Puzzling about JsonView

[mophisoft]

I'm not good at English, I wish I could describe the problem clear.

When we use Ext.JsonView, we usually write codes as follows:

// Example from Ext API

var tpl = new Ext.Template(
'<div class="entry">' +
'<a class="entry-title" href="{link}">{title}</a>' +
"<h4>{date} by {author} | {comments} Comments</h4>{description}" +
"</div><hr />"
);

var moreView = new Ext.JsonView("entry-list", tpl, {
jsonRoot: "posts"
});
moreView.on("beforerender", this.sortEntries, this);
moreView.load({
url:"/blog/get-posts.php",
params: "allposts=true",
text:"Loading Blog Entries..."
});

It really can get datas from specific url, but I want to get data with java object, and the object return a list which collect any other java objects such as java beans. How to achieve it?

[mophisoft]

Why doesn't anyone answer me? Doesn't anyone know the problem, or don't I make myself clear?

[aconran]

If I read this correctly you are asking how to convert a java object to JSON...

I'm guessing the reason you haven't any response is because these forums really aren't focused on the server-side languages as much as the client-side javascript. Your best bet is to probably ask on a Java forum or perhaps change the topic of this thread so that someone would be able to find it.

[PFM]

mophisoft,

If indeed you are asking about converting java objects to JSON (and also from JSON to java objects) take a look at the java classes at http://www.json.org/java/index.html

In the example below I use a JsonReader but it illustrates how to generate the JSON from java objects to return in the ajax response.

For my java dto objects, I include the following methods,



public String toJSON() {

try {
return toJSONObject().toString();
}
catch (Exception e) {
LOGGER.debug("toJSON exception\n" + e);
return null;
}
}

public JSONObject toJSONObject() {

try {
JSONObject jsonObject = new JSONObject();
jsonObject.put("feedId", feedId);
jsonObject.put("name", name);
jsonObject.put("description", description);
jsonObject.put("category", description.trim() + " - " + name.trim());
jsonObject.put("url", url);
jsonObject.put("httpProxyConfiguration", httpProxyConfiguration);
jsonObject.put("isActive", isActive);
jsonObject.put("lastUpdateDateTime", lastUpdateDateTime);
jsonObject.put("lastUpdateUser", lastUpdateUser);

return jsonObject;
}
catch (Exception e) {
LOGGER.error("toJSON exception\n" + e);
return null;
}
}



Example of servlet/Struts action using the JSON java classes... This example returns a list of records to be load



List list = feedService.listFeed();
if (list.size() == 0) {
JSONUtil.buildJSONResponse(printWriter, StatusCode.SC_LIST_EMPTY);
return null;
}

JSONReader jsonReader = new JSONReader();
for (Iterator iterator = list.iterator(); iterator.hasNext();) {
FeedDto feedDto = (FeedDto)iterator.next();
jsonReader.put(feedDto.toJSONObject());
}
JSONUtil.buildJSONDataResponse(printWriter, jsonReader);


Custom JSONReader.java to wrap JSON for Ext JSON reader format



public class JSONReader extends JSONArray {

Integer recordCount = null;

public JSONReader() {
super();
}

public JSONReader(Integer recordCount) {
this();
this.recordCount = recordCount;
}

public String toString() {

StringBuffer sb = new StringBuffer();
if (recordCount != null) {
sb.append("{\"recordCount\":" + recordCount.toString() + ",\"rows\":");
}
else {
sb.append("{\"recordCount\":" + this.length() + ",\"rows\":");
}
sb.append(super.toString());
sb.append("}");
return sb.toString();
}

}


Helper method to build AJAX response



public static void buildJSONDataResponse(PrintWriter printWriter, JSONReader jsonReader, String message) throws Exception {

JSONDataResponse jsonDataResponse = new JSONDataResponse();
jsonDataResponse.setStatusCode(StatusCode.SC_OK);
jsonDataResponse.setMessage(message);
jsonDataResponse.setData(jsonReader.toString());
if (LOGGER.isDebugEnabled()) {
LOGGER.debug(jsonDataResponse.toJSON());
}
printWriter.write(jsonDataResponse.toJSON());

}



Ext record and datastore using JsonReader



var recordLayout = [
{name: 'feedId', mapping: 'feedId'},
{name: 'name', mapping: 'name', type: 'string'},
{name: 'description', mapping: 'description', type: 'string'},
{name: 'category', mapping: 'category', type: 'string'},
{name: 'url', mapping: 'url', type: 'string'},
{name: 'httpProxyConfiguration', mapping: 'httpProxyConfiguration', type: 'string'},
{name: 'isActive', mapping: 'isActive', type: 'bool'},
{name: 'lastUpdateDateTime', mapping: 'lastUpdateDateTime'},
{name: 'lastUpdateUser', mapping: 'lastUpdateUser', type: 'string'}
];

feedRecord = Ext.data.Record.create(recordLayout);
var dataStore = {
reader: new Ext.data.JsonReader({
totalProperty: "recordCount",
root: "rows",
id: "feedTreeId"
}, feedRecord)
};

feedDataStore = new Ext.data.Store(dataStore);


Handling the AJAX response



var result = Ext.util.JSON.decode(o.responseText);
if (result.statusCode == StatusCode.SC_SUCCESS) {
var data = Ext.util.JSON.decode(result.data);
feedDataStore.loadData(data, false);
return;
}
else if (result.statusCode == StatusCode.SC_LIST_EMPTY) {
return;
}
else {
showAlert(result);
return;
}

Hopefully this is what you are looking for...

[mophisoft]

Zealous PFM, I'm extremely grateful to you, you make me known more details about json, it's also what I wanted. But your codes only had application in Ext.data.Store, my original intentions were apply them to Ext.JsonView, because I don't known how to use the 'url' in JsonView to connect a servlet/Struts action. The url seems only get datas/records through a link such as php, jsp, or asp.

[PFM]

mophisoft,

I have not used the JsonView. but just looking at it I would think that to go to a servlet/struts action would be no problem.



// direct load of JSON data
view.load("MyServlet...");


moreView.load({
url:"MyStrutsAction.do",
params: "allposts=true",
text:"Loading Blog Entries..."
});


And if you see the request in the servlet and build a JSON response, but the JsonView is not being updated, then I would look at the format of the JSON to make sure that it is correct.

Sorry I cannot be of anymore help with the JsonView, or if I misunderstood what your problem is... Maybe post the JS code you are trying and any JSON you are producing.

[Ronaldo]

PFM, thanks for that extensive explanation!
I think it's valuable enough to put it as a 'manual' in the learning section...

[fangzhouxing]

where is the code of JSONDataResponse?

[august]

where is the code of JSONDataResponse?

I also want to get the code of JSONDataResponse,and i am now on the json&ext project.

[herrjj]

Hi,

Thanks for the examples. This thread is a bit stale but if anyone has some insights I could use a bit of help.

How exactly is the DataReader being fed the JSON values loaded into the JSONReader array? I see that the jsonReader collection is populated with all the Beans returned by the service.

Normally, I might use request.setAttribute in order to make Java entities available to the JSP. Are you using this to then feed the values to Javascript code? If so, how?

Thanks!