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This article mainly introduces "what is the method of JavaScript object annotation". In daily operation, I believe that many people have doubts about the method of JavaScript object annotation. The editor consulted all kinds of data and sorted out simple and easy-to-use operation methods. I hope it will be helpful to answer the doubts of "what is the method of JavaScript object annotation?" Next, please follow the editor to study!

JavaScript object dimensioning

In fact, most JavaScript objects are made up of associative arrays, numeric indexed arrays, strings, numbers, or nesting combinations of these types. Because all types can be declared directly with JavaScript, the object graph can be defined statically in a single statement.

Listing 7 declares an object using the JSON syntax and demonstrates how to access it. Curly braces represent associative arrays (that is, objects) whose key-value combinations are separated by commas. Square brackets indicate an array of numeric indexes.

Listing 7. Declare a simple object directly in JavaScript with JSON

Var band = {name: "The Beatles", members: [{name: "John", instruments: ["Vocals", "Guitar", "Piano"]}, {name: "Paul", instruments: ["Vocals", "Bass", "Piano", "Guitar"]}, {name: "George", instruments: ["Guitar", "Vocals"]}, {name: "Ringo", instruments: ["Drums", "Vocals"]}}; / / Interrogate the band objectvar musician = band.members [3] Alert (musician.name+ "played" + musician.instruments [0] + "with" + band.name)

Since JSON is an interesting language feature, what does it mean for Ajax? The beauty is that you can use JSON to send JavaScript object graphs over the network in Ajax server responses.

This means that you can avoid using clumsy DOM API to navigate XML on the client side-- you only need to analyze the JSON response and you immediately get an accessible JavaScript object graph. First, however, you need to turn JavaBean into JSON.

Generate JSON from the Java class

The advantages and disadvantages of different XML generation techniques are also applicable to the generation of JSON. And it can be proved that there is a need to use presentation template technology again. However, using JSON is conceptually closer to passing serialized objects between application layers than creating a view of application state.

I'll show you how to use the org.json Java API to create a toJSONObject () method on the Java class. You can then simply serialize the JSONObject into JSON. Listing 8 reflects the XML discussed in listing 1, showing the toJSONObject () implementation of the Order class.

Listing 8. ToJSONObject () method implementation of the Order class

Public JSONObject toJSONObject () {JSONObject json = new JSONObject (); json.put ("id", id); json.put ("cost", getFormattedCost ()); json.put ("date", date); JSONArray jsonItems = new JSONArray (); for (Iterator

As you can see, org.json API is very simple. JSONObject stands for JavaScript objects (that is, associative arrays) and has different put () methods, which accept String keys and values of primitive types, String types, or other JSON types.

JSONArray represents an indexed array, so its put () method accepts only one value. Notice in listing 8 that you create the jsonItems array and then attach it to the json object with put (); you can do this in another way by calling:

Json.accumulate ("items", iter.next (). ToJSONObject ())

The accumulate () method is similar to put (), except that it adds values to an indexed array identified by key. Listing 9 shows how to serialize JSONObject and write it to the servlet response.

Listing 9. Generate a serialized JSON response from JSONObject

Public void doGet (HttpServletRequest req, HttpServletResponse res) throws java.io.IOException, ServletException {String custId = req.getParameter ("username"); Customer customer = getCustomer (custId); res.setContentType ("application/x-json"); res.getWriter (). Print (customer.toJSONObject ());}

As you can see, it didn't actually do anything. The toString () method of JSONObject implicitly called here does all the work. Note that the application/x-json content type is still a little uncertain-at the time of this writing, there is no final conclusion as to what MIME type JSON should belong to. However, at present, application/x-json is a reasonable choice. Listing 10 shows a sample response from this servlet code.

Listing 10. JSON representation of Customer bean

{"orders": [{"items": [{"price": "$49.99", "description": "512 Megabyte Type 1 CompactFlash card. Manufactured by Oolong Industries "," name ":" Oolong 512MB CF Card "," id ":" iMur55768 "}, {" price ":" $299.99 "," description ":" 7.2 Megapixel digital camera featuring six shooting modes and 3x optical zoom. Silver. "," name ":" Fujak Superpix72 Camera "," id ":" iMur74491 "}]," date ":" 08-26-2005 "," cost ":" $349.98 "," id ":" Omur11123 "}]," realname ":" James Hyrax "," username ":" jimmy66 "} so far, the study of" what is the method of JavaScript object annotation "is over. I hope to solve everyone's doubts. The collocation of theory and practice can better help you learn, go and try it! If you want to continue to learn more related knowledge, please continue to follow the website, the editor will continue to work hard to bring you more practical articles!

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