"基本参考[链接]，java 下载直接安装，注意文件名和类名需要一致的问题； redis 下载以后按[链接]linux 下安装，方式编译运行 ok； Java 使用 redis 按[链接]下载.jar，保存在本地某个路径，然后配 classpath 按[链接]的第一种方法： export CLASSP ...."

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Java Redis JNI

基本参考菜鸟教程，java 下载直接安装，注意文件名和类名需要一致的问题；

redis 下载以后按菜鸟教程linux 下安装，方式编译运行 ok；

Java 使用 redis 按菜鸟教程下载.jar，保存在本地某个路径，然后配 classpath 按这里的第一种方法：

export CLASSPATH=$CLASSPATH:/path/to/file/java-servlet-api.jar
source ～/.bash_profile         //网站上少了～/

代码来自菜鸟教程：

import redis.clients.jedis.Jedis;
public class helloworld{
  public static void main(String[] args){
    System.out.println("Hello World");
    Jedis jedis = new Jedis("localhost");
    System.out.println("success");
    System.out.println("running:"+jedis.ping());}
}

效果：

javaTest song$ java helloworld
Hello World
success
running: PONG

jni 编译路径找不到，mac os 在这里：

/Library/Java/JavaVirtualMachines/jdk-9.0.4.jdk/Contents/Home/include/jni.h
/Library/Java/JavaVirtualMachines/jdk-9.0.4.jdk/Contents/Home/include/darwin/jni_md.h

------------18.03.12 Java 读取图像并保存 ----------

多方参考，这里的代码可以读取，应该有什么依赖环境没装上，所以不能显示，想把读到的图片另存在本地，保存总是报错，后来添加头文件可以了。

import javax.imageio.*;//for ImageIO.read
import java.util.Arrays;
import java.awt.image.BufferedImage;
import java.awt.*;//for JFrame and JLabel etc
import javax.swing.*;//for JFrame and JLabel etc
import java.net.*;//for URL
import java.io.*;//for catch (IOException e),File,InputStream, BufferedInputStream,and FileInputStream ect
public class HelloJava{
   public static void main (String[] args){
    try {
        // Read from a file
        File sourceimage = new File("test.jpg");  //source.gif 图片要与 HelloJava.java 同在一目录下
        BufferedImage image = ImageIO.read(sourceimage);
        File f = new File("test1.jpg");
        ImageIO.write(image, "jpg", f);
    </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> Read from a URL(topit.me网站上随便找了一张图）</span>
    URL url = <span style="color: rgba(0, 0, 255, 1)">new</span> URL(<span style="color: rgba(128, 0, 0, 1)">"</span><span style="color: rgba(128, 0, 0, 1)">http://www.topit.cc/uploads/20180303/17/1520068648-XwNkvKgBVP.jpg</span><span style="color: rgba(128, 0, 0, 1)">"</span><span style="color: rgba(0, 0, 0, 1)">);
    image </span>=<span style="color: rgba(0, 0, 0, 1)"> ImageIO.read(url);
    f </span>= <span style="color: rgba(0, 0, 255, 1)">new</span> File(<span style="color: rgba(128, 0, 0, 1)">"</span><span style="color: rgba(128, 0, 0, 1)">topit.jpg</span><span style="color: rgba(128, 0, 0, 1)">"</span><span style="color: rgba(0, 0, 0, 1)">);
    ImageIO.write(image, </span><span style="color: rgba(128, 0, 0, 1)">"</span><span style="color: rgba(128, 0, 0, 1)">jpg</span><span style="color: rgba(128, 0, 0, 1)">"</span><span style="color: rgba(0, 0, 0, 1)">, f);
} </span><span style="color: rgba(0, 0, 255, 1)">catch</span><span style="color: rgba(0, 0, 0, 1)"> (IOException e) {
}

