ob-java.el: Add support for variables, return values, tramp

* lisp/ob-java.el: Add support for variables and return values.  Write
tempfiles to the `org-babel-temporary-directory'.  Make package,
class, and main method definitions optional.

* testing/lisp/test-ob-java.el: Add tests.

ob-java was missing features common to many other org-babel
implementations, such as the ability to accept variables and return a
value. This brings those features to ob-java, making the experience
more consistent across org-babel languages, and expanding the ways
java source blocks interact with org mode buffers.

A simple java program requires boilerplate code to declare a class and
main method.  This boilerplate code makes java source blocks more
tedious to write and more effort to read.  This is more evident in an
org buffer where there may be many small source blocks.  This change
makes that code optional.  If it is not provided, the source block
will be wrapped in the boilerplate code just before compilation.

Most org babel implementation write temporary files to the
`org-babel-temporary-directory'.  That avoids polluting the current
directory and provides built-in support for tramp.  ob-java would
write source files and binaries to the directory containing the org
file by default.  This may be unexpected and unwanted, and didn't work
with tramp.  This change writes all tempfiles to the
`org-babel-temporary-directory'.

Executing an ob-java source block would always try to compile and run
the code in the source block, so a source block that wasn't
runnable (didn't contain a main method) would error during run.  This
change adds a generic main method just before compilation if one isn't
included in the source block so that the run will succeed.

There were no tests for ob-java.  This adds tests.

lisp/ob-java.el

@@ -1,9 +1,8 @@
-;;; ob-java.el --- Babel Functions for Java          -*- lexical-binding: t; -*-
+;;; ob-java.el --- org-babel functions for java evaluation -*- lexical-binding: t -*-
 
 ;; Copyright (C) 2011-2020 Free Software Foundation, Inc.
 
-;; Author: Eric Schulte
-;; Maintainer: Ian Martins <ianxm@jhu.edu>
+;; Author: Ian Martins <ianxm@jhu.edu>
 ;; Keywords: literate programming, reproducible research
 ;; Homepage: https://orgmode.org
 
@@ -24,8 +23,7 @@
 
 ;;; Commentary:
 
-;; Currently this only supports the external compilation and execution
-;; of java code blocks (i.e., no session support).
+;; Org-Babel support for evaluating java source code.
 
 ;;; Code:
 (require 'ob)
@@ -33,52 +31,394 @@
 (defvar org-babel-tangle-lang-exts)
 (add-to-list 'org-babel-tangle-lang-exts '("java" . "java"))
 
-(defcustom org-babel-java-command "java"
-  "Name of the java command.
-May be either a command in the path, like java
-or an absolute path name, like /usr/local/bin/java
-parameters may be used, like java -verbose"
+(defvar org-babel-default-header-args:java '()
+  "Default header args for java source blocks.")
+
+(defconst org-babel-header-args:java '((imports . :any))
+  "Java-specific header arguments.")
+
+(defvar org-babel-java-compiler-command "javac"
+  "Name of the command to execute the java compiler.")
+
+(defvar org-babel-java-runtime-command "java"
+  "Name of the command to run the java runtime.")
+
+(defcustom org-babel-java-hline-to "null"
+  "Replace hlines in incoming tables with this when translating to java."
   :group 'org-babel
-  :version "24.3"
+  :version "25.2"
+  :package-version '(Org . "9.3")
   :type 'string)
 
-(defcustom org-babel-java-compiler "javac"
-  "Name of the java compiler.
-May be either a command in the path, like javac
-or an absolute path name, like /usr/local/bin/javac
-parameters may be used, like javac -verbose"
+(defcustom org-babel-java-null-to 'hline
+  "Replace `null' in java tables with this before returning."
   :group 'org-babel
-  :version "24.3"
-  :type 'string)
+  :version "25.2"
+  :package-version '(Org . "9.3")
+  :type 'symbol)
 
