I'm developing javafx-project in clojure, but I cannot use these javafx's class : javafx.scene.layout.Hbox, javafx.scene.control.Label and javafx.scene.control.[something without Buttom].
I couldn't find solution of it.
Thank you!
Here is the code
temp/core.clj
```
(ns temp.core
(:import (javafx.application Application)
(javafx.scene.text Text Font FontWeight)
(javafx.scene.control Label TextField PasswordField Button)
(javafx.scene.layout GridPane HBox)
(javafx.scene.paint Color)
(javafx.geometry Pos Insets)
(javafx.event EventHandler)
(javafx.stage Stage))
(:gen-class))
(def x (Label. "Hello"))
;; get message
;; 2. Unhandled clojure.lang.Compiler$CompilerException
;; 1. Caused by java.lang.NoClassDefFoundError
;; javafx.scene.control.Labeled
(def H (HBox. 8))
;; get message
;; 1. Unhandled java.lang.IllegalArgumentException
;; No matching ctor found for class javafx.scene.layout.HBox
```
project.clj
(defproject temp "0.1.0-SNAPSHOT"
:description "FIXME: write description"
:url "http://example.com/FIXME"
:license {:name "Eclipse Public License"
:url "http://www.eclipse.org/legal/epl-v10.html"}
:dependencies [[org.clojure/clojure "1.8.0"]]
:main temp.core
:aot [temp.core]
:target-path "target/%s"
:profiles {:uberjar {:aot :all}})
I may find solution (I don't know why this solution is correct attribution)
Here is the solution
(ns temp.core
(:import (javafx.application Application)
(javafx.scene.text Text Font FontWeight)
(javafx.scene.control Label TextField PasswordField Button)
(javafx.scene.layout GridPane HBox)
(javafx.scene.paint Color)
(javafx.geometry Pos Insets)
(javafx.event EventHandler)
(javafx.stage Stage))
(:gen-class))
(defn x [] (Label. "Hello"))
(defn H [] (HBox. 8))
;; return error in 'lein run' :
;; java.lang.IllegalArgumentException: No matching ctor found for class
;; javafx.scene.layout.HBox
please tell me why this solution works correctly
There is a little more that you have to do in terms of initializing the JavaFX run-time system and starting it up. Here's a very small project that does so.
Here's a project file for Leiningen. It is not significantly different from what you have.
(defproject fxdemo "0.1.0-SNAPSHOT"
:description "FIXME: write description"
:url "http://example.com/FIXME"
:license {:name "Eclipse Public License"
:url "http://www.eclipse.org/legal/epl-v10.html"}
:dependencies [[org.clojure/clojure "1.8.0"]]
:aot :all
:main fxdemo.core)
And a very small program that just shows the version of the JavaFX subsystem.
(ns fxdemo.core
(:gen-class
:extends javafx.application.Application)
(:import (javafx.application Application)
(javafx.scene.layout HBox)
(javafx.scene.control Label)
(javafx.scene Scene)
(javafx.stage Stage)))
(defn -start
"Build the application interface and start it all up. Called by the
JavaFX runtime."
[this stage]
(let [ver (System/getProperty "javafx.runtime.version")
lbl (Label. (str "JavaFX Version: " ver))
root (HBox.)
scene (Scene. root 250 150)]
(.add (.getChildren root) lbl)
(doto ^Stage stage
(.setScene scene)
(.setTitle "fxdemo")
(.show))))
(defn -main
"Start up the GUI part of the application."
[& args]
(Application/launch fxdemo.core args))
On my system, executing lein run brings up this window:
You can't really use the pieces of the framework, like HBox and Label independently of the framework. If you look at the (gen-class... statement, you need your main program to extend the JavaFX Application class. To initialize the JavaFX subsystem, you need to use the Application/launch... method, usually in you program entry function, as shown. (There are exceptions and other ways to do this, but they are too complicated to explain here. This is the easiest/safest way to do it.) By the time the -start method is called by the JavaFX subsystem, things are mostly initialized and ready to go.
Also, notice the hyphen character, "-", preceding the main and start function names, these are needed as part of the interop between Java and Clojure.
I have a folder structure like this:
resources
a
b
x.txt
c
x.txt
I've created my runnable jar with lein uberjar.
