解码 base64 数据，无法下载为文件

Question

我正在以 String 格式获取 base64 编码数据。我正在尝试解码 base64 并希望作为文件下载。我已经注释了以下几行代码，这些代码在哪里出错了。

我不确定如何解码数据。

String contentByte=null;
for (SearchHit contenthit : contentSearchHits) {

    Map<String, Object> sourceAsMap = contenthit.getSourceAsMap();
    fileName=sourceAsMap.get("Name").toString();
    System.out.println("FileName ::::"+fileName);
    contentByte =  sourceAsMap.get("resume").toString();

}
System.out.println("Bytes --->"+contentByte);

 File file = File.createTempFile("Testing",".pdf", new File("D:/") );
 file.deleteOnExit();
 BufferedWriter out = new BufferedWriter(new FileWriter(file));
  out.write(Base64.getDecoder().decode(contentByte)); //getting error on this line

请找出下面的编译错误。

The method write(int) in the type BufferedWriter is not applicable for the arguments (byte[])

我使用的是 Java 8 版本

Answer 1

Writers 用于写入字符，而不是字节。要写入字节，您应该使用OutputStream 的一些风格。见Writer or OutputStream?

但是，如果您只想将字节数组写入文件，Files 类提供了一个 Files.write 方法来执行此操作：

byte[] bytes = Base64.getDecoder().decode(contentByte);
Files.write(file.toPath(), bytes);

Answer 2

import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.util.Base64;

public class Example {

public static void main(String[] args) {

    String contentByte="Simple text send from server";
    byte[] bytes = 
    Base64.getEncoder().encode(contentByte.getBytes(StandardCharsets.UTF_8));
    //Data received by you at server end(base64 encoded data as string)
    contentByte = new String(bytes);

    System.out.println(new String(bytes));

    BufferedWriter out = null;
    System.out.println("Bytes --->"+contentByte);
    try {
        File file = File.createTempFile("Testing",".pdf", new File("/tmp/") );
       // file.deleteOnExit(); // this line will remove file and your data will not going to save to file. So remove this line.
        out = new BufferedWriter(new FileWriter(file));
        byte[] decodedImg = 
      Base64.getDecoder().decode(contentByte.getBytes(StandardCharsets.UTF_8));
        out.write(new String(decodedImg)); //getting error on this line

    }catch (Exception e)
    {
        e.printStackTrace();
    }finally {
        if(out!=null)
        {
            try {
                out.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
   }
 }

以上解决方案可能对您有所帮助。