[簡介]
對于一個典型的Web應(yīng)用，完善的認(rèn)證和授權(quán)機(jī)制是必不可少的，在SpringFramework中，Juergen Hoeller提供的范例JPetStore給了一些這方面的介紹，但還遠(yuǎn)遠(yuǎn)不夠，Acegi是一個專門為SpringFramework提供安全機(jī)制的 項(xiàng)目，全稱為Acegi Security System for Spring，當(dāng)前版本為0.5.1，就其目前提供的功能，應(yīng)該可以滿足絕大多數(shù)應(yīng)用的需求。
本文的主要目的是希望能夠說明如何在基于Spring構(gòu)架的Web應(yīng)用中使用Acegi，而不是詳細(xì)介紹其中的每個接口、每個類。注意，即使對已經(jīng)存在的Spring應(yīng)用，通過下面介紹的步驟，也可以馬上享受到Acegi提供的認(rèn)證和授權(quán)。
[基礎(chǔ)工作]
在你的Web應(yīng)用的lib中添加Acegi下載包中的acegi-security.jar
[web.xml]
實(shí)現(xiàn)認(rèn)證和授權(quán)的最常用的方法是通過filter，Acegi亦是如此，通常Acegi需要在web.xml添加以下5個filter:
<filter>
? <filter-name>Acegi Channel Processing Filter</filter-name>
? <filter-class>net.sf.acegisecurity.util.FilterToBeanProxy</filter-class>
? <init-param>
??? <param-name>targetClass</param-name>
??? <param-value>net.sf.acegisecurity.securechannel.ChannelProcessingFilter</param-value>
? </init-param>
</filter>
<filter>
? <filter-name>Acegi Authentication Processing Filter</filter-name>
? <filter-class>net.sf.acegisecurity.util.FilterToBeanProxy</filter-class>
? <init-param>
??? <param-name>targetClass</param-name>
??? <param-value>net.sf.acegisecurity.ui.webapp.AuthenticationProcessingFilter</param-value>
? </init-param>
</filter>
<filter>
? <filter-name>Acegi HTTP BASIC Authorization Filter</filter-name>
? <filter-class>net.sf.acegisecurity.util.FilterToBeanProxy</filter-class>
? <init-param>
??? <param-name>targetClass</param-name>
??? <param-value>net.sf.acegisecurity.ui.basicauth.BasicProcessingFilter</param-value>
? </init-param>
</filter>
<filter>
? <filter-name>Acegi Security System for Spring Auto Integration Filter</filter-name>
? <filter-class>net.sf.acegisecurity.ui.AutoIntegrationFilter</filter-class>
</filter>
<filter>
? <filter-name>Acegi HTTP Request Security Filter</filter-name>
? <filter-class>net.sf.acegisecurity.util.FilterToBeanProxy</filter-class>
? <init-param>
??? <param-name>targetClass</param-name>
??? <param-value>net.sf.acegisecurity.intercept.web.SecurityEnforcementFilter</param-value>
? </init-param>
</filter>
最先引起迷惑的是net.sf.acegisecurity.util.FilterToBeanProxy，Acegi自己的文檔上解釋是： “What? FilterToBeanProxy does is delegate the Filter's methods through to a bean which is obtained from the
Spring application context. This enables the bean to benefit from the Spring application context lifecycle support and configuration flexibility.”，如希望深究的話，去看看源代碼應(yīng)該不難理解。
再下來就是添加filter-mapping了：
<filter-mapping>
? <filter-name>Acegi Channel Processing Filter</filter-name>
? <url-pattern>/*</url-pattern>
</filter-mapping>
<filter-mapping>
? <filter-name>Acegi Authentication Processing Filter</filter-name>
? <url-pattern>/*</url-pattern>
</filter-mapping>
<filter-mapping>
? <filter-name>Acegi HTTP BASIC Authorization Filter</filter-name>
? <url-pattern>/*</url-pattern>
</filter-mapping>
<filter-mapping>
? <filter-name>Acegi Security System for Spring Auto Integration Filter</filter-name>
? <url-pattern>/*</url-pattern>
</filter-mapping>
<filter-mapping>
? <filter-name>Acegi HTTP Request Security Filter</filter-name>
? <url-pattern>/*</url-pattern>
</filter-mapping>
這里，需要注意以下兩點(diǎn)：
1) 這幾個filter的順序是不能更改的，順序不對將無法正常工作；
2) 如果你的應(yīng)用不需要安全傳輸，如https，則將"Acegi Channel Processing Filter"相關(guān)內(nèi)容注釋掉即可；
3) 如果你的應(yīng)用不需要Spring提供的遠(yuǎn)程訪問機(jī)制，如Hessian and Burlap，將"Acegi HTTP BASIC Authorization
Filter"相關(guān)內(nèi)容注釋掉即可。
[applicationContext.xml]