When running my jar, I want to list the subfolders of a.
I know I can get the contents of resources/a/b/x.txt using clojure.java.io
(slurp (clojure.java.io/resource "a/b/x.txt"))
But I can't find a simple way to list the subfolders.
(clojure.java.io/file (clojure.java.io/resource "a")) just results in a java.lang.IllegalArgumentException: Not a file because it isn't a file, it's a resource inside the jar file.
Is there a library that does this?
here is the port of code from the java specific answer:
(ns my-project.core
(:require [clojure.string :as cs])
(:import java.util.zip.ZipInputStream)
(:gen-class))
(defrecord HELPER [])
(defn get-code-location []
(when-let [src (.getCodeSource (.getProtectionDomain HELPER))]
(.getLocation src)))
(defn list-zip-contents [zip-location]
(with-open [zip-stream (ZipInputStream. (.openStream zip-location))]
(loop [dirs []]
(if-let [entry (.getNextEntry zip-stream)]
(recur (conj dirs (.getName entry)))
dirs))))
(defn -main [& args]
(println (some->> (get-code-location)
list-zip-contents
(filter #(cs/starts-with? % "a/")))))
Being put to a main namespace and run with jar will output all the paths in the /resources/a folder..
java -jar ./target/my-project-0.1.0-SNAPSHOT-standalone.jar
;;=> (a/ a/b/ a/b/222.txt a/222.txt)
Also some quick research lead me to this library:
https://github.com/ronmamo/reflections
it shortens the code, but also requires some dependencies for the project (i guess it could be undesirable):
[org.reflections/reflections "0.9.11"]
[javax.servlet/servlet-api "2.5"]
[com.google.guava/guava "23.0"]
and the code is something like this:
(ns my-project.core
(:require [clojure.string :as cs])
(:import java.util.zip.ZipInputStream
[org.reflections
Reflections
scanners.ResourcesScanner
scanners.Scanner
util.ClasspathHelper
util.ConfigurationBuilder])
(:gen-class))
(defn -main [& args]
(let [conf (doto (ConfigurationBuilder.)
(.setScanners (into-array Scanner [(ResourcesScanner.)]))
(.setUrls (ClasspathHelper/forClassLoader (make-array ClassLoader 0))))]
(println
(filter #(cs/starts-with? % "a/")
(.getResources (Reflections. conf) #".*")))))
A different approach (but I must admit that it doesn't feel entirely satisfactory) is to read the contents at compile time. Assuming you have a function list-files that gives you the list from your project root directory:
(defmacro compile-time-filelist []
`'~(list-files "resources/a"))
or
(defmacro compile-time-filelist []
(vec (list-files "resources/a")))
You can recursively list all items in a dir using file-seq function. Example:
(let [files (file-seq (clojure.java.io/file "resources"))
dir? #(.isDirectory %)]
(map dir? files))
You can also call .listFiles or .list on a File object. The first gives file objects, the second gives filenames.
You can find additional examples here and here.
I ran lein new app hm, then in hm/src/hm edited core.clj to be:
(ns hm.core
(:gen-class)
(:use [hm.hashmap]))
(defn -main []
(def j (new hm.hashmap))
(-add j "foo" "bar")
(println j))
and hashmap.clj to be:
(ns hm.hashmap
(:gen-class
:methods [[hashmap [] java.util.HashMap]
[add [String String]]]))
(defn -hashmap []
(def h (new java.util.HashMap))
h)
(defn -add [this key value]
(. this put key value)
this)
The goal is to make a wrapper around the HashMap so I can understand Clojure and how it ties with Java. I'm fairly new to Clojure. However, when I compile this, I get a lot of ClassNotFoundException in hashmap.clj. How can I make this work?
Note: This is a direct answer to your question. I don't recommend that you learn Clojure this way.
You need to compile your classes before you can run them. In your project.clj add this to the map:
:aot [hm.hashmap]
Then you need to run lein compile in order to compile the classes. You should see output saying the hm.hashmap class was compiled. After that run lein run to invoke the "main "function in hm.core.
I removed the :methods part of your gen-class because you're already defining them below, and that was causing the weird java.lang., error. You're going to run into other errors, but this should be enough to get you passed this issue.
