前端要预览服务器PDF 可直接将要blob流返回给前端 即可用浏览器自带pdf预览功能打开，现有两种方式
方式1 返回blob流给前端 代码如下
@PostMapping(value = "/preview")
@ResponseBody
public void showPdf(HttpServletResponse response) {
try {
File file = new File("filePath");
OutputStream out = null;
try (BufferedInputStream br = new BufferedInputStream(new FileInputStream(file));
) {
byte[] bs = new byte[1024];
int len;
response.reset(); // 非常重要
URL u = new URL("file:///" + "filePath");
String contentType = u.openConnection().getContentType();
response.setContentType(contentType);
response.setHeader("Content-Disposition", "inline;filename="
+ "preview.pdf");
out = response.getOutputStream();
while ((len = br.read(bs)) > 0) {
out.write(bs, 0, len);
}
out.flush();
out.close();
}
} catch (Exception e) {
e.printStackTrace();
}
}
此时 前端解析可直接拿返回的文件流 例子如下
let blob = this.response;
const binaryData = [];
binaryData.push(blob);
const url = window.URL.createObjectURL(new Blob(binaryData, { type: 'application/pdf' }));
window.open(url);
但有的时候 不想返回文件流 可把文件返回为base64 （注意 base64可能超长）此时代码修改如下
File file = new File("filePath");
OutputStream out = null;
try (BufferedInputStream br = new BufferedInputStream(new FileInputStream(file));
ByteArrayOutputStream outStream = new ByteArrayOutputStream();
) {
int len;
URL u = new URL("file:///" + "filePath");
String contentType = u.openConnection().getContentType();
byte[] buffer = new byte[1024];
//每次读取的字符串长度，如果为-1，代表全部读取完毕
//使用输入流从buffer里把数据读取出来
while ((len = br.read(buffer)) != -1) {
//用输出流往buffer里写入数据，中间参数代表从哪个位置开始读，len代表读取的长度
outStream.write(buffer, 0, len);
}
// 对字节数组Base64编码
Base64Encoder base64 = new Base64Encoder();
String base64Str = replaceEnter(base64.encode(outStream.toByteArray()));
}
} catch (Exception e) {
}
前端修改如下
let base64 = resBase64.data.base64;
base64 = base64.replace(/[\n\r]/g, '')
const raw = window.atob(base64)
const rawLength = raw.length
const uInt8Array = new Uint8Array(rawLength)
for (let i = 0; i < rawLength; ++i) {
uInt8Array[i] = raw.charCodeAt(i)
}
const url = window.URL.createObjectURL(new Blob([uInt8Array], { type: resBase64.data.contentType }));
window.open(url);
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