 (defun org-babel-execute:java (body params)
-  (let* ((classname (or (cdr (assq :classname params))
-			(error
-			 "Can't compile a java block without a classname")))
-	 (packagename (file-name-directory classname))
-	 (src-file (concat classname ".java"))
+  "Execute a java source block with BODY code and PARAMS params."
+  (let* (;; if true, run from babel temp directory
+         (run-from-temp (not (assq :dir params)))
+         ;; class and package
+         (fullclassname (or (cdr (assq :classname params))
+                            (org-babel-java-find-classname body)))
+         ;; just the class name
+         (classname (car (last (split-string fullclassname "\\."))))
+         ;; just the package name
+         (packagename (if (seq-contains fullclassname ?.)
+                          (file-name-base fullclassname)))
+         ;; the base dir that contains the top level package dir
+         (basedir (file-name-as-directory (if run-from-temp
+                                              org-babel-temporary-directory
+                                            ".")))
+         ;; the dir to write the source file
+         (packagedir (if (and (not run-from-temp) packagename)
+                         (file-name-as-directory
+                          (concat basedir (replace-regexp-in-string "\\\." "/" packagename)))
+                       basedir))
+         ;; the filename of the source file
+         (src-file (concat packagedir classname ".java"))
+	 ;; compiler flags
 	 (cmpflag (or (cdr (assq :cmpflag params)) ""))
-	 (cmdline (or (cdr (assq :cmdline params)) ""))
+	 ;; runtime flags
+         (cmdline (or (cdr (assq :cmdline params)) ""))
+         ;; command line args
 	 (cmdargs (or (cdr (assq :cmdargs params)) ""))
-	 (full-body (org-babel-expand-body:generic body params)))
+         ;; the command to compile and run
+         (cmd (concat org-babel-java-compiler-command " " cmpflag " "
+                      (org-babel-process-file-name src-file 'noquote)
+                      " && " org-babel-java-runtime-command
+                      " -cp " (org-babel-process-file-name basedir 'noquote)
+		      " " cmdline " " (if run-from-temp classname fullclassname)
+		      " " cmdargs))
+         ;; header args for result processing
+         (result-type (cdr (assq :result-type params)))
+         (result-params (cdr (assq :result-params params)))
+         (result-file (and (eq result-type 'value)
+                           (org-babel-temp-file "java-")))
+         ;; the expanded body of the source block
+         (full-body (org-babel-expand-body:java body params)))
+
     ;; created package-name directories if missing
-    (unless (or (not packagename) (file-exists-p packagename))
-      (make-directory packagename 'parents))
+    (unless (or (not packagedir) (file-exists-p packagedir))
+      (make-directory packagedir 'parents))
+
+    ;; write the source file
+    (setq full-body (org-babel-java--expand-for-evaluation
+		     full-body run-from-temp result-type result-file))
     (with-temp-file src-file (insert full-body))
-    (org-babel-eval
-     (concat org-babel-java-compiler " " cmpflag " " src-file) "")
-    (let ((results (org-babel-eval (concat org-babel-java-command
-                                           " " cmdline " " classname " " cmdargs) "")))
-      (org-babel-reassemble-table
-       (org-babel-result-cond (cdr (assq :result-params params))
-	 (org-babel-read results t)
-         (let ((tmp-file (org-babel-temp-file "c-")))
-           (with-temp-file tmp-file (insert results))
-           (org-babel-import-elisp-from-file tmp-file)))
-       (org-babel-pick-name
-        (cdr (assq :colname-names params)) (cdr (assq :colnames params)))
-       (org-babel-pick-name
-        (cdr (assq :rowname-names params)) (cdr (assq :rownames params)))))))
+
+    ;; compile, run, process result
+    (org-babel-reassemble-table
+     (org-babel-java-evaluate cmd result-type result-params result-file)
+     (org-babel-pick-name
+      (cdr (assoc :colname-names params)) (cdr (assoc :colnames params)))
+     (org-babel-pick-name
+      (cdr (assoc :rowname-names params)) (cdr (assoc :rownames params))))))
+
+;; helper functions
+
+(defun org-babel-java-find-classname (body)
+  "Try to find fully qualified class name in BODY.
+Look through BODY for the package and class.  If found, put them
+together into a fully qualified class name and return.  Else just
+return class name.  If that isn't found either, default to Main."
+  (let ((package (if (string-match "package \\\([^ ]*\\\);" body)
+                     (match-string 1 body)))
+        (class (if (string-match "public class \\\([^ \n]*\\\)" body)
+                   (match-string 1 body))))
+    (or (and package class (concat package "." class))
+        (and class class)
+        (and package (concat package ".Main"))
+        "Main")))
+
+(defconst org-babel-java--package-re "^[[:space:]]*package .*;$"
+  "Regexp for the package statement.")
+(defconst org-babel-java--imports-re "^[[:space:]]*import .*;$"
+  "Regexp for import statements.")
+(defconst org-babel-java--class-re "^public class [[:alnum:]_]+[[:space:]]*\n?[[:space:]]*{"
+  "Regexp for the class declaration.")
+(defconst org-babel-java--main-re "public static void main(String\\(?:\\[]\\)? args\\(?:\\[]\\)?).*\n?[[:space:]]*{"
+  "Regexp for the main method declaration.")
+(defconst org-babel-java--any-method-re "public .*(.*).*\n?[[:space:]]*{"
+  "Regexp for any method.")
+(defconst org-babel-java--result-wrapper "\n    public static String __toString(Object val) {
+        if (val instanceof String) {
+            return \"\\\"\" + val + \"\\\"\";
+        } else if (val == null) {
+            return \"null\";
+        } else if (val.getClass().isArray()) {
+            StringBuffer sb = new StringBuffer();
