本文原出处 : http://starcraft.blogdriver.com/starcraft/1089862.html

Acegi 资源配置动态扩展实现

王 政 (Feiing) 于 2005-12-11

1. 问题提出

在使用 Acegi Security Framework 的过程中, 如果细心的话, 会发现其资源和角色配置是在配置文件中的, 下面是 Appfuse 中相关配置 :

    <bean id="filterInvocationInterceptor" class="net.sf.acegisecurity.intercept.web.FilterSecurityInterceptor">
        <property name="authenticationManager"><ref local="authenticationManager"/></property>
        <property name="accessDecisionManager"><ref local="accessDecisionManager"/></property>
         <property name="objectDefinitionSource">
            <value>
                CONVERT_URL_TO_LOWERCASE_BEFORE_COMPARISON
                PATTERN_TYPE_APACHE_ANT
                /signup.html=ROLE_ANONYMOUS,admin,tomcat
  
                /clickstreams.jsp=admin
            </value>
        </property>
    </bean>

上面的配置从功能上实现了资源与角色的映射, 但用户可能会提出在运行期动态改变权限分配的需求, 配置文件策略可能略显不足, 下面我将提供一种基于数据库的策略解决此问题.

2. E-R 模型

下图是需要的 E-R 模型


图1 Acegi 标准 RBAC E-R设计

图中的用户与角色不再多做解释, 我们主要关注一下 Permission 表 和 Resource 表, 这里 Resource 表用于存储系统资源, 在 web 层一般来说就是 url, 如果使用 acl, 就是 aclClass, 此时 Permission 表中的 aclMask 用来存储对应的 acl 权限, 考虑到 acl 在 web 项目中使用率不高, 下面我将着重介绍 web 层的权限控制, 对 acl 有兴趣的读者可以自己参阅 Acegi Reference Guide.


3. 如何阻止 acegi 从配置文件读取权限配置



从 Appfuse 中的示例性配置可以看出, acegi 对权限配置的要求是 “ 资源 = 角色1, 角色2 …  角色 n ”, 看过源代码的读者应该知道,  最终这些配置将被组装为 net.sf.acegisecurity.intercept. ObjectDefinitionSource(web 层对应的实现是 net.sf.acegisecurity.intercept.web. FilterInvocationDefinitionSource), 那么我们怎么才能用数据库的数据来组装 FilterInvocationDefinitionSource ? 这里涉及到一个 PropertyEditor 问题, 在 Acegi 中, FilterInvocationDefinitionSource 是通过 net.sf.acegisecurity.intercept.web.FilterInvocationDefinitionSourceEditor 组装的, 假如我们不想让 FilterInvocationDefinitionSourceEditor 从配置文件中读取权限配置, 就需要自己实现一个 ProdertyEditor 来覆盖默认实现, 下面是我的 配置 :


图2 customerEditorConfigurer 配置

那么, 这个 PropertyEditor 中需要做些什么呢 ? 要做的就是使用一个比较特殊的标记, 当遇到这个特殊标记的时候直接略过解析,  我这里使用的标记是 “DONT_USE_ME”, 然后在 PropertyEditor 中简单的如下实现即可:

/*
 * Copyright 2004-2005 wangz.
 * Project shufe_newsroom
 */
package com.skyon.um.security.acegi.intercept.web;

import java.beans.PropertyEditorSupport;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.StringReader;

import net.sf.acegisecurity.ConfigAttributeDefinition;
import net.sf.acegisecurity.ConfigAttributeEditor;
import net.sf.acegisecurity.intercept.web.FilterInvocationDefinitionMap;
import net.sf.acegisecurity.intercept.web.PathBasedFilterInvocationDefinitionMap;
import net.sf.acegisecurity.intercept.web.RegExpBasedFilterInvocationDefinitionMap;