}
}

RGB 转灰度：

import javax.imageio.*;//for ImageIO.read
import java.util.Arrays;
import java.awt.image.BufferedImage;
import java.awt.*;//for JFrame and JLabel etc
import javax.swing.*;//for JFrame and JLabel etc
import java.net.*;//for URL
import java.io.*;//for catch (IOException e),File,InputStream, BufferedInputStream,and FileInputStream ect
public class readRGB2Grey{
   public static void main (String[] args){
    try {
        // Read from a file
        File sourceimage = new File("topit_cut.jpg");  //source.gif 图片要与 HelloJava.java 同在一目录下
        BufferedImage image = ImageIO.read(sourceimage);
    </span><span style="color: rgba(0, 0, 255, 1)">int</span> width=<span style="color: rgba(0, 0, 0, 1)">image.getWidth();  
</span><span style="color: rgba(0, 0, 255, 1)">int</span> height=<span style="color: rgba(0, 0, 0, 1)">image.getHeight();  
</span><span style="color: rgba(0, 0, 255, 1)">int</span> imaRGB[][]=<span style="color: rgba(0, 0, 255, 1)">new</span> <span style="color: rgba(0, 0, 255, 1)">int</span>[width][height];<span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">存放RGB信息数组，重点  </span>
    <span style="color: rgba(0, 0, 255, 1)">int</span> grey[][]=<span style="color: rgba(0, 0, 255, 1)">new</span> <span style="color: rgba(0, 0, 255, 1)">int</span>[width][height];<span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">存放RGB信息数组，重点  
</span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">从bufIma读取RGB到数组中  </span>
<span style="color: rgba(0, 0, 255, 1)">int</span> minx =<span style="color: rgba(0, 0, 0, 1)"> image.getMinX();
    </span><span style="color: rgba(0, 0, 255, 1)">int</span> miny =<span style="color: rgba(0, 0, 0, 1)"> image.getMinY();
    </span><span style="color: rgba(0, 0, 255, 1)">int</span>[] rgb = <span style="color: rgba(0, 0, 255, 1)">new</span> <span style="color: rgba(0, 0, 255, 1)">int</span>[<span style="color: rgba(128, 0, 128, 1)">3</span><span style="color: rgba(0, 0, 0, 1)">];
    </span><span style="color: rgba(0, 0, 255, 1)">for</span> (<span style="color: rgba(0, 0, 255, 1)">int</span> i = minx; i &lt; width; i++<span style="color: rgba(0, 0, 0, 1)">) {
        </span><span style="color: rgba(0, 0, 255, 1)">for</span> (<span style="color: rgba(0, 0, 255, 1)">int</span> j = miny; j &lt; height; j++<span style="color: rgba(0, 0, 0, 1)">) {
            </span><span style="color: rgba(0, 0, 255, 1)">int</span> pixel = image.getRGB(i, j);<span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">获得像素值</span>
            rgb[<span style="color: rgba(128, 0, 128, 1)">0</span>] = (pixel &amp; <span style="color: rgba(128, 0, 128, 1)">0xff0000</span>) &gt;&gt; <span style="color: rgba(128, 0, 128, 1)">16</span><span style="color: rgba(0, 0, 0, 1)">;
            rgb[</span><span style="color: rgba(128, 0, 128, 1)">1</span>] = (pixel &amp; <span style="color: rgba(128, 0, 128, 1)">0xff00</span>) &gt;&gt; <span style="color: rgba(128, 0, 128, 1)">8</span><span style="color: rgba(0, 0, 0, 1)">;
            rgb[</span><span style="color: rgba(128, 0, 128, 1)">2</span>] = (pixel &amp; <span style="color: rgba(128, 0, 128, 1)">0xff</span><span style="color: rgba(0, 0, 0, 1)">);
            </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">此处为将像素值转换为灰度值的方法，存在误差，算法不唯一</span>
            grey[i][j] = (rgb[<span style="color: rgba(128, 0, 128, 1)">0</span>]*<span style="color: rgba(128, 0, 128, 1)">150</span>+rgb[<span style="color: rgba(128, 0, 128, 1)">1</span>]*<span style="color: rgba(128, 0, 128, 1)">59</span>+rgb[<span style="color: rgba(128, 0, 128, 1)">2</span>]*<span style="color: rgba(128, 0, 128, 1)">11</span>+<span style="color: rgba(128, 0, 128, 1)">150</span>)/<span style="color: rgba(128, 0, 128, 1)">150</span><span style="color: rgba(0, 0, 0, 1)">;  
        }
    }
     