Your code has some other issues, but the immediate problem here is that the signature of add is incomplete. Your add returns this, a hm.hashmap.
To fix, change the signature to return an Object, or, with additional edit, a java.util.HashMap. If you want this to work as otherwise written, you'll also need to extend rather than encapsulate.
(ns hm.hashmap
(:gen-class
:extends java.util.HashMap
:methods [[add [String String] java.util.HashMap]]))
Finally change -main in core.clj to call the method using .add instead of trying to access the private -add.
...
(.add j "foo" "bar")
...
Then
lein clean
lein compile hm.core hm.hashmap
lein run
should print
#<hashmap {foo=bar}>
Note that you cannot, as far as I know, specify returning an hm.hashmap in the signature due to the timing of the symbol resolution. See GC Issue 81: compile gen-class fail when class returns self.
I am using Leiningen and Clojure and for the life of me I can't understand why Clojure makes it so difficult just to import namespaces correctly. This is the following error
This is what I have in my core.clj file:
; namespace macro
(ns animals.core
(:require animals.animal)
(:use animals.animal)
(:import (animals.animal Dog))
(:import (animals.animal Human))
(:import (animals.animal Arthropod))
(:import (animals.animal Insect)))
; make-animals will create a vector of animal objects
(defn make-animals []
(conj []
(Dog. "Terrier" "Canis lupis familiaris")
(Human. "Human" "Homo sapiens")
(Arthropod. "Brown Recluse" "Loxosceles reclusa")
(Insect. "Fire Ant" "Solenopsis conjurata")))
; print-animals will print all the animal objects
(defn print-animals [animals]
(doseq [animal animals]
(println animal)))
; move-animals will call the move action on each animal
(defn move-animals [animals]
(doseq [animal animals]
(animals.animal/move animal)))
; entry to main program
(defn -main [& args]
(let [animals make-animals]
(do
(println "Welcome to Animals!")
(println "-------------------")
(print-animals animals))))
Then, at the REPL, I enter the following (in the src/ directory of the lein project):
user> (require 'animals.core)
nil
user> (animals.core/-main)
ClassNotFoundException animals.core java.net.URLClassLoader$1.run (URLClassLoader.java:202)
Okay... what? Why?
For reference, here is my file animal.clj also in the animals directory:
(ns animals.animal)
(defprotocol Animal
"A simple protocol for animal behaviors."
(move [this] "Method to move."))
(defrecord Dog [name species]
Animal
(move [this] (str "The " (:name this) " walks on all fours.")))
(defrecord Human [name species]
Animal
(move [this] (str "The " (:name this) " walks on two legs.")))
(defrecord Arthropod [name species]
Animal
(move [this] (str "The " (:name this) " walks on eight legs.")))
(defrecord Insect [name species]
Animal
(move [this] (str "The " (:name this) " walks on six legs.")))
With your code pasted into a fresh Leiningen project, I get a different error due to a typo in -main: (let [animals make-animals] ...) should be (let [animals (make-animals)] ...). With this change, it all works fine:
user=> (require 'animals.core)
nil
user=> (animals.core/-main)
Welcome to Animals!
-------------------
#animals.animal.Dog{:name Terrier, :species Canis lupis familiaris}
#animals.animal.Human{:name Human, :species Homo sapiens}
#animals.animal.Arthropod{:name Brown Recluse, :species Loxosceles reclusa}
#animals.animal.Insect{:name Fire Ant, :species Solenopsis conjurata}
nil
Incidentally, it doesn't matter where exactly you invoke lein repl from as long as it's somewhere inside the project directory.
I'd venture a guess that there was something the matter with your namespace when you first tried to require it and now it won't load due to some namespace loading state in your REPL. You might want to try (require :reload 'animals.core) and if that doesn't work, restart your REPL. (You could also paste your entire REPL interaction up to the ClassNotFoundException somewhere if you run into it again.)
Also, about your ns form:
You shouldn't both :require and :use the same namespace; :use already :requires it.
It's more usual to use a single :import clause (in fact, a single clause per clause type); for example,
(:import (animals.animal Dog Human Arthropod Insect))
It's purely a matter of style in Clojure, but in ClojureScript it is in fact required by the language.
