public class ExampleBean {
// Number of years to calculate the Ultimate Answer
private int years;
// The Answer to Life, the Universe, and Everything
private String ultimateAnswer;
public ExampleBean(int years, String ultimateAnswer) {
this.years = years;
this.ultimateAnswer = ultimateAnswer;
}
}
public class ExampleBeanWithConstructorProperties {
// Number of years to calculate the Ultimate Answer
private int years;
// The Answer to Life, the Universe, and Everything
private String ultimateAnswer;
@ConstructorProperties({"years", "ultimateAnswer"})
public ExampleBeanWithConstructorProperties(int years, String ultimateAnswer) {
this.years = years;
this.ultimateAnswer = ultimateAnswer;
}
}
基于Setter的注入
Setter注入主要用来无参构造器或者获得对象实例之后才设置对象的属性。下面是Setter的例子：
public class SimpleMovieLister {
// the SimpleMovieLister has a dependency on the MovieFinder
private MovieFinder movieFinder;
// a setter method so that the Spring container can inject a MovieFinder
public void setMovieFinder(MovieFinder movieFinder) {
this.movieFinder = movieFinder;
}
// business logic that actually uses the injected MovieFinder is omitted...
}
package com.flydean.beans;
import lombok.Data;
@Data
public class SimpleMovieLister {
// the SimpleMovieLister has a dependency on the MovieFinder
private MovieFinder movieFinder;
// a setter method so that the Spring container can inject a MovieFinder
public void setMovieFinder(MovieFinder movieFinder) {
this.movieFinder = movieFinder;
}
// business logic that actually uses the injected MovieFinder is omitted...
}
public class CommandManager implements ApplicationContextAware {
private ApplicationContext applicationContext;
public Object process(Map commandState) {
// grab a new instance of the appropriate Command
Command command = createCommand();
// set the state on the (hopefully brand new) Command instance
command.setState(commandState);
return command.execute();
}
protected Command createCommand() {
// notice the Spring API dependency!
return this.applicationContext.getBean("command", Command.class);
}
public void setApplicationContext(
ApplicationContext applicationContext) throws BeansException {
this.applicationContext = applicationContext;
}
}
这种方法并不可取的，因为业务代码和Spring框架产生了耦合。方法注入是Spring IoC 容器的一个高级特性，它可以很好的处理这种情况。
public abstract class CommandManagerB {
public Object process(Map commandState) {
// grab a new instance of the appropriate Command interface
AsyncCommand command = createCommand();
return null;
}
// okay... but where is the implementation of this method?
public abstract AsyncCommand createCommand();
}
这里我们定义了一个抽象类，要查找的方法就是createCommand。返回的对象类，如下：
public class AsyncCommand {
}
下面是XML配置文件：
<!-- a stateful bean deployed as a prototype (non-singleton) -->
<bean id="myCommand" class="com.flydean.beans.AsyncCommand" scope="prototype">
<!-- inject dependencies here as required -->
</bean>
<!-- commandProcessor uses statefulCommandHelper -->
<bean id="commandManager" class="com.flydean.beans.CommandManagerB">
<lookup-method name="createCommand" bean="myCommand"/>
</bean>
public class ReplacementComputeValue implements MethodReplacer {
public Object reimplement(Object o, Method m, Object[] args) throws Throwable {
// get the input value, work with it, and return a computed result
String input = (String) args[0];
return "def";
}
}