archive

Mon, 01 Jan 0001 00:00:00 +0000

example #

1. 编写NativeLibrary.h #

#include <string>

namespace NativeLibrary {
 class NativeClass {
 public:
 const std::string& get_property() { return property; }
 void set_property(const std::string& property) { this->property = property; }
 std::string property;
 };
}

2. 编写NativeLibrary.java #

import org.bytedeco.javacpp.*;
import org.bytedeco.javacpp.annotation.*;

@Platform(include="NativeLibrary.h")
@Namespace("NativeLibrary")
public class NativeLibrary {
 public static class NativeClass extends Pointer {
 static { Loader.load(); }
 public NativeClass() { allocate(); }
 private native void allocate();

 // to call the getter and setter functions 
 public native @StdString String get_property(); public native void set_property(String property);

 // to access the member variable directly
 public native @StdString String property(); public native void property(String property);
 }

 public static void main(String[] args) {
 // Pointer objects allocated in Java get deallocated once they become unreachable,
 // but C++ destructors can still be called in a timely fashion with Pointer.deallocate()
 NativeClass l = new NativeClass();
 l.set_property("Hello World!");
 System.out.println(l.property());
 }
}

3. 执行 #

$ java -jar javacpp-1.5.9.jar NativeLibrary.java -exec

4. 记录 #

Mon, 01 Jan 0001 00:00:00 +0000

example #

1. 导入需要的依赖包 #

<!-- https://mvnrepository.com/artifact/net.java.dev.jna/jna -->
<dependency>
 <groupId>net.java.dev.jna</groupId>
 <artifactId>jna</artifactId>
 <version>5.13.0</version>
</dependency>

2. 编写代码 #

The following program loads the local C standard library implementation and uses it to call the printf function.
Note: The following code is portable and works the same on Windows and POSIX (Linux / Unix / macOS) platforms.

Mon, 01 Jan 0001 00:00:00 +0000

example #

1. 写一段包含C方法实现的java代码 #

// Save as HelloJNI.java
public class HelloJNI{
 static {
 // Load native library hello.dll (Windows) or libhello.so (Unixes) at runtime
 // This library contains a native method called sayHello()
 System.loadLibrary("hello");
 }
 // Declare an instance native method sayHello() which receives no parameter and returns void
 private native void sayHello();
 public static void main(String[] args){
 // Create an instance and invoke the native method
 new HelloJNI().sayHello();
 }
}

The static initializer invokes System.loadLibrary() to load the native library “hello” (which contains a native method called sayHello()) during the class loading. It will be mapped to “hello.dll” in Windows; or “libhello.so” in Unixes/Mac OS X. This library shall be included in Java’s library path (kept in Java system variable java.library.path). You could include the library into Java’s library path via VM argument -Djava.library.path=/path/to/lib. The program will throw a UnsatisfiedLinkError if the library cannot be found in runtime.