通常在根据LDAP进行身份验证时会采取以下三种方法：

1、利用一个LDAP用户的用户名和密码绑定到LDAP服务器。

2、在LDAP中检索一个用户的条目，然后将提供的密码和检索到的LDAP记录中的密码属性相比较。

3、“两次绑定”验证方法。

基于LDAP进行身份验证，最好也是最通用的方法就是 “两次绑定”。这种方法的步骤以及优点可参看我的另一篇博客： 基于LDAP进行验证-方法和问题

当前Shiro只支持了第一种方法，即使用用户名和密码到LDAP服务器中进行绑定来判断合法性。

我自己写了一个认证类，实现了“两次绑定”验证。同时解决了目前做LDAP认证时没有区分错误情况，返回的错误提示信息不够准确的问题。

配置信息：

[main]
ldapRealm = main.java.name.peter.shiro.realm.ldap.LdapAuthenticator
ldapRealm.rootDN = dc=example,dc=com
ldapRealm.contextFactory.url = ldap://localhost:389
ldapRealm.contextFactory.systemUsername = cn=Manager,dc=example,dc=com
ldapRealm.contextFactory.systemPassword = secret

认证类：

/***
 * 基于Ldap进行身份认证,二次绑定方式.
 * 
 * @author wanghao
 * 
 */
public class LdapAuthenticator extends JndiLdapRealm {

private static final Logger log = LoggerFactory
.getLogger(LdapAuthenticator.class);
private String rootDN;

public LdapAuthenticator() {
super();
}

public String getRootDN() {
return rootDN;
}

public void setRootDN(String rootDN) {
this.rootDN = rootDN;
}

@Override
/***
 * 认证
 */
protected AuthenticationInfo doGetAuthenticationInfo(
AuthenticationToken token) throws AuthenticationException {
AuthenticationInfo info;
try {
info = queryForAuthenticationInfo(token, getContextFactory());
} catch (AuthenticationNotSupportedException e) {
String msg = "Unsupported configured authentication mechanism";
throw new UnsupportedAuthenticationMechanismException(msg, e);
} catch (javax.naming.AuthenticationException e) {
String msg = "LDAP authentication failed.";
throw new AuthenticationException(msg, e);
} catch (NamingException e) {
String msg = "LDAP naming error while attempting to authenticate user.";
throw new AuthenticationException(msg, e);
} catch (UnknownAccountException e) {
String msg = "UnknownAccountException";
throw new UnknownAccountException(msg, e);
} catch (IncorrectCredentialsException e) {
String msg = "IncorrectCredentialsException";
throw new IncorrectCredentialsException(msg, e);
}

return info;
}

@Override
protected AuthenticationInfo queryForAuthenticationInfo(
AuthenticationToken token, LdapContextFactory ldapContextFactory)
throws NamingException {

Object principal = token.getPrincipal();
Object credentials = token.getCredentials();

LdapContext systemCtx = null;
LdapContext ctx = null;
try {
systemCtx = ldapContextFactory.getSystemLdapContext();

SearchControls constraints = new SearchControls();
constraints.setSearchScope(SearchControls.SUBTREE_SCOPE);
NamingEnumeration results = systemCtx.search(rootDN, "cn="
+ principal, constraints);
if (results != null && !results.hasMore()) {
throw new UnknownAccountException();
} else {
while (results.hasMore()) {
SearchResult si = (SearchResult) results.next();
principal = si.getName() + "," + rootDN;
}
log.info("DN="+principal);
try {
ctx = ldapContextFactory.getLdapContext(principal,
credentials);
} catch (NamingException e) {
throw new IncorrectCredentialsException();
}
return createAuthenticationInfo(token, principal, credentials,
ctx);
}
} finally {
LdapUtils.closeContext(systemCtx);
LdapUtils.closeContext(ctx);
}
}
}