浅谈Spring Security

Spring Security 3.x 出来一段时间了，跟Acegi是大不同了，与2.x的版本也有一些小小的区别，网上有一些文档，也有人翻译Spring Security 3.x的guide，但通过阅读guide，无法马上就能很容易的实现一个完整的实例。

我花了点儿时间，根据以前的实战经验，整理了一份完整的入门教程，供需要的朋友们参考。
1，建一个web project，并导入所有需要的lib，这步就不多讲了。
2，配置web.xml，使用Spring的机制装载：

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee 
    http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>classpath:applicationContext*.xml</param-value>
    </context-param>

    <listener>
        <listener-class>
            org.springframework.web.context.ContextLoaderListener
        </listener-class>
    </listener>

    <filter>
        <filter-name>springSecurityFilterChain</filter-name>
        <filter-class>
            org.springframework.web.filter.DelegatingFilterProxy
        </filter-class>
    </filter>
    <filter-mapping>
        <filter-name>springSecurityFilterChain</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>


    <welcome-file-list>
        <welcome-file>login.jsp</welcome-file>
    </welcome-file-list>
</web-app>

这个文件中的内容我相信大家都很熟悉了，不再多说了。



3.来看看applicationContext-security.xml这个配置文件，关于Spring Security的配置均在其中：

<?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/beans
           http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
           http://www.springframework.org/schema/security
           http://www.springframework.org/schema/security/spring-security-3.0.xsd">

    <http access-denied-page="/403.jsp"><!-- 当访问被拒绝时，会转到403.jsp -->
        <intercept-url pattern="/login.jsp" filters="none" />
        <form-login login-page="/login.jsp"
            authentication-failure-url="/login.jsp?error=true"
            default-target-url="/index.jsp" />
        <logout logout-success-url="/login.jsp" />
        <http-basic />
        <!-- 增加一个filter，这点与Acegi是不一样的，不能修改默认的filter了，这个filter位于FILTER_SECURITY_INTERCEPTOR之前 -->
        <custom-filter before="FILTER_SECURITY_INTERCEPTOR"
            ref="myFilter" />
    </http>

    <!-- 一个自定义的filter，必须包含authenticationManager,accessDecisionManager,securityMetadataSource三个属性，我们的所有控制将在这三个类中实现，解释详见具体配置 -->
    <beans:bean id="myFilter" class="com.robin.erp.fwk.security.MyFilterSecurityInterceptor">
        <beans:property name="authenticationManager"
            ref="authenticationManager" />
        <beans:property name="accessDecisionManager"
            ref="myAccessDecisionManagerBean" />
        <beans:property name="securityMetadataSource"
            ref="securityMetadataSource" />
    </beans:bean>
    
    <!-- 认证管理器，实现用户认证的入口，主要实现UserDetailsService接口即可 -->
    <authentication-manager alias="authenticationManager">
        <authentication-provider
            user-service-ref="myUserDetailService">
            <!--   如果用户的密码采用加密的话，可以加点“盐”
                <password-encoder hash="md5" />
            -->
        </authentication-provider>
    </authentication-manager>
    <beans:bean id="myUserDetailService"
        class="com.robin.erp.fwk.security.MyUserDetailService" />

    <!-- 访问决策器，决定某个用户具有的角色，是否有足够的权限去访问某个资源 -->
    <beans:bean id="myAccessDecisionManagerBean"
        class="com.robin.erp.fwk.security.MyAccessDecisionManager">
    </beans:bean>
    
    <!-- 资源源数据定义，即定义某一资源可以被哪些角色访问 -->
    <beans:bean id="securityMetadataSource"
        class="com.robin.erp.fwk.security.MyInvocationSecurityMetadataSource" />