+            Object[] vals = (Object[])val;
+            sb.append(\"[\");
+            for (int ii=0; ii<vals.length; ii++) {
+                sb.append(__toString(vals[ii]));
+                if (ii<vals.length-1)
+                    sb.append(\",\");
+            }
+            sb.append(\"]\");
+            return sb.toString();
+        } else if (val instanceof List) {
+            StringBuffer sb = new StringBuffer();
+            List vals = (List)val;
+            sb.append(\"[\");
+            for (int ii=0; ii<vals.size(); ii++) {
+                sb.append(__toString(vals.get(ii)));
+                if (ii<vals.size()-1)
+                    sb.append(\",\");
+            }
+            sb.append(\"]\");
+            return sb.toString();
+        } else {
+            return String.valueOf(val);
+        }
+    }
+
+    public static void main(String[] args) throws IOException {
+        BufferedWriter output = new BufferedWriter(new FileWriter(\"%s\"));
+        output.write(__toString(_main(args)));
+        output.close();
+    }"
+  "Code to inject into a class so that we can capture the value it returns.
+This implementation was inspired by ob-python, although not as
+elegant.  This modified the source block to write out the value
+it wants to return to a temporary file so that ob-java can read
+it back.  The name of the temporary file to write must be
+replaced in this string.")
+
+(defun org-babel-java--expand-for-evaluation (body suppress-package-p result-type result-file)
+  "Expand source block for evaluation.
+In order to return a value we have to add a __toString method.
+In order to prevent classes without main methods from erroring we
+add a dummy main method if one is not provided.  These
+manipulations are done outside of `org-babel--expand-body' so
+that they are hidden from tangles.
+
+BODY is the file content before instrumentation.
+
+SUPPRESS-PACKAGE-P if true, suppress the package statement.
+
+RESULT-TYPE is taken from params.
+
+RESULT-FILE is the temp file to write the result."
+  (with-temp-buffer
+    (insert body)
+
+    ;; suppress package statement
+    (goto-char (point-min))
+    (when (and suppress-package-p
+	       (re-search-forward org-babel-java--package-re nil t))
+      (replace-match ""))
+
+    ;; add a dummy main method if needed
+    (goto-char (point-min))
+    (when (not (re-search-forward org-babel-java--main-re nil t))
+      (org-babel-java--move-past org-babel-java--class-re)
+      (insert "\n    public static void main(String[] args) {
+        System.out.print(\"success\");
+}\n\n"))
+
+    ;; special handling to return value
+    (when (eq result-type 'value)
+      (goto-char (point-min))
+      (org-babel-java--move-past org-babel-java--class-re)
+      (insert (format org-babel-java--result-wrapper
+		      (org-babel-process-file-name result-file 'noquote)))
+      (search-forward "public static void main(") ; rename existing main
+      (replace-match "public static Object _main("))
+
+    ;; add imports
+    (org-babel-java--import-maybe "java.util" "List")
+    (org-babel-java--import-maybe "java.util" "Arrays")
+    (org-babel-java--import-maybe "java.io" "BufferedWriter")
+    (org-babel-java--import-maybe "java.io" "FileWriter")
+    (org-babel-java--import-maybe "java.io" "IOException")
+
+    (buffer-string)))
+
+(defun org-babel-java--move-past (re)
+  "Move point past the first occurrence of the given regexp RE."
+  (while (re-search-forward re nil t)
+    (goto-char (1+ (match-end 0)))))
+
+(defun org-babel-java--import-maybe (package class)
+  "Import from PACKAGE the given CLASS if it is used and not already imported."
+  (let (class-found import-found)
+    (goto-char (point-min))
+    (setq class-found (re-search-forward class nil t))
+    (goto-char (point-min))
+    (setq import-found (re-search-forward (concat "^import .*" package ".*" class ";") nil t))
+    (when (and class-found (not import-found))
+      (org-babel-java--move-past org-babel-java--package-re)
+      (insert (concat "import " package "." class ";\n")))))
+
+(defun org-babel-expand-body:java (body params)
+  "Expand BODY with PARAMS.
+BODY could be a few statements, or could include a full class
+definition specifying package, imports, and class.  Because we
+allow this flexibility in what the source block can contain, it
+is simplest to expand the code block from the inside out."
+  (let* ((fullclassname (or (cdr (assq :classname params)) ; class and package
+                            (org-babel-java-find-classname body)))
+         (classname (car (last (split-string fullclassname "\\.")))) ; just class name
+         (packagename (if (seq-contains fullclassname ?.)  ; just package name
+                          (file-name-base fullclassname)))
+         (var-lines (org-babel-variable-assignments:java params))
+         (imports-val (assq :imports params))
+         (imports (if imports-val
+                      (split-string (org-babel-read (cdr imports-val) nil) " ")
+                    nil)))
+    (with-temp-buffer
+      (insert body)
+
+      ;; wrap main.  If there are methods defined, but no main method
+      ;; and no class, wrap everything in a generic main method.
+      (goto-char (point-min))
+      (when (and (not (re-search-forward org-babel-java--class-re nil t))
+                 (not (re-search-forward org-babel-java--any-method-re nil t)))
+        (org-babel-java--move-past org-babel-java--package-re) ; if package is defined, move past it
+        (org-babel-java--move-past org-babel-java--imports-re) ; if imports are defined, move past them
+        (insert "public static void main(String[] args) {\n")
+        (indent-code-rigidly (point) (point-max) 4)
+        (goto-char (point-max))
+        (insert "\n}"))
+
+      ;; wrap class.  If there's no class, wrap everything in a
+      ;; generic class.
