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Perfect processing of json data cannot perform success

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Release： 2018-04-25 14:56:38

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This time I will bring you the problems of perfect processing of json data that cannot execute success, and perfect json data that cannot execute success. What are the precautions?The following is a practical case, let's take a look.

1.jquery obtains json data through the ajax method and does not execute the success callback method

Problem description: jquery obtains json data through the ajax method and does not execute the success callback method

Cause of the problem: There is a problem with the json format or it does not conform to the standard writing method, resulting in the error callback method being always executed.

Solution: Make the json format must comply with the following three standard writing methods:

　1 ) Key name: enclosed in double quotes;

2) String : enclosed in double quotes;

3) Numbers and Boolean values do not need to use double quotes Brackets;

Note: Must be double brackets!

2. Ajax uses json in jQueryData typeAlways skip the success execution error statement

Execute the function

error : function(XMLHttpRequest, textStatus, errorThrown) {
//这个error函数调试时非常有用，如果解析不正确，将会弹出错误框
　　　　alert(XMLHttpRequest.responseText); 
alert(XMLHttpRequest.status);
alert(XMLHttpRequest.readyState);
alert(textStatus); // parser error;
}

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and you will understand the error message; the

pop-up box displays:

<!DOCTYPE html PUBLIC "-//W3C //DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD /xhtml1-transitional.dtd">以 及<?xml version="1.0" encoding="gb2312" ?>

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These two sentences, although I don’t know why, After I deleted it, success was successfully executed

3. When the URL in $.ajax() crosses domains, success is always not executed and an error is always entered

1) I added ServletActionContext.getResponse().setHeader("Access-Control-Allow-Origin", "*");

to solve cross-domain issues Question, you can successfully enter success

2) dataType: "json",

Remove it and see if you can enter success.

dataType is the type of information expected to be returned by the server.

Reason: The returned data type must conform to the defined data type. That is, if the dataType you define is of json type, then the returned data must be json, otherwise the program block in error will be executed.

(1) At the same time, special attention needs to be paid to whether the returned JSON data is in strict JSON format.

(2) You should also be seriously concerned when the background returns a List data (the items in the List When the data is in JSON format), if there is dirty data, it is not in strict JSON format.

I believe you have mastered the method after reading the case in this article. For more exciting information, please pay attention to other related articles on the php Chinese website!