String與Blob互轉(zhuǎn)和file文件與Blob互轉(zhuǎn)方式

更新時間：2023年05月31日 09:47:02 作者：膩&愛

這篇文章主要介紹了String與Blob互轉(zhuǎn)和file文件與Blob互轉(zhuǎn)方式，具有很好的參考價值，希望對大家有所幫助。如有錯誤或未考慮完全的地方，望不吝賜教

Blob對字符串類型操作

String轉(zhuǎn)換Blob

可以通過SerialBlob創(chuàng)建Blob對象，SerialBlob下有兩個構(gòu)造函數(shù)，如需創(chuàng)建Blob對象，可以使用 byte[] 類型,先把String轉(zhuǎn)成byte[]再調(diào)用構(gòu)造函數(shù)。

創(chuàng)建SerialBlob對象

String 轉(zhuǎn)換為byte[]

/**
 * String 轉(zhuǎn) byte[]
 * @param str 請求進入字符串
 * @return 返回byte[] 數(shù)組
 * @throws Exception 拋出錯誤
 */
public byte[] readStream(String str) throws Exception {
    InputStream inStream=new ByteArrayInputStream(str.getBytes(StandardCharsets.UTF_8));
    ByteArrayOutputStream outStream = new ByteArrayOutputStream();
    byte[] buffer = new byte[1024];
    int len = 0;
    while ((len = inStream.read(buffer)) != -1) {
        outStream.write(buffer, 0, len);
    }
    outStream.close();
    inStream.close();
    return outStream.toByteArray();
}

byte[] 轉(zhuǎn)為 SerialBlob

Blob blob=new SerialBlob(readStream(str))

Blob轉(zhuǎn)換Sting

同理，Blob類型轉(zhuǎn)換為String，就是反過來，先轉(zhuǎn)換成byte[],再轉(zhuǎn)換成String。

private String blobToString(Blob blob) throws Exception {
     InputStream inStream=blob.getBinaryStream();
     StringBuffer stringBuffer=new StringBuffer();
     try {
         byte[] buffer = new byte[1024];
         int len = 0;
         while ((len = inStream.read(buffer)) != -1) {
             String str=new String(buffer, 0, len);
             stringBuffer.append(str);
         }
     }catch (Exception e){
         throw e;
     }finally {
         if(inStream!=null){
             inStream.close();
         }
         if(stringBuffer.length()>0){
             return stringBuffer.toString();
         }else{
             return null;
         }
     }
 }

File轉(zhuǎn)Blob

可以把File文件先轉(zhuǎn)換成byte[]，再通過SerialBlob對象創(chuàng)建

File轉(zhuǎn)為byte[]

這個方法試試示例，可以去網(wǎng)上找一下File轉(zhuǎn)換byte[]流的方法

//這個方法只是示例，不推薦這樣使用
public static byte[] getFileByte(File file) throws Exception {
	byte[] data = null;
	InputStream in = new FileInputStream(file);
	data = new byte[in.available()];
	in.read(data);
	in.close();
	return data;
}

byte[] 轉(zhuǎn)為 SerialBlob

Blob blob=new SerialBlob(readStream(str))

Blob轉(zhuǎn)File

可以通過Blob轉(zhuǎn)成InputStream，再通過讀取的方式轉(zhuǎn)成File

Blob轉(zhuǎn)InputStream

InputStream in = blob.getBinaryStream()

InputStream轉(zhuǎn)File

public void blobToFile(Blob blob,File file) throws Exception {
	InputStream inStream=null;
	OutputStream outStream=null;
   	try {
		outStream = new FileOutputStream(file);
		int bytesRead = 0;
		byte[] buffer = new byte[2048];
		while ((bytesRead = inStream.read(buffer, 0, 2048)) != -1) {
			outStream.write(buffer, 0, bytesRead);
		}
	}catch (Exception e){
   		throw new Exception(e);
	}finally {
   		if(outStream!=null){
			outStream.close();
		}
		if(inStream!=null){
			inStream.close();
		}
	}
}