Java 如何在 Spring 中定义 List bean？
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/2416056/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
How to define a List bean in Spring?
提问by guerda
I'm using Spring to define stages in my application. It's configured that the necessary class (here called Configurator) is injected with the stages.
Now I need the List of Stages in another class, named LoginBean. The Configuratordoesn't offer access to his List of Stages.
我正在使用 Spring 在我的应用程序中定义阶段。它被配置为必要的类（这里称为Configurator）注入了阶段。
现在我需要另一个名为LoginBean. 在Configurator不提供访问其阶段的名单。
I cannot change the class Configurator.
我不能改变班级Configurator。
My Idea:
Define a new bean called Stages and inject it to Configuratorand LoginBean.
My problem with this idea is that I don't know how to transform this property:
我的想法：
定义一个名为 Stages 的新 bean 并将其注入Configurator和LoginBean。我这个想法的问题是我不知道如何转换这个属性：
<property ...>
<list>
<bean ... >...</bean>
<bean ... >...</bean>
<bean ... >...</bean>
</list>
</property>
into a bean.
成豆。
Something like this does not work:
像这样的东西不起作用：
<bean id="stages" class="java.util.ArrayList">
Can anybody help me with this?
有人可以帮我解决这个问题吗？
采纳答案by simonlord
Import the spring util namespace. Then you can define a list bean as follows:
导入 spring util 命名空间。然后你可以定义一个列表 bean，如下所示：
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:util="http://www.springframework.org/schema/util"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/util
http://www.springframework.org/schema/util/spring-util-2.5.xsd">
<util:list id="myList" value-type="java.lang.String">
<value>foo</value>
<value>bar</value>
</util:list>
The value-type is the generics type to be used, and is optional. You can also specify the list implementation class using the attribute list-class.
value-type 是要使用的泛型类型，并且是可选的。您还可以使用属性指定列表实现类list-class。
回答by stacker
Here is one method:
这是一种方法：
<bean id="stage1" class="Stageclass"/>
<bean id="stage2" class="Stageclass"/>
<bean id="stages" class="java.util.ArrayList">
<constructor-arg>
<list>
<ref bean="stage1" />
<ref bean="stage2" />
</list>
</constructor-arg>
</bean>
回答by Stephen C
I think you may be looking for org.springframework.beans.factory.config.ListFactoryBean.
我想你可能正在寻找org.springframework.beans.factory.config.ListFactoryBean.
You declare a ListFactoryBean instance, providing the list to be instantiated as a property withe a <list>element as its value, and give the bean an idattribute. Then, each time you use the declared idas a refor similar in some other bean declaration, a new copy of the list is instantiated. You can also specify the Listclass to be used.
您声明一个 ListFactoryBean 实例，提供要实例化的列表作为属性<list>，并将元素作为其值，并为 bean 提供一个id属性。然后，每次在其他 bean 声明中使用声明id为 aref或类似的声明时，都会实例化列表的新副本。您还可以指定List要使用的类。
回答by Juan Perez
Use the util namespace, you will be able to register the list as a bean in your application context. You can then reuse the list to inject it in other bean definitions.
使用 util 命名空间，您将能够将列表注册为应用程序上下文中的 bean。然后，您可以重用该列表以将其注入其他 bean 定义中。
回答by haju
Stacker posed a great answer, I would go one step farther to make it more dynamic and use Spring 3 EL Expression.
Stacker 提出了一个很好的答案，我会更进一步使其更具动态性并使用 Spring 3 EL Expression。
<bean id="listBean" class="java.util.ArrayList">
<constructor-arg>
<value>#{springDAOBean.getGenericListFoo()}</value>
</constructor-arg>
</bean>
I was trying to figure out how I could do this with the util:list but couldn't get it work due to conversion errors.
我试图弄清楚如何使用 util:list 执行此操作，但由于转换错误而无法使其正常工作。
回答by Koray Tugay
<bean id="someBean"
class="com.somePackage.SomeClass">
<property name="myList">
<list value-type="com.somePackage.TypeForList">
<ref bean="someBeanInTheList"/>
<ref bean="someOtherBeanInTheList"/>
<ref bean="someThirdBeanInTheList"/>
</list>
</property>
</bean>
And in SomeClass:
在 SomeClass 中：
class SomeClass {
List<TypeForList> myList;
@Required
public void setMyList(List<TypeForList> myList) {
this.myList = myList;
}
}
回答by Jakub Kubrynski
Another option is to use JavaConfig. Assuming that all stages are already registered as spring beans you just have to:
另一种选择是使用 JavaConfig。假设所有阶段都已经注册为 spring bean，你只需要：
@Autowired
private List<Stage> stages;
and spring will automatically inject them into this list. If you need to preserve order (upper solution doesn't do that) you can do it in that way:
spring 会自动将它们注入到这个列表中。如果您需要保留订单（上层解决方案不这样做），您可以这样做：
@Configuration
public class MyConfiguration {
@Autowired
private Stage1 stage1;
@Autowired
private Stage2 stage2;
@Bean
public List<Stage> stages() {
return Lists.newArrayList(stage1, stage2);
}
}
The other solution to preserve order is use a @Orderannotation on beans. Then list will contain beans ordered by ascending annotation value.
另一种保持顺序的解决方案是@Order在 bean 上使用注释。然后列表将包含按升序注释值排序的 bean。
@Bean
@Order(1)
public Stage stage1() {
return new Stage1();
}
@Bean
@Order(2)
public Stage stage2() {
return new Stage2();
}
回答by Jose Alban
As an addition to Jakub's answer, if you plan to use JavaConfig, you can also autowire that way:
作为 Jakub 答案的补充，如果您打算使用 JavaConfig，您还可以通过这种方式自动装配：
import com.google.common.collect.Lists;
import java.util.List;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Bean;
<...>
@Configuration
public class MyConfiguration {
@Bean
public List<Stage> stages(final Stage1 stage1, final Stage2 stage2) {
return Lists.newArrayList(stage1, stage2);
}
}
回答by Slava Babin
And this is how to inject set in some property in Spring:
这是如何在 Spring 的某些属性中注入 set：
<bean id="process"
class="biz.bsoft.processing">
<property name="stages">
<set value-type="biz.bsoft.AbstractStage">
<ref bean="stageReady"/>
<ref bean="stageSteady"/>
<ref bean="stageGo"/>
</set>
</property>
</bean>
回答by RaM PrabU
<bean id="student1" class="com.spring.assin2.Student">
<property name="name" value="ram"></property>
<property name="id" value="1"></property>
<property name="listTest">
<list value-type="java.util.List">
<ref bean="test1"/>
<ref bean="test2"/>
</list>
</property>
</bean>
define those beans(test1,test2) afterwards :)
之后定义这些 bean(test1,test2) :)
