JNDI-LDAP 分页 [英] JNDI-LDAP paging

问题描述

我设法使分页像 here.问题是我需要公开一个如下所示的 API:getUsers(pageSize, pageNumber)，这与 JNDI/LDAP 进行分页的方式并不相符(使用您传递的 cookie每次到搜索方法).代码如下所示:

I managed to get pagination working like described here. The problem is I need to expose an API which would look like this:getUsers(pageSize, pageNumber), which does not really go well with the way JNDI/LDAP does the paging(with a cookie you pass each time to the search method). The code looks like this:

private NamingEnumeration ldapPagedSearch(String filter, int pageSize, int pageNumber){
    InitialLdapContext ctx = getInitialContext();

    //TODO: get the id also, need to spec it in UI
    // Create the search controls
    SearchControls searchCtls = new SearchControls();
    searchCtls.setSearchScope(SearchControls.SUBTREE_SCOPE);

    //keep a session
    byte[] cookie = null;

    //Request the paged results control
    Control[] ctls = new Control[]{new PagedResultsControl(pageSize, true)};
    ctx.setRequestControls(ctls);

    //Specify the search scope
    NamingEnumeration results = null;
    int currentPage = 1;
    do {
        results = ctx.search(getConfiguration().get(BASEDN_KEY), filter, searchCtls);

        //we got to the right page, return this page
        if(currentPage == pageNumber) {
            return results;
        }

        // loop through this page, because we cannot get a proper cookie otherwise
        // WARN: this could be a problem of performance
        while (results.hasMore()) results.next();

        // examine the paged results control response
        Control[] controls = ctx.getResponseControls();
        if (controls != null) {
            for (Control control : controls) {
                if (control instanceof PagedResultsResponseControl) {
                    cookie = ((PagedResultsResponseControl) control).getCookie();
                } 
            }
        }

        // pass the cookie back to the server for the next page
        ctx.setRequestControls(new Control[]{new PagedResultsControl(pageSize, cookie, Control.CRITICAL) });

        //increment page
        currentPage++;
    } while (cookie != null);


    ctx.close();

    //if we get here, means it is an empty set(consumed by the inner loop)
    return results;
}

看来我需要遍历所有页面才能获得所需的页面.此外，我需要遍历页面上的所有条目，才能获得下一页.

It seems I need to iterate through all the pages to get the required page. Moreover, I need to iterate through all the entries on a page, to be able to get the next page.

有没有更好的方法?我担心性能问题.

Is there a better way? I worry about performance issues.

推荐答案

有一种叫做虚拟列表视图"的东西.控制.它由几个 LDAP 服务器支持.不确定实现是否仍在 JNDI 中.如果没有，您可以考虑自己实现它.您必须将它与服务器端排序一起使用.

There is something called "Virtual List View" control. It is supported by a couple of LDAP servers. Not sure if the implementation is still in the JNDI. If not, you may consider to implement it yourself. You have to use it together with server side sorting.

另请参阅https://datatracker.ietf.org/doc/html/draft-ietf-ldapext-ldapv3-vlv-04 和http://www.cs.rit.edu/usr/local/pub/jeh/rit/java/lib/doc/ldapcontrols/com/sun/jndi/ldap/ctl/VirtualListViewControl.html

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