解決自定義securityMetadataSource不能使用依賴注入的問題，nullpointer問題，空指標問題
spring3,spring security,MySecurityMetadataSource,自定義securityMetadataSource,依賴注入,註解,注入,空指標異常,nullpointer,service
解決的問題，nullpointer問題，空指標問題我在配置spring3和Security3 的時候為了從資料庫管理資源，自定義了securityMetadataSource，但是在類中使用依賴注入的話，載入applicationContext-security.xml的時候，會丟擲使用依賴注入的那一行物件為null，是什麼原因？也就是說提示依賴注入resourcesServiceImpl
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name'mySecurityMetadataSource' defined in file [E:\Program Files\Apache SoftwareFoundation\Tomcat6.0\webapps\testSpringSecure\WEB-INF\classes\com\test\security\MySecurityMetadataSource.class]:Instantiation of bean failed; nested exception is
atorg.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(
atorg.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:943)
atorg.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:485)
atorg.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:456)
atorg.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:294)
atorg.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:225)
atorg.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:291)
atorg.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:193)
atorg.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveReference(BeanDefinitionValueResolver.java:322)
...53 more
Caused by: org.springframework.beans.BeanInstantiationException: Could not instantiate bean class[com.test.security.MySecurityMetadataSource]: Constructor threw exception;nested exception is java.lang.NullPointerException
atorg.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:162)
atorg.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:76)
atorg.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:990)
...61 more
Caused by: java.lang.NullPointerException
atcom.test.security.MySecurityMetadataSource.loadResourceDefine(MySecurityMetadataSource.java:81)
atcom.test.security.MySecurityMetadataSource.<init>(MySecurityMetadataSource.java:51)
atsun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
atsun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
atsun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
atjava.lang.reflect.Constructor.newInstance(Constructor.java:513)
atorg.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:147)
...63 more
問題出在com.test.security.MySecurityMetadataSource.loadResourceDefine(MySecurityMetadataSource.java:81)上面。
網上給出的大部分解決方法是在xml裡面配置強制注入resourcesServiceImpl，但是這樣做很不靈活，而且由於大部分程式碼都已經用了註解來配置注入，所以不建議使用xml再來配置注入。那麼究竟是什麼原因呢？其實答案很簡單，就是在MySecurityMetadataSource.java中應該把兩個自定義構造器去掉。如同我在下面的註釋所說：
不要使用自定義構造方法，否則會導致注入會出錯？應該是因為構造器中呼叫了loadResourceDefine方法，先於service注入，所以丟擲異常。
我們這裡並不需要自定義構造器，因為在使用註解注入時，注入會自動進行，當你使用了自定義構造器，由於裡面呼叫了loadResourceDefine();而構造器在注入發生前就被呼叫了，所以就會先執行loadResourceDefine();，此時注入還沒進行，因而就會丟擲空指標異常了。
applicationContext-security.xml:
<?xml version="1.0"encoding="UTF-8"?>
<beans:beans xmlns="http://www.springframework.org/schema/security"
xmlns:beans="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/securityhttp://www.springframework.org/schema/security/spring-security-3.0.xsd">
<!--
<global-method-security pre-post-annotations="enabled"/> -->
<global-method-security secured-annotations="enabled" jsr250-annotations="enabled"></global-method-security>
<http access-denied-page="/access_denied.jsp" use-expressions="true" entry-point-ref="authenticationProcessingFilterEntryPoint">
<!-- 該路徑下的資源不用過濾 -->
<intercept-url pattern="/js/**" filters="none"/>
<!-- <logout invalidate-session="true" logout-success-url="/login.jsp"/>-->
<logout invalidate-session="true" logout-url="/j_spring_security_logout"success-handler-ref="customLogoutSuccessHandler" />
<!-- 實現免登陸驗證 -->
<remember-me />
<!--
<form-login login-page="/login.jsp"default-target-url="/frame.jsp"always-use-default-target="true"/>
-->
<session-management invalid-session-url="/login.jsp">
<concurrency-control max-sessions="100" error-if-maximum-exceeded="false"/>
</session-management>
<custom-filter ref="loginFilter" position="FORM_LOGIN_FILTER" />
<custom-filter ref="securityFilter"before="FILTER_SECURITY_INTERCEPTOR"/>
</http>
<!-- 未登入的切入點 -->
<beans:bean id="authenticationProcessingFilterEntryPoint"class="org.springframework.security.web.authentication.LoginUrlAuthenticationEntryPoint">
<beans:property name="loginFormUrl"value="/login.jsp"></beans:property>
</beans:bean>
<!-- 退出登入的切入點 -->
<beans:bean id="customLogoutSuccessHandler" class="com.test.security.CustomLogoutSuccessHandler">