+      (goto-char (point-min))
+      (when (not (re-search-forward org-babel-java--class-re nil t))
+        (org-babel-java--move-past org-babel-java--package-re) ; if package is defined, move past it
+        (org-babel-java--move-past org-babel-java--imports-re) ; if imports are defined, move past them
+        (insert (concat "\npublic class " (file-name-base classname) " {\n"))
+        (indent-code-rigidly (point) (point-max) 4)
+        (goto-char (point-max))
+        (insert "\n}"))
+      (goto-char (point-min))
+
+      ;; insert variables from source block headers
+      (when var-lines
+        (goto-char (point-min))
+        (org-babel-java--move-past org-babel-java--class-re)   ; move inside class
+        (insert (mapconcat 'identity var-lines "\n"))
+        (insert "\n"))
+
+      ;; add imports from source block headers
+      (when imports
+        (goto-char (point-min))
+        (org-babel-java--move-past org-babel-java--package-re) ; if package is defined, move past it
+        (insert (mapconcat (lambda (package) (concat "import " package ";")) imports "\n") "\n"))
+
+      ;; add package at the top
+      (goto-char (point-min))
+      (when (and packagename (not (re-search-forward org-babel-java--package-re nil t)))
+        (insert (concat "package " packagename ";\n")))
+
+      ;; return expanded body
+      (buffer-string))))
+
+(defun org-babel-variable-assignments:java (params)
+  "Return a list of java statements assigning the block's variables.
+variables are contained in PARAMS."
+  (mapcar
+   (lambda (pair)
+     (let* ((type-data (org-babel-java-val-to-type (cdr pair)))
+            (basetype (car type-data))
+            (var-to-java (lambda (var) (funcall #'org-babel-java-var-to-java var basetype))))
+       (format "    static %s %s = %s;"
+               (cdr type-data)                     ; type
+               (car pair)                          ; name
+               (funcall var-to-java (cdr pair))))) ; value
+   (org-babel--get-vars params)))
+
+(defun org-babel-java-var-to-java (var basetype)
+  "Convert an elisp value to a java variable.
+Convert an elisp value, VAR, of type BASETYPE into a string of
+java source code specifying a variable of the same value."
+  (cond ((and (sequencep var) (not (stringp var)))
+         (let ((var-to-java (lambda (var) (funcall #'org-babel-java-var-to-java var basetype))))
+           (concat "Arrays.asList(" (mapconcat var-to-java var ", ") ")")))
+        ((eq var 'hline) org-babel-java-hline-to)
+        ((eq basetype 'integerp) (format "%d" var))
+        ((eq basetype 'floatp) (format "%f" var))
+        ((eq basetype 'stringp) (if (and (stringp var) (string-match-p ".\n+." var))
+                                    (error "Java does not support multiline string literals")
+                                  (format "\"%s\"" var)))))
+
+(defun org-babel-java-val-to-type (val)
+  "Determine the type of VAL.
+Return (BASETYPE . LISTTYPE), where BASETYPE is a symbol
+representing the type of the individual items in VAL, and
+LISTTYPE is a string name of the type parameter for a container
+for BASETYPE items."
+  (let* ((basetype (org-babel-java-val-to-base-type val))
+         (basetype-str (pcase basetype
+                         (`integerp "Integer")
+                         (`floatp "Double")
+                         (`stringp "String")
+                         (_ (error "Unknown type %S" basetype)))))
+    (cond
+     ((and (listp val) (listp (car val))) ; a table
+      (cons basetype (format "List<List<%s>>" basetype-str)))
+     ((or (listp val) (vectorp val))      ; a list declared in the source block header
+      (cons basetype (format "List<%s>" basetype-str)))
+     (t                                   ; return base type
+      (cons basetype basetype-str)))))
+
+(defun org-babel-java-val-to-base-type (val)
+  "Determine the base type of VAL.
+VAL may be
+`integerp' if all base values are integers
+`floatp' if all base values are either floating points or integers
+`stringp' otherwise."
+  (cond
+   ((integerp val) 'integerp)
+   ((floatp val) 'floatp)
+   ((or (listp val) (vectorp val))
+    (let ((type nil))
+      (mapc (lambda (v)
+              (pcase (org-babel-java-val-to-base-type v)
+                (`stringp (setq type 'stringp))
+                (`floatp
+                 (when (or (not type) (eq type 'integerp))
+                   (setq type 'floatp)))
+                (`integerp
+                 (unless type (setq type 'integerp)))))
+            val)
+      type))
+   (t 'stringp)))
+
+(defun org-babel-java-table-or-string (results)
+  "Convert RESULTS into an appropriate elisp value.
+If the results look like a list or vector, then convert them into an
+Emacs-lisp table, otherwise return the results as a string."
+  (let ((res (org-babel-script-escape results)))
+    (if (listp res)
+        (mapcar (lambda (el) (if (eq 'null el)
+                                 org-babel-java-null-to
+                               el))
+                res)
+      res)))
+
+(defun org-babel-java-evaluate (cmd result-type result-params result-file)
+  "Evaluate using an external java process.
+CMD the command to execute.
+
+If RESULT-TYPE equals 'output then return standard output as a
+string.  If RESULT-TYPE equals 'value then return the value
+returned by the source block, as elisp.
+
+RESULT-PARAMS input params used to format the reponse.
+
+RESULT-FILE filename of the tempfile to store the returned value in
+for 'value RESULT-TYPE.  Not used for 'output RESULT-TYPE."
+  (let ((raw (pcase result-type
+               ('output (org-babel-eval cmd ""))
+               ('value (org-babel-eval cmd "")
+                       (org-babel-eval-read-file result-file)))))
+    (org-babel-result-cond result-params raw
+      (org-babel-java-table-or-string raw))))
 
