使用java创建客户端文件

Question

i am trying to create a project which create a file in client side . i ave done the coding to create a file .but it obviously will be created in server side.. can any one help to do this. below is the code i have done..

    File file = new File("d:/file.txt");
        try {

            String content = "This is the content to write into file";
            if (!file.exists()) {
                file.createNewFile();
            }
            FileWriter fw = new FileWriter(file.getAbsoluteFile());
            BufferedWriter bw = new BufferedWriter(fw);
            bw.write(content);
            bw.close();
            System.out.println("Done");
        } catch (IOException e) {
            e.printStackTrace();
        }

I have also tried to create a file using filesysapi, which is done using HTML and javascript. but i got "Error: SECURITY_ERR"

Answer 1

using socket programming, 1st create a communication between server and client machines. Socket kkSocket = new Socket(hostName, portNumber) then use File file = new File("hostname@d:/file.txt");

if your host file does not contain hostname IP address maping, then instead of giving hostname, use IP address.

Answer 2

Despite what everyone is saying, you can create a client-side file via javascript. It's a sandboxed portion of the File System, done via HTML5's FileSystem API.

HOWEVER, my guess is your SECURITY_ERR is probably because you are opening an html page with the target javascript via File://PATH_TO_HTML_PAGE in your browser. The File-System API Will not work unless your grabbing the html/javascript/css from a server (like locahost:8080/test.html - Netbeans has some options to run a glassfish/server instance pretty painlessly locally on your machine if you have no experience with servers.).

Update 1-31-2014 Found this in an article on the File-System API , which confirmed the above paragraph for me:

You may need the --allow-file-access-from-files flag if you're debugging your app from file://. Not using these flags will result in a SECURITY_ERR or QUOTA_EXCEEDED_ERR FileError.

end update

That said, in the previous comment on a different question you asked and I answered , you were using TEMPORARY Storage. I use PERSISTENT because it is more reliable, and the browser displays a message asking for permission to store the data locally on the target machine. Here is how I have been making files locally on client machines for persistent data storage for the past couple years. This to the best of my knowledge only works with a handful of browser's, I use Google Chrome - the following defeinitely works in Google Chrome.

The following is javascript and needs to be within either an external script or script tags.

//this is a callback function that gets passed to your request for the file-System.
var onInitFs = function(fileSys){
    //fileSystem is a global variable
    fileSystem = fileSys;
    //once you have access to the fileSystem api, then you can create a file locally
    makeAFile();
    makeAndWriteContent();
};
var errorHandler = function(e){console.log('Error', e);};

//request 1 GB memory in a quota request
//note the internal callback `function(grantedBytes){...}` which makes the actual 
//request for the Filesystem, on success `onInitFs` is called. 
///on error the `errorHandler` is called
navigator.webkitPersistentStorage.requestQuota(1024*1024*1024*1, function(grantedBytes) {
    window.webkitRequestFileSystem(PERSISTENT, grantedBytes, onInitFs, errorHandler); 
}, errorHandler);

//this method will only work once the fileSystem variable has been initialized
function makeAFile(){
    var callbackFunctionOnSuccess = function(){console.log("created new file")}
    fileSystem.root.getFile("test.txt", {
        create: true
    }, callbackFunctionOnSuccess, function(error){console.log(error);});
}

function makeAndWriteContent(){
    //this is going to be passed as a callback function, to be executed after
    //contents are written to the test2.txt file.
    var readFile = function(){
       fileSystem.root.getFile("test2.txt", {create: false}, function(fileEntry) {
           fileEntry.file(function(file) {
              var reader = new FileReader();
              reader.onloadend = function(e) {
                console.log(this.result);
              };
              reader.readAsText(file);
           }, function(error){console.log(error);});
         }, function(error){console.log(error);});
    }


    fileSystem.root.getFile("test2.txt", {
        create: true
    }, function(fileEntry) {
        fileEntry.createWriter(function(writer) {
            writer.onwriteend = function(e) {
                writer.onwriteend = function(e){
                    //now, we will read back what we wrote.
                    readFile();
                }
                writer.onerror = function(e3){console.log(e3);
                }
                var blob = new Blob(["Hello World"]);
                writer.write(blob);
            };
            writer.onerror = function(e3) {console.log(e3);};
            //make sure our target file is empty before writing to it.
            writer.truncate(0);
        }, errorHandler);
    }, errorHandler);
}

One thing to keep in mind is that the File-System API is asynchronous so you have to get use to using callback functions. If you try to access the File-System API before it's instantiated, or if you try to access files before they are ready, you will also get errors. Callback functions are essential.

Answer 3

您无法在客户端创建文件，因为浏览器不允许这样做。