import org.apache.commons.lang.StringUtils;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
 * @since 2005-8-4
 * @author 王政
 * @version $Id: FilterInvocationDefinitionSourceDynamicExtentionEditor.java,v 1.2 2005/11/04 15:55:07 wangzheng Exp $
 */
public class FilterInvocationDefinitionSourceDynamicExtentionEditor extends
        PropertyEditorSupport {

    public static final String ANT_PATH_KEY = "PATTERN_TYPE_APACHE_ANT";
    
    public static final String LOWER_CASE_URL_KEY = "CONVERT_URL_TO_LOWERCASE_BEFORE_COMPARISON";

    public static final String DONT_USE_ME_KEY = "DONT_USE_ME";
    
    public static final String STAND_DELIM_CHARACTER = ",";

    private static final Log logger = LogFactory.getLog(FilterInvocationDefinitionSourceDynamicExtentionEditor.class);
    
    /**
     * @see java.beans.PropertyEditorSupport#setAsText(java.lang.String)
     */
    public void setAsText(String text) throws IllegalArgumentException {                
        FilterInvocationDefinitionMap source = new RegExpBasedFilterInvocationDefinitionMap();
               
        if (StringUtils.isBlank(text)) {
            // Leave target object empty
        } else {         
            // Check if we need to override the default definition map
            if (text.lastIndexOf(ANT_PATH_KEY) != -1) {
                source = new PathBasedFilterInvocationDefinitionMap();

                if (logger.isDebugEnabled()) {
                    logger.debug(("Detected PATTERN_TYPE_APACHE_ANT directive; using Apache Ant style path expressions"));
                }
            }

            if (text.lastIndexOf(LOWER_CASE_URL_KEY) != -1) {
                if (logger.isDebugEnabled()) {
                    logger.debug("Instructing mapper to convert URLs to lowercase before comparison");
                }

                source.setConvertUrlToLowercaseBeforeComparison(true);
            }
            
            if (text.indexOf(DONT_USE_ME_KEY) != -1) {
                if (logger.isDebugEnabled()) {
                    logger.debug("DETECTED " + DONT_USE_ME_KEY + " directive;  skip parse, Use " + EhCacheBasedFilterInvocationDefinitionSourceCache.class + " to parse!");
                }
                addSecureUrl(source, "/dontuseme", "dontuseme");
            } else {
                BufferedReader br = new BufferedReader(new StringReader(text));
                int counter = 0;
                String line;

                while (true) {
                    counter++;

                    try {
                        line = br.readLine();
                    } catch (IOException ioe) {
                        throw new IllegalArgumentException(ioe.getMessage());
                    }

                    if (line == null) {
                        break;
                    }

                    line = line.trim();

                    if (logger.isDebugEnabled()) {
                        logger.debug("Line " + counter + ": " + line);
                    }

                    if (line.startsWith("//")) {
                        continue;
                    }

                    if (line.equals(LOWER_CASE_URL_KEY)) {
                        continue;
                    }

                    if (line.lastIndexOf('=') == -1) {
                        continue;
                    }

                    // Tokenize the line into its name/value tokens
                    String[] nameValue = org.springframework.util.StringUtils.delimitedListToStringArray(line, "=");
                    String name = nameValue[0];
                    String value = nameValue[1];

                    addSecureUrl(source, name, value);                
                }
            }
            


        }

        setValue(source);
    }
    

    /**
     * @param source
     * @param name
     * @param value
     * @throws IllegalArgumentException
     */
    private void addSecureUrl(FilterInvocationDefinitionMap source, String name, String value) 
        throws IllegalArgumentException {
        
        // Convert value to series of security configuration attributes
        ConfigAttributeEditor configAttribEd = new ConfigAttributeEditor();
        configAttribEd.setAsText(value);

        ConfigAttributeDefinition attr = (ConfigAttributeDefinition) configAttribEd.getValue();

        // Register the regular expression and its attribute
        source.addSecureUrl(name, attr);
    }