接下來就是要添加applicationContext.xml中的內(nèi)容了，從剛才FilterToBeanFactory的解釋可以看出，真正的filter都
在Spring的applicationContext中管理：
1) 首先，你的數(shù)據(jù)庫中必須具有保存用戶名和密碼的table，Acegi要求table的schema必須如下：
CREATE TABLE users (
?? ?username VARCHAR(50) NOT NULL PRIMARY KEY,
?? ?password VARCHAR(50) NOT NULL,
?? ?enabled BIT NOT NULL
);
CREATE TABLE authorities (
?? ?username VARCHAR(50) NOT NULL,
?? ?authority VARCHAR(50) NOT NULL
);
CREATE UNIQUE INDEX ix_auth_username ON authorities ( username, authority );
ALTER TABLE authorities ADD CONSTRAINT fk_authorities_users foreign key (username) REFERENCES users
(username);
2) 添加訪問你的數(shù)據(jù)庫的datasource和Acegi的jdbcDao，如下：
<bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
? <property name="driverClassName"><value>${jdbc.driverClassName}</value></property>
? <property name="url"><value>${jdbc.url}</value></property>
? <property name="username"><value>${jdbc.username}</value></property>
? <property name="password"><value>${jdbc.password}</value></property>
</bean>
<bean id="jdbcDaoImpl" class="net.sf.acegisecurity.providers.dao.jdbc.JdbcDaoImpl">
? <property name="dataSource"><ref bean="dataSource"/></property>
</bean>
3) 添加DaoAuthenticationProvider:
<bean id="daoAuthenticationProvider" class="net.sf.acegisecurity.providers.dao.DaoAuthenticationProvider">
? <property name="authenticationDao"><ref bean="authenticationDao"/></property>
? <property name="userCache"><ref bean="userCache"/></property>
</bean>
<bean id="userCache" class="net.sf.acegisecurity.providers.dao.cache.EhCacheBasedUserCache">
? <property name="minutesToIdle"><value>5</value></property>
</bean>
如果你需要對密碼加密，則在daoAuthenticationProvider中加入：<property name="passwordEncoder"><ref
bean="passwordEncoder"/></property>，Acegi提供了幾種加密方法，詳細(xì)情況可看包
net.sf.acegisecurity.providers.encoding
4) 添加authenticationManager:
<bean id="authenticationManager" class="net.sf.acegisecurity.providers.ProviderManager">
? <property name="providers">
??? <list>
????? <ref bean="daoAuthenticationProvider"/>
??? </list>
?? </property>
</bean>
5) 添加accessDecisionManager:
<bean id="accessDecisionManager" class="net.sf.acegisecurity.vote.AffirmativeBased">
? <property name="allowIfAllAbstainDecisions">
??? <value>false</value>
? </property>
? <property name="decisionVoters">
??? <list><ref bean="roleVoter"/></list>
? </property>
</bean>
<bean id="roleVoter" class="net.sf.acegisecurity.vote.RoleVoter"/>
6) 添加authenticationProcessingFilterEntryPoint:
<bean id="authenticationProcessingFilterEntryPoint"
class="net.sf.acegisecurity.ui.webapp.AuthenticationProcessingFilterEntryPoint">
? <property name="loginFormUrl"><value>/acegilogin.jsp</value></property>
? <property name="forceHttps"><value>false</value></property>
</bean>
其中acegilogin.jsp是登陸頁面，一個最簡單的登錄頁面如下：
<%@ taglib prefix='c' uri='http://java.sun.com/jstl/core' %>
<%@ page import="net.sf.acegisecurity.ui.AbstractProcessingFilter" %>
<%@ page import="net.sf.acegisecurity.AuthenticationException" %>
<html>
? <head>
??? <title>Login</title>
? </head>
? <body>
??? <h1>Login</h1>
??? <form action="<c:url value='j_acegi_security_check'/>" method="POST">
????? <table>
??????? <tr><td>User:</td><td><input type='text' name='j_username'></td></tr>
??????? <tr><td>Password:</td><td><input type='password' name='j_password'></td></tr>
??????? <tr><td colspan='2'><input name="submit" type="submit"></td></tr>
??????? <tr><td colspan='2'><input name="reset" type="reset"></td></tr>
