尝试在servlet中获取数组时获取null

Question

I have a below set of code to get the table data in an array and pass the same to servlet through ajax call. But i am getting null. Please someone help me on what my mistake / how to get the required data since i am new to this servlet and web app. So far i tried with some examples given in SO. but i am clueless to get my expected data.

 var myTableArray = [];
        $("table#itemtable tr").each(function() { 
            var arrayOfThisRow = [];
            var tableData = $(this).find('td');
            if (tableData.length > 0) {
                tableData.each(function() { arrayOfThisRow.push($(this).text()); });
                myTableArray.push(arrayOfThisRow);
            }
        });

        alert(myTableArray); 
        $.ajax({
            url:"insertmasteritem",
            type:"POST",
            dataType:'json',
            data: {json:myTableArray},
            success:function(data){
                // codes....
           },
       });

Servlet code

String[] myJsonData = request.getParameterValues("json[]");
System.out.println("myJsonData.length"+myJsonData.length);

    for (int i = 0; i < myJsonData.length; i++) {

           String[] innerArray=myJsonData[i].split(",");  
           System.out.println(myJsonData[i]);
       }

Answer 1

Send your Json data like this

   $.ajax({
            url:"insertmasteritem",
            type:"POST",
            dataType:'json',
            data:myTableArray,
            success:function(data){
                // codes....
           },
   });

and In Servlet Class

JSONObject jsonObj= new JSONObject(request.getParameter("myTableArray"));
Iterator it = jsonObj.keys(); 

while(it.hasNext())
{
  String jsonKey = (String)it.next();
  String jsonValue = jsonObj.getString(jsonKey);
  System.out.println(jsonKey  + " --> " + jsonValue );
}

Answer 2

Well, you need to send a properly formatted JSON object (as a string) to the servlet. Possibly the easiest way to do this is to create some javascript objects and fill an array with these objects. The array data should then be converted to a JSON string (using JSON.stringify). I'm going to hardcode object values (but you will get them from your table)

Javascript code

function generateJson(){
  var myObjArr = [];
//you will typically have just one object (e.g. myObj, which you will fill  in your ajax table loop 
  //myObj.v1 = v1_val;
  //myObj.v2 = v2_val;
  ...
  //myObjArr[i] = myObj; //
  myObj1 = { "v1": "Orange", "v2": "ABC", "v3":10,"v4":"OK"  };
  myObj2 = { "v1": "Apple", "v2": "XYZ", "v3":25,"v4":"OK"  };

  myObjArr[0] = myObj1;
  myObjArr[1] = myObj2;

 var jsonObjStr = JSON.stringify(myObjArr);
 //you can now use jsonObjStr to send your data to the servlet
 // document.getElementById("json").innerHTML = jsonObjStr;//this is just added for testing purposes
 }

The generated JSON

[{"v1":"Orange","v2":"ABC","v3":10,"v4":"OK"},{"v1":"Apple","v2":"XYZ","v3":25,"v4":"OK"}]

As you can see, the json string starts with a [ (which denotes an array). You may have to change this to start with a { (and with a } ) depending on how your JSON parser works ({} denote an object).

For the servlet part, it depends on the actual JSON parser you're using. Try to use some of the suggestions provided by others. I can provide some code using Jackson though, but you will have to add the Jackson library to your classpath.

Answer 3

为什么将参数值作为JSON []

String[] myJsonData = request.getParameterValues("json[]");