}

Ok, 现在 FilterInvocationDefinitionSourceDynamicExtentionEditor 遇到配置文件中的 “DONT_USE_ME” 时将直接略过, 下面是我的 filterInvocationInterceptor 配置:

图3 filterInvocationInterceptor 配置

现在, 我们已经成功阻止 acegi 从配置文件读取权限配置, 下一个问题就是:


4. 如何从表中数据组装 FilterInvocationDefinitionSource



为了实现此功能, 需要一个自定义的资源定义接口来提供 FilterInvocationDefinitionSource,  此接口可能会是这样 :

/*
 * Copyright 2005-2010 the original author or autors
 *  
 *    http://www.skyon.com.cn
 *
 * Project { SkyonFramwork }
 */
package com.skyon.um.security.acegi.intercept.web;

import net.sf.acegisecurity.intercept.web.FilterInvocationDefinitionSource;

import org.springframework.beans.factory.FactoryBean;

import com.skyon.framework.spring.ehcache.FlushableCache;

/**
 * <class>FilterInvocationDefinitionSourceCache</class> use to hold the global FilterInvocationDefinitionSource,
 * it keeps a static variable , if the source been changed(generally the database data),  the reload method should be called
 * 
 * @see com.skyon.um.security.acegi.intercept.event.FilterInvocationDefinitionSourceChangedEvent
 * @see com.skyon.um.security.acegi.intercept.event.FilterInvocationDefinitionSourceListener
 * @see com.skyon.um.security.acegi.intercept.web.SecurityEnforcementDynamicExtensionFilter
 * @since 2005-8-7
 * @author 王政
 * @version $Id: FilterInvocationDefinitionSourceCache.java,v 1.1 2005/11/04 15:55:07 wangzheng Exp $
 */
public interface FilterInvocationDefinitionSourceCache extends FactoryBean, FlushableCache {
	
	/** The Perl5 expression  */
    int REOURCE_EXPRESSION_PERL5_REG_EXP = 1;
    
    /** The ant path expression */
    int RESOURCE_EXPRESSION_ANT_PATH_KEY = 2;
    
    /**
     * Set resource expression, the value must be {@link #REOURCE_EXPRESSION_PERL5_REG_EXP} or {@link #RESOURCE_EXPRESSION_ANT_PATH_KEY}
     * @see #REOURCE_EXPRESSION_PERL5_REG_EXP
     * @see #RESOURCE_EXPRESSION_ANT_PATH_KEY
     * @param resourceExpression the resource expression
     */
    void setResourceExpression(int resourceExpression);
    
    /**
     * Set whether convert url to lowercase before comparison
     * @param convertUrlToLowercaseBeforeComparison whether convertUrlToLowercaseBeforeComparison
     */
    void setConvertUrlToLowercaseBeforeComparison(boolean convertUrlToLowercaseBeforeComparison);
    
	/**
	 * Get the defination source, generally from a database schema
	 * @return the defination source
	 */
    FilterInvocationDefinitionSource getFilterInvocationDefinitionSource();
           
 
}

其核心方法是  FilterInvocationDefinitionSource getFilterInvocationDefinitionSource(), 此方法将代替配置文件提供资源和角色的配置, 下面是实现

/*
 * Copyright 2005-2010 the original author or autors
 *  
 *    http://www.skyon.com.cn
 *
 * Project { SkyonFramwork }
 */
package com.skyon.um.security.acegi.intercept.web;

import net.sf.acegisecurity.ConfigAttributeDefinition;
import net.sf.acegisecurity.ConfigAttributeEditor;
import net.sf.acegisecurity.intercept.web.FilterInvocationDefinitionMap;
import net.sf.acegisecurity.intercept.web.FilterInvocationDefinitionSource;
import net.sf.acegisecurity.intercept.web.PathBasedFilterInvocationDefinitionMap;
import net.sf.acegisecurity.intercept.web.RegExpBasedFilterInvocationDefinitionMap;
import net.sf.ehcache.Cache;
import net.sf.ehcache.Element;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.util.Assert;

import com.skyon.framework.spring.ehcache.CacheUtils;
import com.skyon.framework.spring.ehcache.SerializableObjectProvider;
import com.skyon.framework.spring.support.MandatorySingletonBeanSupport;

