Sling Request Invocation Chain
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Implementing Sling Filters
Registration of Filters
- Standard Servlet Filter (javax.servlet.Filter)
- Need to be registered as Service („manually“ or SlingFilter SCR Annotation)
- Order and FilterScopes can be defined
- Order defined by Serviceranking
- Filterscopes
- REQUEST
- COMPONENT
- ERROR
- INCLUDE *
- FORWARD *
* FilterChain executes COMPONENT scope for these scopes as well.
SCR Annotation
@SlingFilter(scope = SlingFilterScope.COMPONENT, order = -10000, metatype = false) public class MyComponentFilter implements javax.servlet.Filter { @Override public void doFilter(ServletRequest pRequest, ServletResponse pResponse, FilterChain pChain) throws IOException, ServletException { // Implement Filter // continue with filter chaining pChain.doFilter(pRequest, pResponse); } } |
Filter Order
Existing Filters might use the deprecated “filter.order” instead “service.ranking”.
Existing Filters and their execution ORDER can be inspected via http://<instance>:<port>/system/console/status-slingfilter
Check Filterconditions at first place
public void doFilter(ServletRequest pRequest, ServletResponse pResponse, FilterChain pChain) throws IOException, ServletException { if (!(pRequest instanceof SlingHttpServletRequest)) { throw new ServletException("Request is not a Sling HTTP request."); } if (isFilterEnabled(slingRequest)) { // Implement Filter-Logic } else { // continue with filter chaining pChain.doFilter(pRequest, pResponse); } } |
Check available Information from slingRequest if Filter should do anything.
Be aware that these checks may be performed a lot especially for COMPONENT scope
Accessing and Using Data in Filter
if (isFilterEnabled(slingRequest)) { if (isFilterEnabled(slingRequest)) { Resource resource = slingRequest.getResource(); // already resolved if (null != resource) { PrintWriter writer = pResponse.getWriter(); writer.write("<component resourceType=\"" + resource.getResourceType() + "\">"); pChain.doFilter(pRequest, pResponse); writer.write("</component>"); return; } } } |