</beans:beans>

4.来看看自定义filter的实现：

package com.robin.erp.fwk.security;
import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

import org.springframework.security.access.SecurityMetadataSource;
import org.springframework.security.access.intercept.AbstractSecurityInterceptor;
import org.springframework.security.access.intercept.InterceptorStatusToken;
import org.springframework.security.web.FilterInvocation;
import org.springframework.security.web.access.intercept.FilterInvocationSecurityMetadataSource;

public class MyFilterSecurityInterceptor extends AbstractSecurityInterceptor
        implements Filter {

    private FilterInvocationSecurityMetadataSource securityMetadataSource;

    // ~ Methods
    // ========================================================================================================

    /**
     * Method that is actually called by the filter chain. Simply delegates to
     * the {@link #invoke(FilterInvocation)} method.
     * 
     * @param request
     *            the servlet request
     * @param response
     *            the servlet response
     * @param chain
     *            the filter chain
     * 
     * @throws IOException
     *             if the filter chain fails
     * @throws ServletException
     *             if the filter chain fails
     */
    public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain chain) throws IOException, ServletException {
        FilterInvocation fi = new FilterInvocation(request, response, chain);
        invoke(fi);
    }

    public FilterInvocationSecurityMetadataSource getSecurityMetadataSource() {
        return this.securityMetadataSource;
    }

    public Class<? extends Object> getSecureObjectClass() {
        return FilterInvocation.class;
    }

    public void invoke(FilterInvocation fi) throws IOException,
            ServletException {
        InterceptorStatusToken token = super.beforeInvocation(fi);
        try {
            fi.getChain().doFilter(fi.getRequest(), fi.getResponse());
        } finally {
            super.afterInvocation(token, null);
        }
    }

    public SecurityMetadataSource obtainSecurityMetadataSource() {
        return this.securityMetadataSource;
    }

    public void setSecurityMetadataSource(
            FilterInvocationSecurityMetadataSource newSource) {
        this.securityMetadataSource = newSource;
    }

    @Override
    public void destroy() {
    }

    @Override
    public void init(FilterConfig arg0) throws ServletException {
    }

}

最核心的代码就是invoke方法中的InterceptorStatusToken token = super.beforeInvocation(fi);这一句，即在执行doFilter之前，进行权限的检查，而具体的实现已经交给accessDecisionManager了，下文中会讲述。



5.来看看authentication-provider的实现：

package com.robin.erp.fwk.security;
import java.util.ArrayList;
import java.util.Collection;

import org.springframework.dao.DataAccessException;
import org.springframework.security.core.GrantedAuthority;
import org.springframework.security.core.authority.GrantedAuthorityImpl;
import org.springframework.security.core.userdetails.User;
import org.springframework.security.core.userdetails.UserDetails;
import org.springframework.security.core.userdetails.UserDetailsService;
import org.springframework.security.core.userdetails.UsernameNotFoundException;

public class MyUserDetailService implements UserDetailsService {

    @Override
    public UserDetails loadUserByUsername(String username)
            throws UsernameNotFoundException, DataAccessException {
        Collection<GrantedAuthority> auths=new ArrayList<GrantedAuthority>();
        GrantedAuthorityImpl auth2=new GrantedAuthorityImpl("ROLE_ADMIN");
        auths.add(auth2);
        if(username.equals("robin1")){
            auths=new ArrayList<GrantedAuthority>();
            GrantedAuthorityImpl auth1=new GrantedAuthorityImpl("ROLE_ROBIN");
            auths.add(auth1);
        }
        
//        User(String username, String password, boolean enabled, boolean accountNonExpired,
//                    boolean credentialsNonExpired, boolean accountNonLocked, Collection<GrantedAuthority> authorities) {
        User user = new User(username,
                "robin", true, true, true, true, auths);
        return user;
    }
    
}

在这个类中，你就可以从数据库中读入用户的密码，角色信息，是否锁定，账号是否过期等，我想这么简单的代码就不再多解释了。



6.对于资源的访问权限的定义，我们通过实现FilterInvocationSecurityMetadataSource这个接口来初始化数据。

package com.robin.erp.fwk.security;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