/**
 * @since 2005-8-7
 * @author 王政
 * @version $Id: EhCacheBasedFilterInvocationDefinitionSourceCache.java,v 1.2 2005/11/17 09:38:25 wangzheng Exp $
 */
public class EhCacheBasedFilterInvocationDefinitionSourceCache extends MandatorySingletonBeanSupport 
	implements FilterInvocationDefinitionSourceCache, InitializingBean {
    
    private static final Log logger = LogFactory.getLog(EhCacheBasedFilterInvocationDefinitionSourceCache.class);
    
    private int resourceExpression;
    
    private boolean convertUrlToLowercaseBeforeComparison = false;
        
    private ResourceMappingProvider resourceMappingProvider;
    
    private Cache cache;
    
    private Object lock = new Object();
    
    /**
     * @see com.skyon.um.security.acegi.intercept.web.FilterInvocationDefinitionSourceCache#getFilterInvocationDefinitionSource()
     */
    public FilterInvocationDefinitionSource getFilterInvocationDefinitionSource() {
    	synchronized (lock) {
        	Element element = CacheUtils.get(getCache(), "key");
        	
        	if (element == null) {
        		FilterInvocationDefinitionSource definitionSource = (FilterInvocationDefinitionSource) getFilterInvocationDefinitionSourceFromBackend();
        		element = new Element("key", new SerializableObjectProvider(definitionSource));
        		getCache().put(element);
        	}
        	
        	return (FilterInvocationDefinitionSource) ((SerializableObjectProvider) element.getValue()).getSourceObject();
    	}
    }
            
	public void flushCache() {
		CacheUtils.flushCache(getCache());
		getFilterInvocationDefinitionSource();
	}
    
    private FilterInvocationDefinitionMap getFilterInvocationDefinitionSourceFromBackend() {        
    	logger.info(" 开始加载系统资源权限数据到缓存... ");
    	
    	FilterInvocationDefinitionMap definitionSource = null;
        
    	switch (resourceExpression) {
            case REOURCE_EXPRESSION_PERL5_REG_EXP : {
                definitionSource = new RegExpBasedFilterInvocationDefinitionMap();
                break;
            }
            case RESOURCE_EXPRESSION_ANT_PATH_KEY : {
                definitionSource = new PathBasedFilterInvocationDefinitionMap();
                break;
            }
            default : {
                throwException();
            }
        }
        
        definitionSource.setConvertUrlToLowercaseBeforeComparison(isConvertUrlToLowercaseBeforeComparison());
        
        ResourceMapping[] mappings = getResourceMappingProvider().getResourceMappings();
        if (mappings == null || mappings.length ==0) {
            return definitionSource;
        }
        
        for (int i = 0; i < mappings.length; i++) {
            ResourceMapping mapping = mappings[i];
            String[] recipents = mapping.getRecipients();
            
            if (recipents == null || recipents.length == 0) {
                if (logger.isErrorEnabled()) {
                    logger.error("Notice, the resource : " + mapping.getResourcePath() + " has no recipents, it will access by any one ! ");
                }
                continue;
            }
            
            StringBuffer valueBuffer = new StringBuffer();
            for (int j = 0; j < recipents.length; j++) {
                valueBuffer.append(recipents[j]);
                if (j < recipents.length - 1) {
                    valueBuffer.append(FilterInvocationDefinitionSourceDynamicExtentionEditor.STAND_DELIM_CHARACTER);
                }
            }
            String value = valueBuffer.toString();                    
            addSecureUrl(definitionSource, mapping.getResourcePath(), value);
         }
        
        logger.info(" 成功加载系统资源权限数据到缓存 ! ");
        return definitionSource;
    }

    /**
     * @param source
     * @param name
     * @param value
     * @throws IllegalArgumentException
     */
    private synchronized void addSecureUrl(FilterInvocationDefinitionMap source, String name, String value) 
        throws IllegalArgumentException {
        
