通过第三方接口，后端返回字节流给前端预览PDF

后端：

public void qryPdfInfo(HttpServletResponse response) {
    // 实例化对象
    HttpClient client = new HttpClient();
    GetMethod get = null;
    OutputStream output = null;
    try {
        List
 headers = new ArrayList<>();
        // 第三方接口请求头
        headers.add(new Header("Cookie", cookie));
        get = new GetMethod("第三方接口请求url");
        client.getHostConfiguration().getParams().setParameter(
                "http.default-headers", headers);
        if (200 == client.executeMethod(get)) {
            output = response.getOutputStream();
            byte[] responseBody = get.getResponseBody();
            output.write(responseBody);
            output.flush();
        }
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        // 关流
        try {
            if(output != null){
                output.close();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        get.releaseConnection();
        client.getHttpConnectionManager().closeIdleConnections(0);
    }
}

前端JS：

使用ajax请求打开的pdf是空白的，这里采用xhr

var url = "本地接口url";
var xhr = new XMLHttpRequest();
xhr.open('POST', url, true);
xhr.responseType = "blob";  // 返回类型blob
xhr.onload = function () {
    // this.response 是返回的流数据
    var blob = new Blob([this.response], {
        type: 'application/pdf;chartset=UTF-8'
    })
    var fileURL= URL.createObjectURL(blob)
    $("#pdf").attr("src", fileURL)
    window.open(fileURL)
};
xhr.send()

前端页面：

在页面中加入pdf标签