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.security.web.util.AntUrlPathMatcher;
import org.springframework.security.web.util.UrlMatcher;
/**
 * 
 * 此类在初始化时，应该取到所有资源及其对应角色的定义
 * 
 * @author Robin
 * 
 */
public class MyInvocationSecurityMetadataSource
        implements FilterInvocationSecurityMetadataSource {
    private UrlMatcher urlMatcher = new AntUrlPathMatcher();;
    private static Map<String, Collection<ConfigAttribute>> resourceMap = null;

    public MyInvocationSecurityMetadataSource() {
        loadResourceDefine();
    }

    private void loadResourceDefine() {
        resourceMap = new HashMap<String, Collection<ConfigAttribute>>();
        Collection<ConfigAttribute> atts = new ArrayList<ConfigAttribute>();
        ConfigAttribute ca = new SecurityConfig("ROLE_ADMIN");
        atts.add(ca);
        resourceMap.put("/index.jsp", atts);
        resourceMap.put("/i.jsp", atts);
    }

    // According to a URL, Find out permission configuration of this URL.
    public Collection<ConfigAttribute> getAttributes(Object object)
            throws IllegalArgumentException {
        // guess object is a URL.
        String url = ((FilterInvocation)object).getRequestUrl();
        Iterator<String> ite = resourceMap.keySet().iterator();
        while (ite.hasNext()) {
            String resURL = ite.next();
            if (urlMatcher.pathMatchesUrl(url, resURL)) {
                return resourceMap.get(resURL);
            }
        }
        return null;
    }

    public boolean supports(Class<?> clazz) {
        return true;
    }
    
    public Collection<ConfigAttribute> getAllConfigAttributes() {
        return null;
    }

}

看看loadResourceDefine方法，我在这里，假定index.jsp和i.jsp这两个资源，需要ROLE_ADMIN角色的用户才能访问。

这个类中，还有一个最核心的地方，就是提供某个资源对应的权限定义，即getAttributes方法返回的结果。注意，我例子中使用的是AntUrlPathMatcher这个path matcher来检查URL是否与资源定义匹配，事实上你还要用正则的方式来匹配，或者自己实现一个matcher。



7.剩下的就是最终的决策了，make a decision

package com.robin.erp.fwk.security;
import java.util.Collection;
import java.util.Iterator;

import org.springframework.security.access.AccessDecisionManager;
import org.springframework.security.access.AccessDeniedException;
import org.springframework.security.access.ConfigAttribute;
import org.springframework.security.access.SecurityConfig;
import org.springframework.security.authentication.InsufficientAuthenticationException;
import org.springframework.security.core.Authentication;
import org.springframework.security.core.GrantedAuthority;


public class MyAccessDecisionManager implements AccessDecisionManager {

    //In this method, need to compare authentication with configAttributes.
    // 1, A object is a URL, a filter was find permission configuration by this URL, and pass to here.
    // 2, Check authentication has attribute in permission configuration (configAttributes)
    // 3, If not match corresponding authentication, throw a AccessDeniedException.
    public void decide(Authentication authentication, Object object,
            Collection<ConfigAttribute> configAttributes)
            throws AccessDeniedException, InsufficientAuthenticationException {
        if(configAttributes == null){
            return ;
        }
        System.out.println(object.toString());  //object is a URL.
        Iterator<ConfigAttribute> ite=configAttributes.iterator();
        while(ite.hasNext()){
            ConfigAttribute ca=ite.next();
            String needRole=((SecurityConfig)ca).getAttribute();
            for(GrantedAuthority ga:authentication.getAuthorities()){
                if(needRole.equals(ga.getAuthority())){  //ga is user's role.
                    return;
                }
            }
        }
        throw new AccessDeniedException("no right");
    }

    @Override
    public boolean supports(ConfigAttribute attribute) {
        // TODO Auto-generated method stub
        return true;
    }

    @Override
    public boolean supports(Class<?> clazz) {
        return true;
    }


}

在这个类中，最重要的是decide方法，如果不存在对该资源的定义，直接放行；否则，如果找到正确的角色，即认为拥有权限，并放行，否则throw new AccessDeniedException("no right");这样，就会进入上面提到的403.jsp页面。