Feiing <视觉错误>

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 :
[code:1]
<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>

[/code:1]
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:

[code:1]
/*
* 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);
}


}

[/code:1]

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 :

[code:1]
/*
* 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();


}
[/code:1]

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
[code:1]
/*
* 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;
}

}
[/code:1]

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 :

[code:1]
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());
}
}
[/code:1]

配置:


It’s Over Now.

本文引用代码及配置文件参见附件.[/url]