????? </table>
??? </form>
? </body>
</html>
7) 添加filterInvocationInterceptor:
<bean id="filterInvocationInterceptor"
class="net.sf.acegisecurity.intercept.web.FilterSecurityInterceptor">
? <property name="authenticationManager">
??? <ref bean="authenticationManager"/>
? </property>
? <property name="accessDecisionManager">
??? <ref bean="accessDecisionManager"/>
? </property>
? <property name="objectDefinitionSource">
??? <value>
????? CONVERT_URL_TO_LOWERCASE_BEFORE_COMPARISON
????? \A/sec/administrator.*\Z=ROLE_SUPERVISOR
????? \A/sec/user.*\Z=ROLE_TELLER
??? </value>
? </property>
</bean>
這里請注意，要objectDefinitionSource中定義哪些頁面需要權(quán)限訪問，需要根據(jù)自己的應(yīng)用需求進(jìn)行修改，我上面給出
的定義的意思是這樣的：
?a. CONVERT_URL_TO_LOWERCASE_BEFORE_COMPARISON意思是在比較請求路徑時全部轉(zhuǎn)換為小寫
?b. \A/sec/administrator.*\Z=ROLE_SUPERVISOR意思是只有權(quán)限為ROLE_SUPERVISOR才能訪問/sec/administrator*的頁面
?c. \A/sec/user.*\Z=ROLE_TELLER意思是只有權(quán)限為ROLE_TELLER的用戶才能訪問/sec/user*的頁面
8) 添加securityEnforcementFilter:
<bean id="securityEnforcementFilter" class="net.sf.acegisecurity.intercept.web.SecurityEnforcementFilter">
? <property name="filterSecurityInterceptor">
??? <ref bean="filterInvocationInterceptor"/>
? </property>
? <property name="authenticationEntryPoint">
??? <ref bean="authenticationProcessingFilterEntryPoint"/>
? </property>
</bean>
9) 添加authenticationProcessingFilter:
<bean id="authenticationProcessingFilter"
class="net.sf.acegisecurity.ui.webapp.AuthenticationProcessingFilter">
? <property name="authenticationManager">
??? <ref bean="authenticationManager"/>
? </property>
? <property name="authenticationFailureUrl">
??? <value>/loginerror.jsp</value>
? </property>
? <property name="defaultTargetUrl">
??? <value>/</value>
? </property>
? <property name="filterProcessesUrl">
??? <value>/j_acegi_security_check</value>
? </property>
</bean>
其中authenticationFailureUrl是認(rèn)證失敗的頁面。
10) 如果需要一些頁面通過安全通道的話，添加下面的配置:
<bean id="channelProcessingFilter" class="net.sf.acegisecurity.securechannel.ChannelProcessingFilter">
? <property name="channelDecisionManager">
??? <ref bean="channelDecisionManager"/>
? </property>
? <property name="filterInvocationDefinitionSource">
??? <value>
????? CONVERT_URL_TO_LOWERCASE_BEFORE_COMPARISON
????? \A/sec/administrator.*\Z=REQUIRES_SECURE_CHANNEL
????? \A/acegilogin.jsp.*\Z=REQUIRES_SECURE_CHANNEL
????? \A/j_acegi_security_check.*\Z=REQUIRES_SECURE_CHANNEL
????? \A.*\Z=REQUIRES_INSECURE_CHANNEL
??? </value>
? </property>
</bean>
<bean id="channelDecisionManager" class="net.sf.acegisecurity.securechannel.ChannelDecisionManagerImpl">
? <property name="channelProcessors">
??? <list>
????? <ref bean="secureChannelProcessor"/>
????? <ref bean="insecureChannelProcessor"/>
??? </list>
? </property>
</bean>
<bean id="secureChannelProcessor" class="net.sf.acegisecurity.securechannel.SecureChannelProcessor"/>
<bean id="insecureChannelProcessor" class="net.sf.acegisecurity.securechannel.InsecureChannelProcessor"/>
[缺少了什么？]
Acegi目前提供了兩種"secure object"，分別對頁面和方法進(jìn)行安全認(rèn)證管理，我這里介紹的只是利用
FilterSecurityInterceptor對訪問頁面的權(quán)限控制，除此之外，Acegi還提供了另外一個Interceptor——
MethodSecurityInterceptor，它結(jié)合runAsManager可實(shí)現(xiàn)對對象中的方法的權(quán)限控制，使用方法可參看Acegi自帶的文檔
和contact范例。
[最后要說的]
本來以為只是說明如何使用Acegi而已，應(yīng)該非常簡單，但真正寫起來才發(fā)現(xiàn)想要條理清楚的理順?biāo)行枰腷ean還是很
困難的，但愿我沒有遺漏太多東西，如果我的文章有什么遺漏或錯誤的話，還請參看Acegi自帶的quick-start范例，但請
注意，這個范例是不能直接拿來用的。