esProc can process json data. Here we’ll introduce some of the applications through examples. 1. Analyzing and generating json data with esProc; 2. Data-interchange between esProc and application program through json; 3. Reading json file data in esProc.
A Analyzing and generating json data with esProc
Generally speaking, json is a format used by webpage js program and Java’s server-side program (such as servlet) to interchange data. While data access between Java’s server-side program and the databases adopts SQL result set format. esProc can act as an intermediary in the data computation and data-interchange between the two formats.
In this example, we use esProc to query detailed information of a group of designated employees. Both data input and output will adopt json format. Table employee of database demo contains all information of the employees:
esProc receives an EID list of json format and returns corresponding detailed information of employees in json format. The code is as follows:
1. esProc program test.dfx receives a parameter: jsonEID.
2. esProc completes json analysis, data processing and generates results in json format:
A1： Connect to database demo.
A2： Retrieve data from table employee.
A3： Use import@j function to parse the inputting jsonEID parameter (EID list in json format) and generate a table sequence containing only one field EID.
A4： Use align function to get from users data the employee information designated by A3.
A5： Convert employee information into json strings.
A6： Return employee information of json format.
B Interchanging json data between esProc and Java application
In the above example, esProc program is saved as test.dfx file to be called by Java application. Steps for calling the file are as follows:
1. Deploy esProc in Java application.
See esProc Tutorial for detail.
2. Call test.dfx in Java application.
Code example is as follows:
public void testDataServer(){
Connection con = null;
com.esproc.jdbc.InternalCStatementst;
try{
// Users id list in json format can be transmitted from browser-side to the program and converted into strings for use. Here process of receiving json data is omitted and value is assigned directly
String jsonEid="[{EID:8},{EID:32},{EID:44}]";
// Create a connection
Class.forName("com.esproc.jdbc.InternalDriver");
con= DriverManager.getConnection("jdbc:esproc:local://");
// Call stored procedure. test is the file name of dfx
st =(com.esproc.jdbc.InternalCStatement)con.prepareCall("call test(?)");
// Set parameters
st.setObject(1,jsonEid);
// Execute stored procedure
st.execute();
// Get result set
ResultSet set = st.getResultSet();
String jsonEmployee=null;
if (set.next()) jsonEmployee=set.getString(1);
// After getting detailed user information in json format, convert it into json objects and return them to browser-side. How to use jsonEmployee is omitted here
}
catch(Exception e){
System.out.println(e);
}
finally{
// Close the connection
if (con!=null) {
try {
con.close();
}
catch(Exception e) {
System.out.println(e);
}
}
}
}
C Reading and processing json file data in esProc
JSON file test.json contains information including class, serial number, names, subjects, scores, etc. Format is as follows:
[
{
"class": "Class one",
"id": 1,
"name": "Emily",
"subject": "English",
"score": 84
},
{
"class": "Class one",
"id": 1,
"name": "Emily",
"subject": "Math",
"score": 77
},
......
{
"class": "Class one",
"id": 7,
"name": "Nicholas",
"subject": "PE",
"score": 60
}
]
It is convenient for esProc to perform the reading and computation of JSON data. After that the result is submitted to Java application in the format of JDBC result set. Steps are as follows:
1. Developing esProc script
Use esProc editor to develop script (fromJSON.dfx), read the json file, analyze it and complete the computation:
A1： Use read() to read json file in string format;
A2： Use import@j() function to parse the json file into a table sequence;
A3： Group students ID and summarize the total scores in A4;
A5： Sort by total scores in descending order and return result set through result in A7
2. Java application calls fromJSON.dfx to present result.
Steps are omitted here for they are almost the same as those in the above example.