Initial commit of the Python utility class

Author: pborissow

src/javaxt/express/utils/Python.java

@@ -0,0 +1,182 @@
+package javaxt.express.utils;
+
+import java.util.*;
+import javaxt.json.JSONObject;
+//import static javaxt.utils.Console.console;
+
+
+//******************************************************************************
+//**  Python
+//******************************************************************************
+/**
+ *   Used to execute python commands and parse the output.
+ *
+ ******************************************************************************/
+
+public class Python {
+
+    private String python;
+
+
+  //**************************************************************************
+  //** Constructor
+  //**************************************************************************
+    public Python(String pythonCommand){
+        try{
+            test(pythonCommand);
+            python = pythonCommand;
+        }
+        catch(Exception e){
+            throw new IllegalArgumentException("Invalid");
+        }
+    }
+
+
+  //**************************************************************************
+  //** Constructor
+  //**************************************************************************
+    public Python(){
+
+      //Check which python is installed on the system
+        for (String pythonCommand : new String[]{"python3", "python"}){
+            try{
+                test(pythonCommand);
+                python = pythonCommand;
+                break;
+            }
+            catch(Exception e){
+                //e.printStackTrace();
+            }
+        }
+
+        if (python==null) throw new IllegalArgumentException("Invalid");
+    }
+
+
+  //**************************************************************************
+  //** getScriptVersion
+  //**************************************************************************
+  /** Returns a version number for a given script. Under the hood, this method
+   *  simply passes "--version" as a command-line argument to the script and
+   *  returns the response.
+   */
+    public String getScriptVersion(javaxt.io.File script) throws Exception {
+        ArrayList<String> params = new ArrayList<>();
+        params.add("--version");
+        List<String> output = execute(script, params);
+        return output.get(0);
+    }
+
+
+  //**************************************************************************
+  //** executeScript
+  //**************************************************************************
+  /** Used to run a given python script. Assumes the script is implemented as
+   *  a command line application and that the application generates some sort
+   *  of JSON formatted response.
+   */
+    public JSONObject executeScript(javaxt.io.File script, ArrayList<String> params)
+    throws Exception {
+        return parseOutput(execute(script, params));
+    }
+
+
+  //**************************************************************************
+  //** execute
+  //**************************************************************************
+    private List<String> execute(javaxt.io.File script, ArrayList<String> params)
+    throws Exception {
+
+        String[] cmdarray = new String[params.size()+2];
+        cmdarray[0] = python;
+        cmdarray[1] = script.toString();
+        int i = 2;
+        for (String param : params){
+            cmdarray[i] = param;
+            i++;
+        }
+
+        javaxt.io.Shell cmd = new javaxt.io.Shell(cmdarray);
+        cmd.run();
+        List<String> output = cmd.getOutput();
+        List<String> errors = cmd.getErrors();
+
+
+      //Check if there are any errors
+        parseErrors(errors);
+
+
+      //Return output
+        return output;
+    }
+
+
+  //**************************************************************************
+  //** parseOutput
+  //**************************************************************************
+  /** Used to parse the standard output stream and return a JSONObject. Throws
+   *  an exception if the output can't be parsed.
+   */
+    private static JSONObject parseOutput(List<String> output) throws Exception {
+        try{
+
+            StringBuilder str = new StringBuilder();
+            Iterator<String> i2 = output.iterator();
+            while (i2.hasNext()){
+                String out = i2.next();
+                if (out!=null) str.append(out);
+            }
+
+            return new JSONObject(str.toString());
+        }
+        catch(Exception e){
+            StringBuilder err = new StringBuilder();
+            err.append("Error parsing script output");
+            StringBuilder result = new StringBuilder();
+            Iterator<String> i2 = output.iterator();
+            while (i2.hasNext()){
+                String out = i2.next();
+                if (out!=null) result.append(out + "\r\n");
+            }
+            err.append(":\r\n" + result);
+            throw new Exception(err.toString());
+        }
+    }
+
+
+  //**************************************************************************
+  //** parseErrors
+  //**************************************************************************
+  /** Used to parse the error output stream. Throws an exception if there are
+   *  any errors.
+   */
+    private static void parseErrors(List<String> errors) throws Exception{
+        if (errors.size()>0){
+            StringBuilder err = new StringBuilder();
+            Iterator<String> i2 = errors.iterator();
+            while (i2.hasNext()){
+                String error = i2.next();
+                if (error!=null) err.append(error + "\r\n");
+            }
+            if (err.length()>0){
+                throw new Exception(err.toString());
+            }
+        }
+    }
+
+
+  //**************************************************************************
+  //** test
+  //**************************************************************************
+  /** Used to test a given string to see if it is a valid "python" command.
+   */
+    private static void test(String python) throws Exception {
+        String[] cmdarray = new String[]{python, "--version"};
+        javaxt.io.Shell cmd = new javaxt.io.Shell(cmdarray);
+        cmd.run();
+        parseErrors(cmd.getErrors());
+
+        //TODO: check output
+        //console.log("Found python " + cmd.getOutput().get(0));
+    }
+}