Runtime.exec()调用imageMagick实现图片缩放

最新推荐文章于 2023-01-15 16:41:05 发布

guo_yang

最新推荐文章于 2023-01-15 16:41:05 发布

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CC 4.0 BY-SA版权

本文链接：https://blog.youkuaiyun.com/guo_yang/article/details/82186128

本文介绍了解决Java中Runtime.getRuntime().exec()方法导致程序阻塞的问题。通过创建独立线程处理stdout和stderr流，确保了程序流畅运行，并提供了一个图片缩放工具类的具体实现案例。

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牛牛发现问题的原因，Process process=Runtime.getRuntime().exec("");中产生停滞（阻塞，blocking）。

这个是因为Runtime.getRuntime().exec()要自己去处理stdout和stderr的。
所以如果你想让程序正常运行的话，请务必将上述用别的线程流取走。

public class PictureZoomUtils {
private static Log logger = LogFactory.getLog(PictureZoomUtils.class);
/**
* image magick convert.exe的绝对路径
*/
private String convertExe;
public void zoom(File input, File output, int width, int height) throws Exception {
StringBuilder command = new StringBuilder();
command.append(convertExe).append(" ").append(input.getAbsolutePath()).append(" -resize ").append(width)
.append("x").append(height)// 改变尺寸 -resize 120x120
.append(" -colors").append(" 100") // 颜色数：设定图片采用的颜色数，如果是生成png或gif图片应指定这个参数
.append(" +profile \"*\" ") // 图片中不存储附加信息，必须使用，否则生成图片过大
.append(output.getAbsolutePath());
try{
Process process = Runtime.getRuntime().exec(command.toString());
// any error message?
StreamGobbler errorGobbler = new StreamGobbler(process.getErrorStream(), "ERROR");
// any output?
StreamGobbler outputGobbler = new StreamGobbler(process.getInputStream(), "OUTPUT");
errorGobbler.start();
outputGobbler.start();
process.waitFor(); // 永远要先从标准错误流中读取，然后再读取标准输出流，最后在执行waitFor
}catch(Throwable t){
logger.error(t);
}
}
public void setConvertExe(String convertExe) {
this.convertExe = convertExe;
}
public String getConvertExe() {
return convertExe;
}
}
class StreamGobbler extends Thread {
private static Log logger = LogFactory.getLog(StreamGobbler.class);
private InputStream is;
private String type; // 输出流的类型ERROR或OUTPUT
public StreamGobbler(InputStream is, String type) {
this.is = is;
this.type = type;
}
public void run() {
try {
InputStreamReader isr = new InputStreamReader(is);
BufferedReader br = new BufferedReader(isr);
String line = null;
while ((line = br.readLine()) != null) {
System.out.println(type + ">" + line);
System.out.flush();
}
} catch (IOException ioe) {
logger.error(ioe);
}
}
}

public class PictureZoomUtils {   private static Log logger = LogFactory.getLog(PictureZoomUtils.class);      /**    * image magick convert.exe的绝对路径    */   private String convertExe;     public void zoom(File input, File output, int width, int height) throws Exception {    StringBuilder command = new StringBuilder();    command.append(convertExe).append(" ").append(input.getAbsolutePath()).append(" -resize ").append(width)      .append("x").append(height)// 改变尺寸 -resize 120x120      .append(" -colors").append(" 100") // 颜色数：设定图片采用的颜色数，如果是生成png或gif图片应指定这个参数      .append(" +profile \"*\" ") // 图片中不存储附加信息，必须使用，否则生成图片过大      .append(output.getAbsolutePath());      try{     Process process = Runtime.getRuntime().exec(command.toString());       // any error message?     StreamGobbler errorGobbler = new StreamGobbler(process.getErrorStream(), "ERROR");     // any output?     StreamGobbler outputGobbler = new StreamGobbler(process.getInputStream(), "OUTPUT");       errorGobbler.start();     outputGobbler.start();       process.waitFor(); // 永远要先从标准错误流中读取，然后再读取标准输出流， 最后在执行waitFor    }catch(Throwable t){     logger.error(t);    }       }     public void setConvertExe(String convertExe) {    this.convertExe = convertExe;   }     public String getConvertExe() {    return convertExe;   }    }    class StreamGobbler extends Thread {   private static Log logger = LogFactory.getLog(StreamGobbler.class);      private InputStream is;   private String type; // 输出流的类型ERROR或OUTPUT     public StreamGobbler(InputStream is, String type) {    this.is = is;    this.type = type;   }     public void run() {    try {     InputStreamReader isr = new InputStreamReader(is);     BufferedReader br = new BufferedReader(isr);     String line = null;     while ((line = br.readLine()) != null) {      System.out.println(type + ">" + line);      System.out.flush();     }    } catch (IOException ioe) {     logger.error(ioe);    }   }  }