 (provide 'ob-java)
 

testing/lisp/test-ob-java.el

@@ -0,0 +1,583 @@
+;;; test-ob-java.el --- tests for ob-java.el
+
+;; Copyright (c) 2020 Ian Martins
+;; Authors: Ian Martins
+
+;; This file is not part of GNU Emacs.
+
+;; This program is free software; you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; This program is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+;;; Code:
+(require 'org-test)
+
+(require 'ob-core)
+(defvar org-babel-temporary-directory ; from ob-core
+  (if (boundp 'org-babel-temporary-directory)
+    org-babel-temporary-directory
+  (temporary-file-directory)))
+
+(org-test-for-executable "java")
+(org-test-for-executable "javac")
+(unless (featurep 'ob-java)
+  (signal 'missing-test-dependency "Support for java code blocks"))
+
+; simple tests
+
+(ert-deftest ob-java/simple ()
+  "Hello world program that writes output."
+  (org-test-with-temp-text
+      "#+begin_src java :results output silent
+System.out.print(42);
+#+end_src"
+   (should (string= "42" (org-babel-execute-src-block)))))
+
+(ert-deftest ob-java/simple-with-bracket ()
+  "Hello world program that outputs an open square bracket."
+  (org-test-with-temp-text
+      "#+begin_src java :results output silent
+System.out.print(\"[42\");
+#+end_src"
+   (should (string= "[42" (org-babel-execute-src-block)))))
+
+(ert-deftest ob-java/simple-with-quote ()
+  "Hello world program that writes quotes."
+  (org-test-with-temp-text
+      "#+begin_src java :results output silent
+System.out.print(\"\\\"42\\\"\");
+#+end_src"
+   (should (string= "\"42\"" (org-babel-execute-src-block)))))
+
+(ert-deftest ob-java/simple-return-int ()
+  "Hello world program that returns an int value."
+  (org-test-with-temp-text
+      "#+begin_src java :results silent
+return 42;
+#+end_src"
+   (should (eq 42 (org-babel-execute-src-block)))))
+
+(ert-deftest ob-java/simple-return-float ()
+  "Hello world program that returns a float value."
+  (org-test-with-temp-text
+      "#+begin_src java :results silent
+return 42.0;
+#+end_src"
+   (should (equal 42.0 (org-babel-execute-src-block)))))
+
+(ert-deftest ob-java/simple-return-string ()
+  "Hello world program that returns a string value."
+  (org-test-with-temp-text
+      "#+begin_src java :results silent
+return \"forty two\";
+#+end_src"
+    (should (string= "forty two" (org-babel-execute-src-block)))))
+
+(ert-deftest ob-java/simple-with-main ()
+  "Hello world program that defines a main function."
+  (org-test-with-temp-text
+      "#+begin_src java :results output silent
+public static void main(String[] args) {
+    System.out.print(42);
+}
+#+end_src"
+    (should (string= "42" (org-babel-execute-src-block)))))
+
+(ert-deftest ob-java/simple-with-two-methods ()
+  "Hello world program with two methods and no class."
+  (org-test-with-temp-text
+      "#+begin_src java :results output silent
+public static void main(String[] args) {
+    System.out.print(foo());
+}
+public static int foo() {
+    return 42;
+}
+#+end_src"
+    (should (string= "42" (org-babel-execute-src-block)))))
+
+(ert-deftest ob-java/simple-with-no-main ()
+  "Hello world program with no main method.  Babel adds a dummy one so it can run without error."
+  (org-test-with-temp-text
+      "#+begin_src java :results output silent
+public static int foo() {
+    return 42;
+}
+#+end_src"
+    (should (string= "success" (org-babel-execute-src-block)))))
+
+(ert-deftest ob-java/simple-with-main-args-array ()
+  "Hello world program that defines a main function with the square brackets after `args'."
+  (org-test-with-temp-text
+      "#+begin_src java :results output silent
+public static void main(String args[]) {
+    System.out.print(42);
+}
+#+end_src"
+    (should (string= "42" (org-babel-execute-src-block)))))
+
+(ert-deftest ob-java/simple-with-class ()
+  "Hello world program that defines a class."
+  (org-test-with-temp-text
+      "#+begin_src java :results output silent
+public class Simple {
+    public static void main(String[] args) {
+        System.out.print(42);
+    }
+}
+#+end_src"
+   (should (string= "42" (org-babel-execute-src-block)))))
+
+(ert-deftest ob-java/simple-with-class-and-package ()
+  "Hello world program that defines a class and package."
+  (org-test-with-temp-text
+      "#+begin_src java :results output silent
+package pkg;
+public class Simple {
+    public static void main(String[] args) {
+        System.out.print(42);
+    }
+}
+#+end_src"
+    (should (string= "42" (org-babel-execute-src-block)))))
+
+(ert-deftest ob-java/simple-with-class-attr ()
+  "Hello world program with class header attribute."
