java - 如何将 iputStream 转换为字符串并通过 filemap 获取

Question

我正在尝试将多个图像插入数据库。我正在插入与以下类型匹配的图像

我的表:

  `Sno` int(11) NOT NULL AUTO_INCREMENT,
  `Class` varchar(45) DEFAULT NULL,
  `Subject` varchar(45) DEFAULT NULL,
  `CreatedBy` varchar(45) DEFAULT NULL,
  `QimgName` varchar(45) DEFAULT NULL,
  `Qimg` mediumblob,
  `AimgName` varchar(45) DEFAULT NULL,
  `Aimg` mediumblob,
  PRIMARY KEY (`Sno`)

MyJsp.jsp

<form action="MatchImgTImgUpload" method="post" enctype="multipart/form-data">
<div id="container" >
 <div>
  <img alt="Image1" id="Image1" src="" width="130px" height="90px"><br><br>
  <img alt="Image2" id="Image2" src="" width="130px" height="90px"><br><br>
  <img alt="Image3" id="Image3" src="" width="130px" height="90px"><br><br> 
  <img alt="Image4" id="Image4" src="" width="130px" height="90px"><br><br>
  <img alt="Image5" id="Image5" src="" width="130px" height="90px"><br><br>
  </div>

  <div>
  <img alt="Image6" id="Image6" src="" width="130px" height="90px"><br><br>
  <img alt="Image7" id="Image7" src="" width="130px" height="90px"><br><br>
  <img alt="Image8" id="Image8" src="" width="130px" height="90px"><br><br> 
  <img alt="Image9" id="Image9" src="" width="130px" height="90px"><br><br>
  <img alt="Image10" id="Image10" src="" width="130px" height="90px"><br><br>
  </div>

</div>
<input type="file"  id="files1" name="files1[]" value="Upload Questions" multiple>
<input type="file"  id="files2" name="files2[]" value="Upload Answers" multiple>
<input type="submit" value="AddToDB?">
</form>

MatchImgTImgUpload.java :

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        String clas="I",subject="EVS",uid="112";
        Connection con = null;
        List<String> listGet = new ArrayList<String>();
        List<String> listGet2 = new ArrayList<String>();

        System.out.println("Entered successfully:");
        final FileItemFactory factory = new DiskFileItemFactory();
        final ServletFileUpload fileUpload = new ServletFileUpload(factory);
        List items = null;
        //System.out.println("if0 successfully:");
         Map<String, InputStream> fileMap = new HashMap<String, InputStream>();
         //System.out.println("if0 successfully:");
        if (ServletFileUpload.isMultipartContent(request)) {
            //System.out.println("if0 successfully:");
            // get the request content and iterate through

            try {
                items = fileUpload.parseRequest(request);
            } catch (FileUploadException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            System.out.println("selected images :"+items);
            if (items != null) {
                //System.out.println("if0 successfully:");
                final Iterator iter = items.iterator();
                while (iter.hasNext()) {
                    //System.out.println("while successfully:");
                    final FileItem item = (FileItem) iter.next();
                    // this is for non-file fields
                    if (item.isFormField()) {
                        //System.out.println("if1 successfully:");

                    // logic for setting non-file fields
                    } else {
                        // item.getName() - gives file name
                        fileMap.put(item.getName(), item.getInputStream());
                        System.out.println("else successfully:"+item.getName());
                        System.out.println("else successfully:"+item.getInputStream());
                        listGet.add(item.getName());

                        String val = item.getInputStream().toString();
                        listGet2.add(val);

                    }
                }
            }
        }
        else
        {
             System.out.println("else successfully:");
        }

        try {
            //System.out.println("try successfully:");

        try {



        Class.forName("com.mysql.jdbc.Driver");
        } catch (ClassNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }       

        con = DriverManager.getConnection("jdbc:mysql://localhost:3306/raptor1_5","root","");