Most of the top google hits for "calling clojure from java" are outdated and recommend using clojure.lang.RT to compile the source code. Could you help with a clear explanation of how to call Clojure from Java assuming you have already built a jar from the Clojure project and included it in the classpath?
Update: Since this answer was posted, some of the tools available have changed. After the original answer, there is an update including information on how to build the example with current tools.
It isn't quite as simple as compiling to a jar and calling the internal methods. There do seem to be a few tricks to make it all work though. Here's an example of a simple Clojure file that can be compiled to a jar:
(ns com.domain.tiny
(:gen-class
:name com.domain.tiny
:methods [#^{:static true} [binomial [int int] double]]))
(defn binomial
"Calculate the binomial coefficient."
[n k]
(let [a (inc n)]
(loop [b 1
c 1]
(if (> b k)
c
(recur (inc b) (* (/ (- a b) b) c))))))
(defn -binomial
"A Java-callable wrapper around the 'binomial' function."
[n k]
(binomial n k))
(defn -main []
(println (str "(binomial 5 3): " (binomial 5 3)))
(println (str "(binomial 10042 111): " (binomial 10042 111)))
)
If you run it, you should see something like:
(binomial 5 3): 10
(binomial 10042 111): 49068389575068144946633777...
And here's a Java program that calls the -binomial function in the tiny.jar.
import com.domain.tiny;
public class Main {
public static void main(String[] args) {
System.out.println("(binomial 5 3): " + tiny.binomial(5, 3));
System.out.println("(binomial 10042, 111): " + tiny.binomial(10042, 111));
}
}
It's output is:
(binomial 5 3): 10.0
(binomial 10042, 111): 4.9068389575068143E263
The first piece of magic is using the :methods keyword in the gen-class statement. That seems to be required to let you access the Clojure function something like static methods in Java.
The second thing is to create a wrapper function that can be called by Java. Notice that the second version of -binomial has a dash in front of it.
And of course the Clojure jar itself must be on the class path. This example used the Clojure-1.1.0 jar.
Update: This answer has been re-tested using the following tools:
Clojure 1.5.1
Leiningen 2.1.3
JDK 1.7.0 Update 25
The Clojure Part
First create a project and associated directory structure using Leiningen:
C:\projects>lein new com.domain.tiny
Now, change to the project directory.
C:\projects>cd com.domain.tiny
In the project directory, open the project.clj file and edit it such that the contents are as shown below.
(defproject com.domain.tiny "0.1.0-SNAPSHOT"
:description "An example of stand alone Clojure-Java interop"
:url "http://clarkonium.net/2013/06/java-clojure-interop-an-update/"
:license {:name "Eclipse Public License"
:url "http://www.eclipse.org/legal/epl-v10.html"}
:dependencies [[org.clojure/clojure "1.5.1"]]
:aot :all
:main com.domain.tiny)
Now, make sure all of the dependencies (Clojure) are available.
C:\projects\com.domain.tiny>lein deps
You may see a message about downloading the Clojure jar at this point.
Now edit the Clojure file C:\projects\com.domain.tiny\src\com\domain\tiny.clj such that it contains the Clojure program shown in the original answer. (This file was created when Leiningen created the project.)
Much of the magic here is in the namespace declaration. The :gen-class tells the system to create a class named com.domain.tiny with a single static method called binomial, a function taking two integer arguments and returning a double. There are two similarly named functions binomial, a traditional Clojure function, and -binomial and wrapper accessible from Java. Note the hyphen in the function name -binomial. The default prefix is a hyphen, but it can be changed to something else if desired. The -main function just makes a couple of calls to the binomial function to assure that we are getting the correct results. To do that, compile the class and run the program.
C:\projects\com.domain.tiny>lein run
You should see output shown in the original answer.
Now package it up in a jar and put it someplace convenient. Copy the Clojure jar there too.
C:\projects\com.domain.tiny>lein jar
Created C:\projects\com.domain.tiny\target\com.domain.tiny-0.1.0-SNAPSHOT.jar
C:\projects\com.domain.tiny>mkdir \target\lib
C:\projects\com.domain.tiny>copy target\com.domain.tiny-0.1.0-SNAPSHOT.jar target\lib\
1 file(s) copied.