+  (org-test-with-temp-text
+      "#+begin_src java :results output silent :classname Simple
+public static void main(String[] args) {
+    System.out.print(42);
+}
+#+end_src"
+   (should (string= "42" (org-babel-execute-src-block)))))
+
+(ert-deftest ob-java/simple-with-class-attr-with-package ()
+  "Hello world program with class attr with package."
+  (org-test-with-temp-text
+      "#+begin_src java :results output silent :classname pkg.Simple
+public static void main(String[] args) {
+    System.out.print(42);
+}
+#+end_src"
+    (should (string= "42" (org-babel-execute-src-block)))))
+
+
+(ert-deftest ob-java/one-arg ()
+  "Command line arg."
+  (org-test-with-temp-text
+      "#+begin_src java :results output silent :cmdargs \"fortytwo\"
+System.out.print(args[0]);
+#+end_src"
+    (should (string= "fortytwo" (org-babel-execute-src-block)))))
+
+(ert-deftest ob-java/args-quoted-string ()
+  "Two command line args, first contains a space."
+  (org-test-with-temp-text
+      "#+begin_src java :results output silent :cmdargs \"\\\"forty two\\\" 42\"
+System.out.println(args[0]);
+System.out.println(args[1]);
+#+end_src"
+    (should (string= "forty two\n42\n" (org-babel-execute-src-block)))))
+
+;; var tests
+
+(ert-deftest ob-java/integer-var ()
+  "Read and write an integer variable."
+  (org-test-with-temp-text
+      "#+begin_src java :var a=42 :results output silent
+System.out.print(a);
+#+end_src"
+    (should (string= "42" (org-babel-execute-src-block)))))
+
+(ert-deftest ob-java/var-with-main ()
+  "Read and write an integer variable, with main function provided."
+  (org-test-with-temp-text
+      "#+begin_src java :var a=42 :results output silent
+public static void main(String[] args) {
+    System.out.print(a);
+}
+#+end_src"
+    (should (string= "42" (org-babel-execute-src-block)))))
+
+(ert-deftest ob-java/var-with-class ()
+  "Read and write an integer variable, with class provided."
+  (org-test-with-temp-text
+      "#+begin_src java :var a=42 :results output silent
+public class Main {
+    public static void main(String[] args) {
+        System.out.print(a);
+    }
+}
+#+end_src"
+    (should (string= "42" (org-babel-execute-src-block)))))
+
+(ert-deftest ob-java/var-with-class-and-package ()
+  "Read and write an integer variable, with class and package provided."
+  (org-test-with-temp-text
+      "#+begin_src java :var a=42 :results output silent
+package pkg;
+public class Main {
+    public static void main(String[] args) {
+        System.out.print(a);
+    }
+}
+#+end_src"
+    (should (string= "42" (org-babel-execute-src-block)))))
+
+(ert-deftest ob-java/var-with-class-and-hanging-curlies ()
+  "Read and write an integer variable, with class with hanging curlies."
+  (org-test-with-temp-text
+      "#+begin_src java :var a=42 :results output silent
+public class Main
+{
+    public static void main(String[] args)
+    {
+        System.out.print(a);
+    }
+}
+#+end_src"
+    (should (string= "42" (org-babel-execute-src-block)))))
+
+(ert-deftest ob-java/two-vars ()
+  "Read two integer variables, combine and write them."
+  (org-test-with-temp-text
+      "#+begin_src java :var a=21 b=2 :results output silent
+System.out.print(a*b);
+#+end_src"
+    (should (string= "42" (org-babel-execute-src-block)))))
+
+(ert-deftest ob-java/string-var ()
+  "Read and write a string variable."
+  (org-test-with-temp-text
+      "#+begin_src java :var a=\"forty two\" :results output silent
+System.out.print(String.format(\"%s, len=%d\", a, a.length()));
+#+end_src"
+    (should (string= "forty two, len=9" (org-babel-execute-src-block)))))
+
+(ert-deftest ob-java/multiline-string-var ()
+  "Java doesn't support multiline string literals, so this errors."
+  (org-test-with-temp-text
+      "#+begin_src java :var a=\"forty\ntwo\" :results output silent
+System.out.print(String.format(\"%s, len=%d\", a, a.length()));
+#+end_src"
+    (should-error (org-babel-execute-src-block)))
+  :type 'error)
+
+;; return list
+
+(ert-deftest ob-java/return-vector-using-list ()
+  "Return a vector using a list."
+  (org-test-with-temp-text
+      "#+begin_src java :results vector silent
+import java.util.List;
+import java.util.Arrays;
+List<List<Integer>> a = Arrays.asList(Arrays.asList(4),
+                                      Arrays.asList(2));
+return a;
+#+end_src"
+    (should (equal '((4) (2))
+                   (org-babel-execute-src-block)))))
+
+(ert-deftest ob-java/return-vector-using-array ()
+  "Return a vector using an array."
+  (org-test-with-temp-text
+      "#+begin_src java :results vector silent
+Integer[][] a = {{4}, {2}};
