在ExecuteScript NiFi中写入新流文件时出现的问题

Question

我正在尝试使用ExecuteScript处理器执行一段java代码来过滤csv文件并输出一个新的csv文件。

将出现错误:未指定调拨关系。我怎么才能修复它呢？

我的代码：

FlowFile flowFile = session.get();
    if (flowFile == null) {
      return;
    }
FlowFile newflowFile = session.create();

try {
Reader reader = Files.newBufferedReader(Paths.get(flowFile), StandardCharsets.UTF-8);
Writer writer = Files.newBufferedWriter(Paths.get(newflowFile), StandardCharsets.UTF-8, StandardOpenOption.CREATE);
CSVPrinter printer = CSVFormat.DEFAULT.print(writer);

...
//using printer write a new content

session.transfer(newflowFile, REL_SUCCESS);

} catch (Exception e) {

session.transfer(flowFile, REL_FAILURE);
}

Answer 1

我建议你使用ExecuteGroovyScript而不是ExecuteScript -它有更多的功能，而且它只需在处理器初始化时编译一次。所以，它的速度要快一点。

如果您计划从同一个流文件中读取数据或将数据写入同一个流文件，这里是该脚本的基础。

def ff=session.get()
if(!ff)return

ff.write{InputStream rawIn, OutputStream rawOut->
    //rawIn - current flowfile content
    //rawOut - stream for a new flowfile content
    rawIn.withReader("UTF-8"){reader->
        rawOut.withWriter("UTF-8"){writer->
            CSVPrinter printer = CSVFormat.DEFAULT.print(writer)
            ...
        }
    }
}

REL_SUCCESS << ff  //the same as session.transfer