        Set<String> keySet = fileMap.keySet();
        int listgetcount = 0;
        int count2 =5;
        for (int k=1;k<=5;k++) {
            System.out.println("for successfully:");
        String sql ="INSERT INTO tbl_MatchImgToImg (Class, Subject, CreatedBy, QimgName, Qimg, AimgName, Aimg) values (?, ?, ?, ?, ?, ?, ?)" ; 
        PreparedStatement statement;

            statement = con.prepareStatement(sql);

             statement.setString(1, clas);  
             statement.setString(2, subject);
             statement.setString(3, uid); 

             statement.setString(4, listGet.get(listgetcount));    


             String getval = listGet2.get(listgetcount);

             statement.setBlob(5, fileMap.get(getval));



             statement.setString(6, listGet.get(count2));    

             String getval2 = listGet2.get(count2);
             statement.setBlob(7, fileMap.get(getval2));


            int row = statement.executeUpdate();

            System.out.println("inserted successfully:");
            listgetcount = listgetcount+1;
            count2=count2+1;
        }
        listgetcount=0;
        }
         catch (SQLException e) {
            // TODO Auto-generated catch block
            System.out.println("errror is:"+e);
        }  
         finally{
             try {

                con.close();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
         }


    }

它的插入如下，

我正在尝试的是，有 10 张(左侧图像 5 和右侧图像 5)图像，但我必须插入，例如第 1 张图像(左)是问题，第 6 张(右)图像是第 1 张图像的答案想插入第 5 张图片是问题，第 10 张图片是第 5 张图片的答案。从上面的代码中，除了 statement.setBlob(5, fileMap.get(getval)); 和 statement.setBlob(7, fileMap.get(getval2)); 因为它的值得到 null 值。

我猜这个问题是因为转换 String val = item.getInputStream().toString();listGet2.add(val); 所以请有人帮助我。

连我都试过了，

statement.setBlob(5, fileMap.get(0));statement.setBlob(7, fileMap.get(5));

但是没有用，希望有人指出我的错误。

更新:

我在这里更新了我的问题取决于下面发布的答案。我尝试了你的代码，即使我卡在了代码中，

private DataSource dataSource;

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String clas="I",subject="EVS",uid="112";

        List<String> listGet = new ArrayList<String>();

        FileItemFactory factory = new DiskFileItemFactory();
        ServletFileUpload fileUpload = new ServletFileUpload(factory);

        if (!ServletFileUpload.isMultipartContent(request)) {
            throw new RuntimeException("..."); // ...or return a HTTP 400
        }

        // Collecting what's in the request
        Map<String, byte[]> contents = new HashMap<String, byte[]>();
        List<FileItem> items = fileUpload.parseRequest(request);
        for (FileItem item : items) {
            if (!item.isFormField()) {
                contents.put(item.getFieldName(), item.get());
                listGet.add(item.getFieldName());
            }
        }

        try (Connection connection = ((Statement) dataSource).getConnection()) {
            try (PreparedStatement stmt = connection.prepareStatement("INSERT INTO tbl_MatchImgToImg (Class, Subject, CreatedBy, QimgName, Qimg, AimgName, Aimg) values (?, ?, ?, ?, ?, ?, ?)")) {
                // For this part, you'll need Google Guava - but you can write your own checkNotNull(), too
               int answerimgcount = 5;
                for(int k=0;k<=4;k++){
                byte[] image1 = Preconditions.checkNotNull(contents.get("field1"),
                        "...error: invalid request, missing field1...");
                byte[] image2 = Preconditions.checkNotNull(contents.get("field2"),
                        "...error: invalid request, missing field2...");
                // ...
                stmt.setString(1, clas);    
                stmt.setString(2, subject);
                stmt.setString(3, uid); 

                stmt.setString(4, listGet.get(k));
                // ...
                stmt.setBytes(5, image1);
                // ...
                stmt.setString(6, listGet.get(answerimgcount));
                stmt.setBytes(7, image2);

                answerimgcount =answerimgcount+1;
               }
            }
        }
}

它显示如下图所示的错误，

无论我给出什么修复上面的代码不起作用，所以现在告诉我哪里错了!

