我想拥有 Set<LocationResolver>
像这样在 Spring 上下文中定义:
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:util="http://www.springframework.org/schema/util"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.0.xsd
http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-4.0.xsd
http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd">
<context:component-scan base-package="org.foo"/>
<!-- Artifact LocationResolvers -->
<bean id="fsLocationResolver" class="org.foo.storage.resolvers.FSLocationResolver" />
<bean id="memoryLocationResolver" class="org.foo.storage.resolvers.InMemoryLocationResolver" />
<!-- The Set<LocationResolver> -->
<util:set id="resolvers" value-type="org.foo.storage.resolvers.LocationResolver">
<ref bean="memoryLocationResolver"/>
<ref bean="fsLocationResolver"/>
</util:set>
<bean id="configurationManager"
class="org.foo.configuration.ConfigurationManager"
init-method="init">
</bean>
<bean id="artifactResolutionService" class="org.foo.resolvers.ArtifactResolutionService">
<property name="resolvers" ref="resolvers"/>
</bean>
</beans>
我的 ArtifactResolutionService
:
package org.foo.storage.resolvers;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Set;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
@Component
public class ArtifactResolutionService
{
@Resource(name = "resolvers")
private Set<LocationResolver> resolvers;
public Set<LocationResolver> getResolvers()
{
return resolvers;
}
public void setResolvers(Set<LocationResolver> resolvers)
{
this.resolvers = resolvers;
}
}
我的 ConfigurationManager
类:
package org.foo.configuration;
import org.foo.resource.ConfigurationResourceResolver;
import org.foo.storage.Storage;
import org.foo.storage.resolvers.ArtifactResolutionService;
import org.foo.storage.resolvers.LocationResolver;
import org.foo.xml.parsers.ConfigurationParser;
import java.io.IOException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Scope;
import org.springframework.core.io.Resource;
import org.springframework.stereotype.Component;
@Component
@Scope ("singleton")
public class ConfigurationManager
{
private static final Logger logger = LoggerFactory.getLogger(ConfigurationManager.class);
private String configurationPath;
private Configuration configuration;
@Autowired
private ConfigurationResourceResolver configurationResourceResolver;
@Autowired
private ArtifactResolutionService artifactResolutionService;
public ConfigurationManager()
{
}
public void init()
throws IOException
{
Resource resource = configurationResourceResolver.getConfigurationResource("etc/configuration.xml",
"repository.config.xml",
"etc/configuration.xml");
logger.info("Loading configuration from " + resource.toString() + "...");
ConfigurationParser parser = new ConfigurationParser();
configuration = parser.parse(resource.getInputStream());
configuration.setResource(resource);
dump();
}
public void dump()
{
System.out.println("Configuration version: " + configuration.getVersion());
System.out.println("Listening on port: " + configuration.getPort());
System.out.println("Loading storages...");
for (String storageKey : configuration.getStorages().keySet())
{
System.out.println(" -> Storage: " + storageKey);
Storage storage = configuration.getStorages().get(storageKey);
for (String repositoryKey : storage.getRepositories().keySet())
{
System.out.println(" -> Repository: " + repositoryKey);
}
}
//
// This throws a NullPointerException, as the resolvers are null.
//
System.out.println("Loading resolvers...");
for (LocationResolver resolver : artifactResolutionService.getResolvers())
{
System.out.println(" -> " + resolver.getClass());
}
}
public void storeConfiguration(Configuration configuration, String file)
throws IOException
{
ConfigurationParser parser = new ConfigurationParser();
parser.store(configuration, file);
}
public Configuration getConfiguration()
{
return configuration;
}
public void setConfiguration(Configuration configuration)
{
this.configuration = configuration;
}
public String getConfigurationPath()
{
return configurationPath;
}
public void setConfigurationPath(String configurationPath)
{
this.configurationPath = configurationPath;
}
public ArtifactResolutionService getArtifactResolutionService()
{
return artifactResolutionService;
}
public void setArtifactResolutionService(ArtifactResolutionService artifactResolutionService)
{
this.artifactResolutionService = artifactResolutionService;
}
}
resolvers
, 然而,最终是 null
我似乎无法弄清楚这一点。有什么明显的地方我做错了吗?
非常感谢!
最佳答案
有两件事值得警惕。
首先你有这个
<context:component-scan base-package="org.foo"/>
与
package org.foo.storage.resolvers;
@Component
public class ArtifactResolutionService
这意味着您正在隐式创建一个ArtifactResolutionService
bean 。你还有
<bean id="artifactResolutionService" class="org.foo.resolvers.ArtifactResolutionService">
<property name="resolvers" ref="resolvers"/>
</bean>
显式创建第二个 ArtifactResolutionService
bean(bean 定义可能会相互覆盖,因为它们具有相同的 id)。在这两种情况下,您都有办法注入(inject) Set
解析器。一个是 @Autowired
, 另一个是 <property>
.
其次,你的Spring配置不可能注入(inject)null
在托管 bean 中。
您可能在 bean 的生命周期中尝试在错误的时间使用该字段,此时该字段尚未被注入(inject)。
看来你有循环依赖。 Spring 尝试注入(inject) ConfigurationManager
进入 LocationResolver
之一在它 Autowiring 它的字段之前。为此,它需要调用 init-method
.
注意带注解配置,我信这个
@Autowired
private Set<LocationResolver> resolvers;
实际上会拾取所有 LocationResolver
bean ,不是你的Set
bean 在这里定义
<!-- The Set<LocationResolver> -->
<util:set id="resolvers" value-type="org.foo.storage.resolvers.LocationResolver">
<ref bean="memoryLocationResolver"/>
<ref bean="fsLocationResolver"/>
</util:set>
如果你想要 Set
bean,我会使用 @Resource
@Resource(name = "resolvers")
private Set<LocationResolver> resolvers;
关于java - Autowiring 定义为 <util :set> in Spring 的集合,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/22463052/