+return a;
+#+end_src"
+    (should (equal '((4) (2))
+                   (org-babel-execute-src-block)))))
+
+(ert-deftest ob-java/read-return-list ()
+  "Read and return a list."
+  (org-test-with-temp-text
+      "#+begin_src java :var a=java_list :results silent
+import java.util.List;
+import java.util.Arrays;
+List<String> b = Arrays.asList(a.get(0).get(0),
+                               a.get(1).get(0));
+return b;
+#+end_src
+
+#+name: java_list
+- forty
+- two"
+    (should (equal '("forty" "two")
+                   (org-babel-execute-src-block)))))
+
+(ert-deftest ob-java/read-list-return-array ()
+  "Read a list and return an array."
+  (org-test-with-temp-text
+      "#+begin_src java :var a=java_list :results silent
+String[] b = {a.get(0).get(0), a.get(1).get(0)};
+return b;
+#+end_src
+
+#+name: java_list
+- forty
+- two"
+    (should (equal '("forty" "two")
+                   (org-babel-execute-src-block)))))
+
+(ert-deftest ob-java/read-return-list-with-package ()
+  "Return a vector."
+  (org-test-with-temp-text
+      "#+begin_src java :var a=java_list :results silent
+package pkg;
+import java.util.List;
+import java.util.Arrays;
+List<String> b = Arrays.asList(a.get(0).get(0),
+                               a.get(1).get(0));
+return b;
+#+end_src
+
+#+name: java_list
+- forty
+- two"
+    (should (equal '("forty" "two")
+                   (org-babel-execute-src-block)))))
+
+(ert-deftest ob-java/output-list-with-spaces ()
+  "Return a vector."
+  (org-test-with-temp-text
+      "#+begin_src java :results output list raw silent
+System.out.println(\"forty two\");
+System.out.println(\"forty two\");
+#+end_src"
+    (should (equal "forty two\nforty two\n"
+                   (org-babel-execute-src-block)))))
+
+;; list vars
+
+(ert-deftest ob-java/list-var ()
+  "Read and write a list variable."
+  (org-test-with-temp-text
+      "#+begin_src java :var a='(\"forty\" \"two\") :results silent
+import java.util.List;
+List<String> b = a;
+return b;
+#+end_src"
+    (should (equal '("forty" "two")
+                   (org-babel-execute-src-block)))))
+
+(ert-deftest ob-java/vector-var ()
+  "Read and write a vector variable."
+  (org-test-with-temp-text
+      "#+begin_src java :var a='[\"forty\" \"two\"] :results silent
+import java.util.List;
+List<String> b = a;
+return b;
+#+end_src"
+    (should (equal '("forty" "two")
+                   (org-babel-execute-src-block)))))
+
+(ert-deftest ob-java/matrix-var ()
+  "Read and write matrix variable."
+  (org-test-with-temp-text
+      "#+begin_src java :var a=java_matrix :results silent
+import java.util.List;
+import java.util.Arrays;
+List<List<Integer>> b = Arrays.asList(Arrays.asList(a.get(0).get(0), a.get(1).get(0)),
+                                      Arrays.asList(a.get(0).get(1), a.get(1).get(1)));
+return b; // transpose
+#+end_src
+
+#+name: java_matrix
+| 2 | 1 |
+| 4 | 2 |"
+    (should (equal '((2 4) (1 2))
+                   (org-babel-execute-src-block)))))
+
+(ert-deftest ob-java/matrix-var-with-header ()
+  "Read matrix variable and write it with header."
+  (org-test-with-temp-text
+      "#+begin_src java :var a=java_matrix :results value table silent
+import java.util.List;
+import java.util.Arrays;
+List<List> b = Arrays.asList(Arrays.asList(\"col1\", \"col2\"),
+                                     null,
+                                     Arrays.asList(a.get(0).get(0), a.get(1).get(0)),
+                                     Arrays.asList(a.get(0).get(1), a.get(1).get(1)));
+return b; // transpose
+#+end_src
+
+#+name: java_matrix
+| 2 | 1 |
+| 4 | 2 |"
+    (should (equal '(("col1" "col2") hline (2 4) (1 2))
+                   (org-babel-execute-src-block)))))
+
+;; output table
+
+(ert-deftest ob-java/output-table-with-header ()
+  "Write a table that includes a header."
+  (org-test-with-temp-text
+      "#+begin_src java :var a=java_matrix :results output raw table silent
+System.out.println(\"|col1|col2|\");
+System.out.println(\"|-\");
+for (int ii=0; ii<a.size(); ii++) {
+    for (int jj=0; jj<a.get(0).size(); jj++) {
+        System.out.print(\"|\" + a.get(ii).get(jj));
+    }
+    System.out.println(\"\");
+ }
+#+end_src
+
+#+name: java_matrix
+| 2 | 1 |
+| 4 | 2 |"
+    (should (equal "|col1|col2|\n|-\n|2|1\n|4|2\n"
+                   (org-babel-execute-src-block)))))
+
+(ert-deftest ob-java/inhomogeneous_table ()
+  "Read and write an inhomogeneous table."
+  (org-test-with-temp-text
+      "#+begin_src java :var a=java_table :results silent
+import java.util.List;
+import java.util.Arrays;
+List<List> b = Arrays.asList(Arrays.asList(a.get(0).get(0),