    </span><span style="color: rgba(0, 0, 255, 1)">for</span>(<span style="color: rgba(0, 0, 255, 1)">int</span> i=<span style="color: rgba(128, 0, 128, 1)">0</span>;i&lt;width;i++<span style="color: rgba(0, 0, 0, 1)">){ 
      System.</span><span style="color: rgba(0, 0, 255, 1)">out</span>.print(<span style="color: rgba(128, 0, 0, 1)">"</span><span style="color: rgba(128, 0, 0, 1)">\n</span><span style="color: rgba(128, 0, 0, 1)">"</span><span style="color: rgba(0, 0, 0, 1)">); 
      </span><span style="color: rgba(0, 0, 255, 1)">for</span>(<span style="color: rgba(0, 0, 255, 1)">int</span> j=<span style="color: rgba(128, 0, 128, 1)">0</span>;j&lt;height;j++<span style="color: rgba(0, 0, 0, 1)">)  
         System.</span><span style="color: rgba(0, 0, 255, 1)">out</span>.print(<span style="color: rgba(128, 0, 0, 1)">"</span> <span style="color: rgba(128, 0, 0, 1)">"</span>+<span style="color: rgba(0, 0, 0, 1)">grey[i][j]);  
    }         
    System.</span><span style="color: rgba(0, 0, 255, 1)">out</span>.print(<span style="color: rgba(128, 0, 0, 1)">"</span><span style="color: rgba(128, 0, 0, 1)">image size: </span><span style="color: rgba(128, 0, 0, 1)">"</span>+width+<span style="color: rgba(128, 0, 0, 1)">"</span><span style="color: rgba(128, 0, 0, 1)"> , </span><span style="color: rgba(128, 0, 0, 1)">"</span>+<span style="color: rgba(0, 0, 0, 1)">height);  
    System.</span><span style="color: rgba(0, 0, 255, 1)">out</span>.print(<span style="color: rgba(128, 0, 0, 1)">"</span><span style="color: rgba(128, 0, 0, 1)">minx: </span><span style="color: rgba(128, 0, 0, 1)">"</span>+width+<span style="color: rgba(128, 0, 0, 1)">"</span><span style="color: rgba(128, 0, 0, 1)"> , miny: </span><span style="color: rgba(128, 0, 0, 1)">"</span>+<span style="color: rgba(0, 0, 0, 1)">height);  
} </span><span style="color: rgba(0, 0, 255, 1)">catch</span><span style="color: rgba(0, 0, 0, 1)"> (IOException e) {
}

}
}

------18.03.14 jni---------------------

java 用 JNI 调 c++ 程序包搞了两天半，基本是参考前人程序，步骤：

先编译通过 c++ 程序，测试没问题以后打包成动态链接库，拷贝 c.hpp 到 java 目录；

在 java 工程目录下新建目录：com/test/，进入目录写 java ：helloword.java

javac helloword.java，如果没问题会生成 hello.class

回到主目录 javah com.test.helloword，如果没问题会生成 com_test_nativehelloword.h

参考.h 里的定义写 jni_nativehelloword.cpp，在这里 include<c.hpp> 调 c++ 生成的动态链接库。

注意事项：

如果要返回一个 jobject(ArrayList), jni 里是返回 jobject, return NULL, java 里判断 ArrayList 是否为空用 (arraylist!=null&&.size()>0), 注意大小写。

-------18.03.15 jni-------------------

c++ 代码种新加了一个函数，java jni 全更新过一遍，报错：

Undefined symbols for architecture x86_64:
  "_queryDB", referenced from:
      method_table in jni_SearchImage-a0aaca.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

整个检查了一圈，各种怀疑，后来发现是 jni 里的函数名写错了。

Java Redis JNI

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Java Redis JNI