Java
javaTutorial
How to implement JNI and local method invocation of Java underlying technology
How to implement JNI and local method invocation of Java underlying technology
Nov 08, 2023 pm 12:26 PM
How to implement JNI and local method invocation of Java's underlying technology
Java is a cross-platform programming language, but sometimes we need to communicate with the underlying C or C code to interact. In Java, we can access local methods through JNI (Java Native Interface) to communicate with the underlying code. This article will introduce how to use JNI to implement Java and native method calls, and provide some specific code examples.
First, we need to prepare a Java class, which will be used to declare the local methods we need to call. For example, we create a class named JNIExample, which declares a local method add, which is used to add two integers and return the result:
public class JNIExample {
static {
System.loadLibrary("JNIExample");
}
public native int add(int a, int b);
}In the above code, we use the static code block to load the native library JNIExample. This native library is a dynamic link library compiled and generated by the C/C code we will use to implement the native method.
Next, we need to write a C/C source file to implement the add method. We name this file JNIExample.cpp. The following is the sample code in JNIExample.cpp:
#include <jni.h>
JNIEXPORT jint JNICALL Java_JNIExample_add(JNIEnv *env, jobject obj, jint a, jint b) {
return a + b;
}In the above code, we implement the add method, and complete the integer addition operation by implementing this method in C/C. The signature of this method must be consistent with the method declared in Java and needs to be modified using the JNIEXPORT and JNICALL macros.
Next, we need to use Java's JNI tool to compile the C/C source files into a platform-related dynamic link library. Use the following command in the command line to compile:
gcc -shared -fpic -I"${JAVA_HOME}/include" -I"${JAVA_HOME}/include/${TARGET}" -o libJNIExample.so JNIExample.cppIn the above command, we use the gcc compiler to compile JNIExample.cpp into the libJNIExample.so dynamic link library. Note that replace ${JAVA_HOME} with the Java installation directory and ${TARGET} with the directory of the target operating system.
After compilation is completed, we will get a dynamic link library named libJNIExample.so. Place this library file in the same directory as your Java class, or specify a path that contains the library.
Finally, we can call the add method of the JNIExample class in the Java program to interact with local methods. The following is a sample code using the JNIExample class:
public class Main {
public static void main(String[] args) {
JNIExample jniExample = new JNIExample();
int result = jniExample.add(10, 20);
System.out.println("Result: " + result);
}
}In the above code, we create a JNIExample object and call its add method. This method will call the add method we implemented previously in C/C and return the result. Finally, we print the results.
Through the above steps, we can use JNI to implement Java and local method calls. Through JNI, we can interact with the underlying C/C code to achieve more flexible and efficient application development.
The above is the detailed content of How to implement JNI and local method invocation of Java underlying technology. For more information, please follow other related articles on the PHP Chinese website!
Hot AI Tools
Undress AI Tool
Undress images for free
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
Clothoff.io
AI clothes remover
Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!
Hot Article
Hot Tools
Notepad++7.3.1
Easy-to-use and free code editor
SublimeText3 Chinese version
Chinese version, very easy to use
Zend Studio 13.0.1
Powerful PHP integrated development environment
Dreamweaver CS6
Visual web development tools
SublimeText3 Mac version
God-level code editing software (SublimeText3)
How to use Python to call Baidu Map API to implement geographical location query function?
Jul 31, 2023 pm 03:01 PM
How to use Python to call Baidu Map API to implement geographical location query function? With the development of the Internet, the acquisition and utilization of geographical location information is becoming more and more important. Baidu Maps is a very common and practical map application that provides a wealth of geographical location query services. This article will introduce how to use Python to call Baidu Map API to implement the geographical location query function, and attach a code example. Apply for a Baidu Map developer account and application First, you need to have a Baidu Map developer account and create an application. Log in
PHP camera calling skills: How to implement multi-camera switching
Aug 04, 2023 pm 07:07 PM
PHP camera calling skills: How to switch between multiple cameras. Camera applications have become an important part of many web applications, such as video conferencing, real-time monitoring, etc. In PHP, we can use various technologies to call and operate the camera. This article will focus on how to implement multi-camera switching and provide some sample code to help readers better understand. Basics of camera calling In PHP, we can call the camera by calling the JavaScript API. Specifically, we
How to solve external resource access and calls in PHP development
Oct 08, 2023 am 11:01 AM
How to solve the problem of accessing and calling external resources in PHP development requires specific code examples. In PHP development, we often encounter situations where we need to access and call external resources, such as API interfaces, third-party libraries or other server resources. When dealing with these external resources, we need to consider how to access and call safely while ensuring performance and reliability. This article describes several common solutions and provides corresponding code examples. 1. Use the curl library to call external resources. Curl is a very powerful open source library.
How matlab calls m files-matlab method of calling m files
Mar 04, 2024 pm 01:49 PM
Many friends still don’t know how to call m files in matlab, so the editor below explains how to call m files in matlab. If you are in need, please take a look. I believe it will be helpful to everyone. 1. First open the matlab software and click "Open" in the main interface, as shown in the figure below. 2. Then select an m file that needs to be opened and select Open, as shown in the figure below. 3. Then look at the file name and number of variables of the m file in the editor, as shown in the figure below. 4. You can enter the m file name followed by the variable value in brackets on the command line to call it, as shown in the figure below. 5. Finally, the m file can be successfully called, as shown in the figure below. The above is the complete description of how to call m files in matlab brought to you by the editor.
How to call Baidu Map API through Python programming to implement map display function?
Aug 02, 2023 pm 08:27 PM
How to call Baidu Map API through Python programming to implement map display function? With the rapid development of the Internet, map applications have become an indispensable part of our lives. As one of the largest map applications in China, Baidu Maps provides us with a wealth of services and API interfaces, which can easily realize the map display function. This article will introduce how to call Baidu Map API through Python programming to realize the map display function, and give corresponding code examples. First, we need to register a
Source code exploration: How are objects called in Python?
May 11, 2023 am 11:46 AM
Wedge We know that objects are created in two main ways, one is through Python/CAPI, and the other is by calling a type object. For instance objects of built-in types, both methods are supported. For example, lists can be created through [] or list(). The former is Python/CAPI and the latter is a calling type object. But for instance objects of custom classes, we can only create them by calling type objects. If an object can be called, then the object is callable, otherwise it is not callable. Determining whether an object is callable depends on whether a method is defined in its corresponding type object. like
How to call WebService using Java
Dec 29, 2023 pm 02:32 PM
The method steps of using Java to call WebService require specific code examples. Web service is a Web-based application program interface that provides various functions through the network. In Java development, we often need to use Web services to interact with other systems. This article will introduce how to use Java to call WebService and provide specific code examples. 1. Understand WebService WebService is a standardized communication protocol using XML format
How to call the camera for license plate recognition through PHP
Aug 02, 2023 pm 01:57 PM
How to call a camera for license plate recognition through PHP Introduction: With the continuous development of technology, license plate recognition technology plays an important role in traffic management, security monitoring and other fields. This article will introduce how to use PHP to write a program to implement the license plate recognition function by calling the camera. 1. Overview License plate recognition technology mainly involves image processing and machine learning algorithms. Traditional license plate recognition solutions are developed using programming languages ??such as C++ or Python. However, since PHP is a scripting language widely used in Web development, developers