        // Convert value to series of security configuration attributes
        ConfigAttributeEditor configAttribEd = new ConfigAttributeEditor();
        configAttribEd.setAsText(value);

        ConfigAttributeDefinition attr = (ConfigAttributeDefinition) configAttribEd.getValue();

        // Register the regular expression and its attribute
        source.addSecureUrl(name, attr);
    }
    

    public void afterPropertiesSet() throws Exception {
        if (resourceExpression != REOURCE_EXPRESSION_PERL5_REG_EXP && resourceExpression != RESOURCE_EXPRESSION_ANT_PATH_KEY) {
            throwException();
        }        
        Assert.notNull(getResourceMappingProvider(), " resourceMappingProvider must be specified");      
        Assert.notNull(getCache(), " cache must be specified");    
    }


    /**
     * @throws IllegalArgumentException
     */
    private void throwException() throws IllegalArgumentException {
        throw new IllegalArgumentException("wrong resourceExpression value");
    }
       
    /**
     * @return Returns the resourceMappingProvider.
     */
    public ResourceMappingProvider getResourceMappingProvider() {
        return resourceMappingProvider;
    }

    /**
     * @param resourceMappingProvider The resourceMappingProvider to set.
     */
    public void setResourceMappingProvider(ResourceMappingProvider resourceMappingProvider) {
        this.resourceMappingProvider = resourceMappingProvider;
    }

    /**
     * @return Returns the convertUrlToLowercaseBeforeComparison.
     */
    public boolean isConvertUrlToLowercaseBeforeComparison() {
        return convertUrlToLowercaseBeforeComparison;
    }

    /**
     * @param convertUrlToLowercaseBeforeComparison The convertUrlToLowercaseBeforeComparison to set.
     */
    public void setConvertUrlToLowercaseBeforeComparison(
            boolean convertUrlToLowercaseBeforeComparison) {
        this.convertUrlToLowercaseBeforeComparison = convertUrlToLowercaseBeforeComparison;
    }

    /**
     * @return Returns the resourceExpression.
     */
    public int getResourceExpression() {
        return resourceExpression;
    }

    /**
     * @param resourceExpression The resourceExpression to set.
     */
    public void setResourceExpression(int resourceExpression) {
        this.resourceExpression = resourceExpression;
    }


	/**
	 * @return Returns the cache.
	 */
	public Cache getCache() {
		return cache;
	}


	/**
	 * @param cache The cache to set.
	 */
	public void setCache(Cache cache) {
		this.cache = cache;
	}

}

实现采用 EhCache 缓存资源权限配置, 这样如果资源权限数据发生变化, 可以 flush Cache 从数据库重新读取. 至于代码中的 ResourceMapingProvider 实现, 简单的把 Resource 表和 Role 表中的数据读取过来即可, 这里不再赘述.



5. 如何将数据库中的权限配置传递给 FilterInvocationInterceptor


完成以上步骤后, 最后一步就是如何把 FilterInvocationDefinitionSourceCache 中的 FilterInvocationDefinitionSource 传递给 FilterInvocationInterceptor,  Simple implemention :

public class SecurityEnforcementDynamicExtensionFilter extends
        SecurityEnforcementFilter implements InitializingBean {
… 略去 

 public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {    	   	
		// get the defination source form soure holder
		getFilterSecurityInterceptor().setObjectDefinitionSource(getDefinitionSourceCache().getFilterInvocationDefinitionSource());
}
}

配置:


It’s Over Now.

本文引用代码及配置文件参见附件.[/url]