+                                           Integer.parseInt(a.get(0).get(1))*2),
+                             Arrays.asList(a.get(1).get(0),
+                                           Integer.parseInt(a.get(1).get(1))*2));
+return b;
+#+end_src
+
+#+name: java_table
+  | string | number |
+  |--------+--------|
+  | forty  |      2 |
+  | two    |      1 |"
+   (should (equal
+            '(("forty" 4) ("two" 2))
+            (org-babel-execute-src-block)))))
+
+;; imports
+
+(ert-deftest ob-java/import_library ()
+  "Import a standard java library."
+  (org-test-with-temp-text
+      "#+begin_src java :results output silent :imports java.util.Base64
+byte[] encoded = Base64.getEncoder().encode(\"42\".getBytes());
+String decoded = new String(Base64.getDecoder().decode(encoded));
+System.out.print(String.format(\"encoded=%s, decoded=%s\", new String(encoded), decoded));
+#+end_src"
+   (should (string=
+            "encoded=NDI=, decoded=42"
+            (org-babel-execute-src-block)))))
+
+(ert-deftest ob-java/import_library_inline ()
+  "Import a standard java library."
+  (org-test-with-temp-text
+      "#+begin_src java :results output silent
+import java.util.Base64;
+byte[] encoded = Base64.getEncoder().encode(\"42\".getBytes());
+String decoded = new String(Base64.getDecoder().decode(encoded));
+System.out.print(String.format(\"encoded=%s, decoded=%s\", new String(encoded), decoded));
+#+end_src"
+   (should (string=
+            "encoded=NDI=, decoded=42"
+            (org-babel-execute-src-block)))))
+
+;; tangle
+
+(ert-deftest ob-java/tangle ()
+  "Tangle a source block."
+  (org-test-with-temp-text-in-file
+      "#+begin_src java :tangle \"Tangle.java\" :results value :classname Tangle
+return \"tangled\";
+#+end_src"
+    (should
+     (string=
+      "public class Tangle {
+    public static void main(String[] args) {
+        return \"tangled\";
+    }
+}
+"
+      (unwind-protect
+          (progn (org-babel-tangle)
+                 (with-temp-buffer
+                   (insert-file-contents "Tangle.java")
+                   (untabify (point-min) (point-max))
+                   (buffer-string)))
+        (delete-file "Tangle.java"))))))
+
+(ert-deftest ob-java/tangle-with-package ()
+  "Tangle a source block."
+  (org-test-with-temp-text-in-file
+      "#+begin_src java :tangle \"tangle/Tangle.java\" :results value :classname tangle.Tangle
+return \"tangled\";
+#+end_src"
+    (should
+     (string=
+      "package tangle;
+
+public class Tangle {
+    public static void main(String[] args) {
+        return \"tangled\";
+    }
+}
+"
+      (unwind-protect
+          (progn
+            (make-directory "tangle")
+            (org-babel-tangle)
+            (with-temp-buffer
+              (insert-file-contents "tangle/Tangle.java")
+              (untabify (point-min) (point-max))
+              (buffer-string)))
+        (delete-file "tangle/Tangle.java")
+        (delete-directory "tangle"))))))
+
+
+;; specify output dir
+
+(ert-deftest ob-java/simple-dir ()
+  "Hello world program that writes output."
+  (org-test-with-temp-text
+      (format  "#+begin_src java :results output silent :dir %s
+System.out.print(42);
+#+end_src" org-babel-temporary-directory)
+    (should (string=
+             "42"
+             (unwind-protect
+                 (org-babel-execute-src-block)
+               (delete-file (concat (file-name-as-directory org-babel-temporary-directory)
+                                    "Main.java"))
+               (delete-file (concat (file-name-as-directory org-babel-temporary-directory)
+                                    "Main.class")))))))
+
+(ert-deftest ob-java/simple-dir-with-package ()
+  "Hello world program that writes output."
+  (org-test-with-temp-text
+      (format "#+begin_src java :results output silent :dir %s
+package pkg;
+
+public class Main {
+    public static void main(String[] args) {
+      System.out.print(42);
+    }
+}
+#+end_src" org-babel-temporary-directory)
+    (should (string=
+             "42"
+             (unwind-protect
+                 (org-babel-execute-src-block)
+               (delete-file (concat (file-name-as-directory org-babel-temporary-directory)
+                                    "pkg/Main.java"))
+               (delete-file (concat (file-name-as-directory org-babel-temporary-directory)
+                                    "pkg/Main.class"))
+               (delete-directory (concat (file-name-as-directory org-babel-temporary-directory)
+                                         "pkg")))))))
+
+
+;;; test-ob-java.el ends here