即使我简单地尝试过，

List<String> listGet = new ArrayList<String>();

        FileItemFactory factory = new DiskFileItemFactory();
        ServletFileUpload fileUpload = new ServletFileUpload(factory);

        if (!ServletFileUpload.isMultipartContent(request)) {
            throw new RuntimeException("..."); // ...or return a HTTP 400
        }

        // Collecting what's in the request
        Map<String, byte[]> contents = new HashMap<String, byte[]>();
        List<FileItem> items = null;
        try {
            items = fileUpload.parseRequest(request);
        } catch (FileUploadException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        for (FileItem item : items) {
            if (!item.isFormField()) {
                contents.put(item.getName(), item.get());
                listGet.add(item.getName());
            }
        }

            int answerimgcount = 5;
                for(int k=0;k<=4;k++){
                System.out.println("imageName successfully:"+listGet.get(k));
                byte[] image1 = contents.get("field1");
                System.out.println("image1 successfully:"+image1);
                System.out.println("imageName successfully:"+listGet.get(answerimgcount));
                byte[] image2 =contents.get("field2");
                System.out.println("image1 successfully:"+image2);          


                answerimgcount =answerimgcount+1;
               }

但是 OP :

imageName successfully:image1.jpg
image1 successfully:null
imageName successfully:image6.jpg
image1 successfully:null
imageName successfully:image2.jpg
image1 successfully:null
imageName successfully:image7.jpg
image1 successfully:null
imageName successfully:image3.jpg
image1 successfully:null
imageName successfully:image8.jpg
image1 successfully:null
imageName successfully:image4.jpg
image1 successfully:null
imageName successfully:image9.jpg
image1 successfully:null
imageName successfully:image5.jpg
image1 successfully:null
imageName successfully:image10.jpg
image1 successfully:null
imageName successfully:
image1 successfully:null

Answer 1

我认为项目为 null 是您问题中最少的(实际上只是您的代码过于复杂和困惑的副作用 - 抱歉这么说)。

具体问题:

• 使用了很多不必要的数据结构(列表和映射)
• 对这些列表的内容做出大量假设
• 在应该检查空值时不检查
• 在不必要时检查空值(如果深入研究，parseRequest() 永远不会返回空值)
• InputStream.toString() 是错误的...它是一个字节流，您不应该只是将它转换为 Unicode 字符串(特别是因为您将它们作为 blob 存储在数据库中，也是)
• 不应捕获和忽略导致无法继续处理的错误(FileUploadException)
• 使用 System.out 而不是日志框架
• 如果无法建立连接，finally() 将失败并出现 NPE - 如果可以，最好使用 Java7 的 try-with block ，或 Apache Commons 的 IOUtils.closeQuietly()
• 使用 InputStreams 需要多加注意，因为它们只能被读取一次。我建议改为以 byte[] 形式获取数据(数据库驱动程序可能无论如何都会这样做)。

现在，让我们稍微清理一下:

// This one SHOULD be dependency injected... opening DB connections on your own
// rather than relying on a connection pool will lead to all sorts of problems
private DataSource dataSource;

protected void doPost2(HttpServletRequest request, HttpServletResponse response) throws ServletException,
        IOException, SQLException, FileUploadException {

    // I'd rather get these dependency-injected
    FileItemFactory factory = new DiskFileItemFactory();
    ServletFileUpload fileUpload = new ServletFileUpload(factory);

    if (!ServletFileUpload.isMultipartContent(request)) {
        throw new RuntimeException("..."); // ...or return a HTTP 400
    }

    // Collecting what's in the request
    Map<String, byte[]> contents = new HashMap<>();
    List<FileItem> items = fileUpload.parseRequest(request);
    for (FileItem item : items) {
        if (!item.isFormField()) {
            contents.put(item.getFieldName(), item.get());
        }
    }

    try (Connection connection = dataSource.getConnection()) {
        try (PreparedStatement stmt = connection.prepareStatement("...insert sql here...")) {
            // For this part, you'll need Google Guava - but you can write your own checkNotNull(), too
            byte[] image1 = Preconditions.checkNotNull(contents.get("field1"),
                    "...error: invalid request, missing field1...");
            byte[] image2 = Preconditions.checkNotNull(contents.get("field2"),
                    "...error: invalid request, missing field2...");
            // ...

            stmt.setString(1, "...");
            // ...
            stmt.setBytes(4, image1);
            // ...
            stmt.setString(6, "...");
            stmt.setBytes(7, image2);
        }
    }
}