C:\projects\com.domain.tiny>copy "C:<path to clojure jar>\clojure-1.5.1.jar" target\lib\
1 file(s) copied.
The Java Part
Leiningen has a built-in task, lein-javac, that should be able to help with the Java compilation. Unfortunately, it seems to be broken in version 2.1.3. It can't find the installed JDK and it can't find the Maven repository. The paths to both have embedded spaces on my system. I assume that is the problem. Any Java IDE could handle the compilation and packaging too. But for this post, we're going old school and doing it at the command line.
First create the file Main.java with the contents shown in the original answer.
To compile java part
javac -g -cp target\com.domain.tiny-0.1.0-SNAPSHOT.jar -d target\src\com\domain\Main.java
Now create a file with some meta-information to add to the jar we want to build. In Manifest.txt, add the following text
Class-Path: lib\com.domain.tiny-0.1.0-SNAPSHOT.jar lib\clojure-1.5.1.jar
Main-Class: Main
Now package it all up into one big jar file, including our Clojure program and the Clojure jar.
C:\projects\com.domain.tiny\target>jar cfm Interop.jar Manifest.txt Main.class lib\com.domain.tiny-0.1.0-SNAPSHOT.jar lib\clojure-1.5.1.jar
To run the program:
C:\projects\com.domain.tiny\target>java -jar Interop.jar
(binomial 5 3): 10.0
(binomial 10042, 111): 4.9068389575068143E263
The output is essentially identical to that produced by Clojure alone, but the result has been converted to a Java double.
As mentioned, a Java IDE will probably take care of the messy compilation arguments and the packaging.
As of Clojure 1.6.0, there is a new preferred way to load and invoke Clojure functions. This method is now preferred to calling RT directly (and supersedes many of the other answers here). The javadoc is here - the main entry point is clojure.java.api.Clojure.
To lookup and call a Clojure function:
IFn plus = Clojure.var("clojure.core", "+");
plus.invoke(1, 2);
Functions in clojure.core are automatically loaded. Other namespaces can be loaded via require:
IFn require = Clojure.var("clojure.core", "require");
require.invoke(Clojure.read("clojure.set"));
IFns can be passed to higher order functions, e.g. the example below passes plus to read:
IFn map = Clojure.var("clojure.core", "map");
IFn inc = Clojure.var("clojure.core", "inc");
map.invoke(inc, Clojure.read("[1 2 3]"));
Most IFns in Clojure refer to functions. A few, however, refer to non-function data values. To access these, use deref instead of fn:
IFn printLength = Clojure.var("clojure.core", "*print-length*");
IFn deref = Clojure.var("clojure.core", "deref");
deref.invoke(printLength);
Sometimes (if using some other part of the Clojure runtime), you may need to ensure that the Clojure runtime is properly initialized - calling a method on the Clojure class is sufficient for this purpose. If you do not need to call a method on Clojure, then simply causing the class to load is sufficient (in the past there has been a similar recommendation to load the RT class; this is now preferred):
Class.forName("clojure.java.api.Clojure")
EDIT This answer was written in 2010, and worked at that time. See Alex Miller's answer for more modern solution.
What kind of code are calling from Java? If you have class generated with gen-class, then simply call it. If you want to call function from script, then look to following example.
If you want to evaluate code from string, inside Java, then you can use following code:
import clojure.lang.RT;
import clojure.lang.Var;
import clojure.lang.Compiler;
import java.io.StringReader;
public class Foo {
public static void main(String[] args) throws Exception {
// Load the Clojure script -- as a side effect this initializes the runtime.
String str = "(ns user) (defn foo [a b] (str a \" \" b))";
//RT.loadResourceScript("foo.clj");
Compiler.load(new StringReader(str));
// Get a reference to the foo function.
Var foo = RT.var("user", "foo");
// Call it!
Object result = foo.invoke("Hi", "there");
System.out.println(result);
}
}
EDIT: I wrote this answer almost three years ago. In Clojure 1.6 there is a proper API exactly for the purpose of calling Clojure from Java. Please Alex Miller's answer for up to date information.
