invoke()

Description:

Invoke the static function of class in the package.

Syntax:

invoke(p.c.f,a_i,…)

Note:

The function calls the static function f of class c in the package p, which can be omitted. Do not allow overload methods (with the same name but different signatures).

 

When invoking a user-defined function, you should put the user-defined function class file in the format of .class in the path [esProc install-root directory]/esProc/classes/{p}; if the user-defined function is used at the web side, then you should put the corresponding function in path WEB-INF/classes/{p}.

Parameter:

p	Package path
c	Class name
f	Static method name
ai	Parameter

The following lists data types of the parameters passed for the invoke() function and their corresponding parameter data types in Java classes:

Bool	java.lang.Boolean
Int	java.lang.Integer
Long	java.lang.Long
Float	java.lang.Double
Decimal	java.math.BigDecimal
Date	java.sql.Date
Time	java.sql.Time
Datetime	java.sql.Timerstamp
String	java.lang.String
Blob	byte []
Sequence	Object[]

Option:

@x	Convert the sequence type parameter or return value; can be performed recursively

Example:

I  Below is content of JAVA class api.Calc01:

package api;

public class Calc01 {

public static Double distance1(Number loc) {

double len = Math.abs(loc.doubleValue());

len = Math.round(len*1000)/1000d;

return Double.valueOf(len);

}

}

Place Calc01.class in path [esProc install-root directory]/esProc/classes/api and invoke function distance1 from the cellset file:

	A
1	-12.34567
2	=invoke(api.Calc01.distance1,A1)
3	=invoke(api.Calc01.distance1, -512)

The static method distance1 calculates the distance between a given point and the origin, with the result rounded to 3 decimal places. A method invoked in an esProc cellset file should be both static and public.

 

II  Create a customized class LineReaders for implementing the ILineInput interface so that users can retrieve a various types of data files using the file cursor. The file path can be defined as a parameter to be passed to the customized class. Then the file contents can be retrieved through stream in a row-wise fashion or by skipping certain individual rows; and the cursor can thus be closed in a certain way.

1. Below is a sample program:  

package api;

import java.io.BufferedReader;

import java.io.EOFException;

import java.io.File;

import java.io.FileInputStream;

import java.io.IOException;

import java.io.InputStreamReader;

import java.text.DateFormat;

import java.text.ParseException;

import java.text.SimpleDateFormat;

import com.scudata.dm.ILineInput;

import com.scudata.dm.UserUtils;

import com.scudata.dm.cursor.ICursor;

 

public class LineReaders implements ILineInput {

private String pathName;

private boolean hasTitle;

private BufferedReader bfr;

 

final String COL_SEP = "\t";

final String encoding = "UTF-8";

 

String lineTxt = null;

 

final DateFormat df = new SimpleDateFormat("yyyy-MM-dd ");

String[] rowData;

Object[] datas = new Object[3];

 

public LineReaders(String pathName,boolean hasTitle) {

this.pathName = pathName;

this.hasTitle=hasTitle;

}

 

public static LineReaders newInstance(String pathName,boolean hasTitle) {

return new LineReaders(pathName,hasTitle);

}

 

private BufferedReader getBufferedReader() throws IOException {

if (bfr == null) {

File file = new File(pathName);

if (file.isFile() && file.exists()) { // Check if the file exists

InputStreamReader read = new InputStreamReader(new FileInputStream(file), encoding);// Take the type of character encoding into consideration

bfr = new BufferedReader(read);

}

}

return bfr;

}

//Read an individual row

public Object[] readLine() throws IOException {  

   

BufferedReader bfr = getBufferedReader();

try {

if (!hasTitle) {

datas[0] = "ID";

datas[1] = "BirthDate";

datas[2] = "Name";

}

while ((lineTxt = bfr.readLine()) != null) {

rowData = lineTxt.split(COL_SEP);

if (rowData != null && rowData.length == 3) {

if (hasTitle) {

datas[0] = rowData[0];

datas[1] = rowData[1];

datas[2] = rowData[2];

hasTitle = false;

return datas;

}

datas[0] = Integer.parseInt(rowData[0]);

datas[1] = df.parse(rowData[1]);

datas[2] = rowData[2];

return datas;

}

}

return null;

} catch (EOFException e) {

return null;

} catch (ParseException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

return datas;

}

// Convert the ILineInput instance to a cursor

public static ICursor UserUtilsReader(String pathName,boolean hasTitle){

return UserUtils.newCursor(newInstance(pathName,hasTitle), "t");

}

//Skip an individual row

public boolean skipLine() throws IOException{

BufferedReader bfr = getBufferedReader();

try {     

String s = bfr.readLine();

if(s!=null){     

return true;

}

} catch (EOFException e) {

return false;

}   

return false;

}

//Close the cursor

public void close() throws IOException {

if (bfr != null) {

bfr.close();

bfr = null;

}

}

2. Place a LineReaders.class file in the api folder in the [esProc install-root directory]/esProc/classes path.

3. The contents of the file (it uses the character encoding of UTF-8) retrieved by a cursor are as follows:

4.  Invoke the customized function with invoke() function in the esProc cellset file:

	A
1	=invoke(api.LineReaders.UserUtilsReader,"D://abc.txt",true)	Call the customized function.
2	=A1.skip(3)	3
3	=A1.fetch()

III Using a sequence type parameter

package api;

 

public class Calc01 {

  public static int sum(Object []vals) {

      int result = 0;

      for(Object val : vals){

       result += ((Number)val).intValue();

       }

      return result;

      }

  public static Integer[] sum2(Object []vals){

    Integer []result = new Integer[vals.length];

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

      result[i] = sum((Object[])vals[i]);

    }

    return result;

  }

 

}

	A
1	[1,2,3,4]
2	=invoke@x(api.Calc01.sum,A1)	@x option converts the sequence type parameter; the static method sum accumulates members in A1’s sequence.
3	=invoke@x(api.Calc01.sum, to(100))	Calculates the cumulative sum from 1 to 100.
4	=invoke@x(api.Calc01.sum2,A1.(to(~)))	@x option converts the sequence type parameter, which is a sequence of sequences.