FlatBuffers - 布尔值

概述

bool 数据类型是 FlatBuffers 的基本构建块之一。它在使用的语言中翻译为布尔值，例如Java、Python 等。

继续我们从FlatBuffers - 字符串章节的剧院示例，以下是我们需要使用的语法，以指示 FlatBuffers 我们将创建bool值：

theater.fbs

namespace com.tutorialspoint.theater;

table Theater {
   drive_in:bool;
}
root_type Theater;

现在我们的表格包含一个bool属性。默认值为false。

从 FBS 文件创建 Java 类

要使用 FlatBuffers，我们现在必须使用flatc二进制文件从这个“.fbs”文件创建所需的类。让我们看看如何操作：

flatc  --java theater.fbs

这将在当前目录的com > tutorialspoint > theater文件夹中创建一个Theater.java类。我们在应用程序中使用此类，类似于FlatBuffers - Schema章节中所做的那样。

使用从 fbs 文件创建的 Java 类

TheaterWriter.java

package com.tutorialspoint.theater;

import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

import com.google.flatbuffers.FlatBufferBuilder;

public class TheaterWriter {
   public static void main(String[] args) throws FileNotFoundException, IOException {
      // create a flat buffer builder
      // it will be used to create Theater FlatBuffer
      FlatBufferBuilder builder = new FlatBufferBuilder(1024);

      boolean driveIn = true; 

      // create theater FlatBuffers using startTheater() method
      Theater.startTheater(builder);
      // add details to the Theater FlatBuffer
      Theater.addDriveIn(builder, driveIn);

      // mark end of data being entered in Greet FlatBuffer
      int theater = Theater.endTheater(builder);

      // finish the builder
      builder.finish(theater);

      // get the bytes to be stored
      byte[] data = builder.sizedByteArray();

      String filename = "theater_flatbuffers_output";
      System.out.println("Saving theater to file: " + filename);
      // write the builder content to the file named theater_flatbuffers_output
      try(FileOutputStream output = new FileOutputStream(filename)){
         output.write(data);
      }
      System.out.println("Saved theater with following data to disk: \n" + theater);
   }
}	

接下来，我们将有一个读取器来读取剧院信息：

TheaterReader.java

package com.tutorialspoint.theater;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.nio.ByteBuffer;

public class TheaterReader {
   public static void main(String[] args) throws FileNotFoundException, IOException {

      String filename = "theater_flatbuffers_output";
      System.out.println("Reading from file " + filename);
      try(FileInputStream input = new FileInputStream(filename)) {
         // get the serialized data
         byte[] data = input.readAllBytes();
         ByteBuffer buf = ByteBuffer.wrap(data);
         // read the root object in serialized data
         Theater theater = Theater.getRootAsTheater(buf);
         // print theater values 
         System.out.println("Drive In: " + theater.driveIn());
      }
   }
}

编译项目

现在我们已经设置了读取器和写入器，让我们编译项目。

mvn clean install

序列化 Java 对象

现在，编译后，让我们先执行写入器：

java -cp .\target\flatbuffers-tutorial-1.0.jar com.tutorialspoint.theater.TheaterWriter

Saving theater to file: theater_flatbuffers_output
Saved theater with following data to disk:
8

反序列化已序列化的对象

现在，让我们执行读取器以从同一文件读取：

java -cp .\target\flatbuffers-tutorial-1.0.jar com.tutorialspoint.theater.TheaterReader

Reading from file theater_flatbuffers_output
Drive In: true

因此，正如我们所看到的，我们能够通过将二进制数据反序列化为剧院对象来读取已序列化的字符串。让我们在下一章FlatBuffers - 枚举中查看数字。