Original answer from 2011:
As I see it, the simplest way (if you don't generate a class with AOT compilation) is to use clojure.lang.RT to access functions in clojure. With it you can mimic what you would have done in Clojure (no need to compile things in special ways):
;; Example usage of the "bar-fn" function from the "foo.ns" namespace from Clojure
(require 'foo.ns)
(foo.ns/bar-fn 1 2 3)
And in Java:
// Example usage of the "bar-fn" function from the "foo.ns" namespace from Java
import clojure.lang.RT;
import clojure.lang.Symbol;
...
RT.var("clojure.core", "require").invoke(Symbol.intern("foo.ns"));
RT.var("foo.ns", "bar-fn").invoke(1, 2, 3);
It is a bit more verbose in Java, but I hope it's clear that the pieces of code are equivalent.
This should work as long as Clojure and the source files (or compiled files) of your Clojure code is on the classpath.
I agree with clartaq's answer, but I felt that beginners could also use:
step-by-step information on how to actually get this running
information that's current for Clojure 1.3 and recent versions of leiningen.
a Clojure jar that also includes a main function, so it can be run standalone or linked as a library.
So I covered all that in this blog post.
The Clojure code looks like this:
(ns ThingOne.core
(:gen-class
:methods [#^{:static true} [foo [int] void]]))
(defn -foo [i] (println "Hello from Clojure. My input was " i))
(defn -main [] (println "Hello from Clojure -main." ))
The leiningen 1.7.1 project setup looks like this:
(defproject ThingOne "1.0.0-SNAPSHOT"
:description "Hello, Clojure"
:dependencies [[org.clojure/clojure "1.3.0"]]
:aot [ThingOne.core]
:main ThingOne.core)
The Java code looks like this:
import ThingOne.*;
class HelloJava {
public static void main(String[] args) {
System.out.println("Hello from Java!");
core.foo (12345);
}
}
Or you can also get all the code from this project on github.
This works with Clojure 1.5.0:
public class CljTest {
public static Object evalClj(String a) {
return clojure.lang.Compiler.load(new java.io.StringReader(a));
}
public static void main(String[] args) {
new clojure.lang.RT(); // needed since 1.5.0
System.out.println(evalClj("(+ 1 2)"));
}
}
If the use case is to include a JAR built with Clojure in a Java application, I have found having a separate namespace for the interface between the two worlds to be beneficial:
(ns example-app.interop
(:require [example-app.core :as core])
;; This example covers two-way communication: the Clojure library
;; relies on the wrapping Java app for some functionality (through
;; an interface that the Clojure library provides and the Java app
;; implements) and the Java app calls the Clojure library to perform
;; work. The latter case is covered by a class provided by the Clojure lib.
;;
;; This namespace should be AOT compiled.
;; The interface that the java app can implement
(gen-interface
:name com.example.WeatherForecast
:methods [[getTemperature [] Double]])
;; The class that the java app instantiates
(gen-class
:name com.example.HighTemperatureMailer
:state state
:init init
;; Dependency injection - take an instance of the previously defined
;; interface as a constructor argument
:constructors {[com.example.WeatherForecast] []}
:methods [[sendMails [] void]])
(defn -init [weather-forecast]
[[] {:weather-forecast weather-forecast}])
;; The actual work is done in the core namespace
(defn -sendMails
[this]
(core/send-mails (.state this)))
The core namespace can use the injected instance to accomplish its tasks:
(ns example-app.core)
(defn send-mails
[{:keys [weather-forecast]}]
(let [temp (.getTemperature weather-forecast)] ...))
For testing purposes, the interface can be stubbed:
(example-app.core/send-mails
(reify com.example.WeatherForecast (getTemperature [this] ...)))
Other technique that works also with other languages on top of JVM is to declare an interface for functions you want to call and then use 'proxy' function to create instance that implemennts them.
You can also use AOT compilation to create class files representing your clojure code. Read the documentation about compilation, gen-class and friends in the Clojure API docs for the details about how to do this, but in essence you will create a class that calls clojure functions for each method invocation.
Another alternative is to use the new defprotocol and deftype functionality, which will also require AOT compilation but provide better performance. I don't know the details of how to do this yet, but a question on the mailing list would probably do the trick.