</beans:bean>
<!-- 登入驗證器 -->
<beans:bean id="loginFilter"
class="com.test.security.MyUsernamePasswordAuthenticationFilter">
<!-- 處理登入 -->
<beans:property name="filterProcessesUrl"value="/j_spring_security_check"></beans:property>
<beans:property name="authenticationSuccessHandler"ref="loginLogAuthenticationSuccessHandler"></beans:property>
<beans:property name="authenticationFailureHandler"ref="simpleUrlAuthenticationFailureHandler"></beans:property>
<beans:property name="authenticationManager"ref="myAuthenticationManager"></beans:property>
</beans:bean>
<beans:bean id="loginLogAuthenticationSuccessHandler"
class="org.springframework.security.web.authentication.SavedRequestAwareAuthenticationSuccessHandler">
<beans:property name="defaultTargetUrl"value="/index.jsp"></beans:property>
</beans:bean>
<beans:bean id="simpleUrlAuthenticationFailureHandler"
class="org.springframework.security.web.authentication.SimpleUrlAuthenticationFailureHandler">
<beans:property name="defaultFailureUrl"value="/login.jsp"></beans:property>
</beans:bean>
<!-- 認證過濾器 -->
<beans:bean id="securityFilter"class="com.test.security.MySecurityFilter">
<!-- 使用者擁有的許可權 -->
<beans:property name="authenticationManager" ref="myAuthenticationManager" />
<!-- 使用者是否擁有所請求資源的許可權 -->
<beans:property name="accessDecisionManager" ref="myAccessDecisionManager" />
<!-- 資源與許可權對應關係 -->
<beans:property name="securityMetadataSource" ref="mySecurityMetadataSource" />
</beans:bean>
<!-- 實現了UserDetailsService的Bean -->
<authentication-manager alias="myAuthenticationManager">
<authentication-provider user-service-ref="myUserDetailServiceImpl"/>
</authentication-manager>
</beans:beans>
MySecurityMetadataSource:
package com.test.security;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.Map.Entry;
import javax.annotation.PostConstruct;
import javax.annotation.Resource;
import org.springframework.security.access.ConfigAttribute;
import org.springframework.security.access.SecurityConfig;
import org.springframework.security.web.FilterInvocation;
import org.springframework.security.web.access.intercept.FilterInvocationSecurityMetadataSource;
import org.springframework.stereotype.Component;
import com.test.bean.Resources;
import com.test.dao.IResourcesDao;
import com.test.service.IResourcesService;
//1 載入資源與許可權的對應關係
@Component("mySecurityMetadataSource")
public class MySecurityMetadataSource implements FilterInvocationSecurityMetadataSource {
/*不要使用自定義構造方法，否則導致注入會出錯？應該是構造器中呼叫了loadResourceDefine方法，先於service注入，所以丟擲異常。
public MySecurityMetadataSource() {
loadResourceDefine();
}
//由spring呼叫
public MySecurityMetadataSource(IResourcesService resourcesServiceImpl) {
this.resourcesServiceImpl = resourcesServiceImpl;
loadResourceDefine();
}*/
@Resource
private IResourcesService resourcesServiceImpl;
private static Map<String, Collection<ConfigAttribute>> resourceMap = null;
public Collection<ConfigAttribute> getAllConfigAttributes() {
// TODO Auto-generated method stub
return null;
}
public boolean supports(Class<?> clazz) {
// TODO Auto-generated method stub
return true;
}
//載入所有資源與許可權的關係
@PostConstruct
private void loadResourceDefine() {
if(resourceMap == null) {
resourceMap = new HashMap<String, Collection<ConfigAttribute>>();
List<Resources> resources = this.resourcesServiceImpl.findAll();
//List<Resources> resources = new ArrayList();
for (Resources resource : resources) {
Collection<ConfigAttribute> configAttributes = new ArrayList<ConfigAttribute>();
//以許可權名封裝為Spring的security Object
ConfigAttribute configAttribute = new SecurityConfig(resource.getName());
configAttributes.add(configAttribute);
resourceMap.put(resource.getUrl(), configAttributes);
}
}
Set<Entry<String, Collection<ConfigAttribute>>> resourceSet = resourceMap.entrySet();
Iterator<Entry<String, Collection<ConfigAttribute>>> iterator = resourceSet.iterator();
System.out.println("MySecurityMetadataSource:loadResourceDefine()");
}
//返回所請求資源所需要的許可權
public Collection<ConfigAttribute> getAttributes(Object object) throws IllegalArgumentException {
System.out.println("MySecurityMetadataSource:getAttributes()");
String requestUrl = ((FilterInvocation) object).getRequestUrl();
System.out.println("requestUrl is " + requestUrl);
if(resourceMap == null) {
loadResourceDefine();
}
Collection<ConfigAttribute> c = resourceMap.get(requestUrl);
System.out.println("MySecurityMetadataSource Collection<ConfigAttribute>:"+c);
return c;
}
}