnnotationBeanPostProcessor
* @see Qualifier
* @see Value
*/
@Target({ElementType.CONSTRUCTOR, ElementType.METHOD, ElementType.PARAMETER, ElementType.FIELD, ElementType.ANNOTATION_TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Autowired {
/**
* Declares whether the annotated dependency is required.
* <p>Defaults to {@code true}.
*/
boolean required() default true;
}
关注这句：
In case of a java.util.Collection or java.util.Map dependency type, the container will autowire all beans matching the declared value type. In case of a Map, the keys must be declared as type String and will be resolved to the corresponding bean names.
它大致是说Autowired当使用在Collection里时，会将所申明类的所有实现类都放在那个指定的Collection里；
如果Autowired和map使用的话呢，它将它bean的名称作为key,所有的bean作为value.
使用Set<?>自动注入
如果不想使用bean的名字作为map的Key的话，我们可以自定义寻址方式，自动注入时候使用Set<?>：
public interface Strategy {
void doStuff();
StrategyName getStrategyName();
}
public enum StrategyName {
StrategyA,
StrategyB,
StrategyC
}
@Component
public class StrategyA implements Strategy{
@Override
public void doStuff() {
//implement algorithm A here
}
@Override
public StrategyName getStrategyName() {
return StrategyName.StrategyA;
}
}
@Component
public class StrategyB implements Strategy{
@Override
public void doStuff() {
//implement algorithm B here
}
@Override
public StrategyName getStrategyName() {
return StrategyName.StrategyB;
}
}
@Component
public class StrategyC implements Strategy{
@Override
public void doStuff() {
}
@Override
public StrategyName getStrategyName() {
return StrategyName.StrategyC;
}
}
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
import org.springframework.stereotype.Component;
@Component
public class StrategyFactory {
private Map<StrategyName, Strategy> strategies;
@Autowired
public StrategyFactory(Set<Strategy> strategySet) {
createStrategy(strategySet);
}
public Strategy findStrategy(StrategyName strategyName) {
return strategies.get(strategyName);
}
private void createStrategy(Set<Strategy> strategySet) {
strategies = new HashMap<StrategyName, Strategy>();
strategySet.forEach(
strategy ->strategies.put(strategy.getStrategyName(), strategy));
}
}
Now we can inject StrategyFactory using @Autowired annotation. Here is the sample code using our StrategyFactory.
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
@Service
public class SomeService {
@Autowired
private StrategyFactory strategyFactory;
public void findSome(){
// Now get the strategy by passing the name
Strategy strategy = strategyFactory.findStrategy(StrategyName.StrategyA);
// you can now call the methods defined in strategy.
strategy.doStuff();
}
}
