Suppressing/handling errors from a sling:include - aem

Question

I have a SlingServlet that implements a JSON query service (very similar to the AEM Query Builder servlet). It creates a SyntheticResource to respond with a JSP "view", which is the JSON to be served. This JSP uses a to include each result object, which are cq:Page nodes.
When the tries to include a node which can not be rendered, it results in a 400 error, but in a peculiar way. The error appears first, followed by the expected JSON (which is malformed, because the value that could not be included is missing). I am able to override the 400 error text, so as to return "null", but I can not get the error to appear inline.
Consider:
response.api.json.jsp
{
"metadata": {
"page": ${pageIndex},
},
"data": [
<%
String[] results = (String[])slingRequest.getAttribute("results");
int i = 0;
if (results != null) {
for (String path : results) {
if (i > 0) {
%>
,
<%
}
%>
<sling:include path="<%=path%>"/>
<%
i++;
}
}
%>
]
}
the current response
<400.jsp error message up here>
{
"metadata": {
"page": 0,
},
"data": [
, // <- failed to include the path
{
"key1": , // <- failed to include the value string/object/etc
"key2": "value2"
}
]
}
the expected response
{
"metadata": {
"page": 0,
},
"data": [
<400.jsp error message>, // <- failed to include the path
{
"key1": <400.jsp error message>, // <- failed to include the value string/object/etc
"key2": "value2"
}
]
}
the expected response (assuming 400.jsp contains only "null")
{
"metadata": {
"page": 0,
},
"data": [
null, // <- failed to include the path
{
"key1": null, // <- failed to include the value string/object/etc
"key2": "value2"
}
]
}
Is there any way to get the error page (400.jsp) to appear inline, so that I can return null?
More info
response.api.json.jsp (main "view" for the service response)
{
"metadata": {
"page": ${pageIndex},
},
"data": [
<%
String[] results = (String[])slingRequest.getAttribute("results");
int i = 0;
if (results != null) {
for (String path : results) {
if (i > 0) {
%>
,
<%
}
%>
<sling:include path="<%=path%>"/>
<%
i++;
}
}
%>
]
}
page/api.json.jsp (data[] nodes included by the response.api.json.jsp)
{
"uid": <%=getFormattedString("jcr:uuid", properties)%>,
"pageTitle": <sling:include path="pageTitle"/>, // text component
"body": <sling:include path="body"/> // parsys component
}
text/api.json.jsp (pageTitle node included by each page/api.json.jsp)
{
"text": <%=getFormattedString("text", properties)%>,
"lastModified": <%=getFormattedDate("jcr:lastModified", properties)%>,
"resourceType": <%=getFormattedString("sling:resourceType", properties)%>
}
parsys/api.json.jsp (body node included by each page/api.json.jsp)
{
"resourceType": "${properties['sling:resourceType']}",
"children": [
<%
NodeIterator children = currentNode.getNodes();
int i = 0;
if (children != null && children.getSize() > 0) {
while (children.hasNext()) {
Node child = children.nextNode();
if (i > 0) {
%>
,
<%
}
%>
<sling:include path="<%=child.getPath()%>"/> // any component resource type
<%
i++;
}
}
%>
]
}

Answer 1

Don't use sling:include to get content from the paths, this will raise some recursion selector error. You should read the message node from the paths to get appropriate content value for your json. Here is an example. You can replace "/content/geometrixx-outdoors/en/women/jcr:content/par/banner" with your path.
<%# include file="/libs/foundation/global.jsp" %>
<%# page session="false" import="org.apache.sling.api.resource.Resource" %>
<%# page session="false" import="javax.jcr.Node" %>
<%
String yourMessage = "";
try {
Resource rs = resourceResolver.getResource("/content/geometrixx-outdoors/en/women/jcr:content/par/banner");
if (rs != null) {
Node node = rs.adaptTo(Node.class);
if (node.hasProperty("yourContentNode")) {
yourMessage = node.getProperty("yourContentNode").getString();
}
}
} catch (Exception e) {
}
%>
{
"metadata": {
"page": 1,
},
"data": [
<%= yourMessage %>,
{
"key1": "value 1",
"key2": "value2"
}
]
}