将BufferedInputStream转换为图像

我无法将我的blob变成缓冲图像，所以我可以使用它。 我从使用inputstream上传的数据库中获取blob（jpg图像）。 在我的数据库中，它存储为BufferedInputStream，我注意到了。 我得到的斑点很好，它是一堆奇怪的符号，并说它是一个jpg所以图像必须很好。 谁能发现我做错了什么？ 也许我转换它错了？ at image = ImageIO.read（new ByteArrayInputStream（data））; 图像返回null。

@GET @Path("{id}") @Produces("image/*") public Response post(@PathParam("id") String id) throws IOException { Connection con = connection(); Blob blob = getPhoto(con); BufferedImage image = null; byte[] data = null; int blobLength = 0; try { blobLength = (int) blob.length(); data = blob.getBytes(1, blobLength); image = ImageIO.read(new ByteArrayInputStream(data)); // ImageIO.write(image, "JPEG", new File("C:/Users/Nicolas/Desktop/image.jpg")); } catch (SQLException e2) { e2.printStackTrace(); } return Response.ok(image).build(); } 

我如何写入数据库

 public void postPhoto(Connection con, InputStream uploadedInputStream){ String mySQL = "INSERT INTO photos (photo) values (?)"; PreparedStatement pStmt = con.prepareStatement(mySQL); pStmt.setBlob(1, uploadedInputStream); pStmt.execute(); } 

我如何将文件发送到我的servlet

 var fileInput = document.getElementById('file'); var file = fileInput.files[0]; var formData = new FormData(); formData.append("file", file); var parameters="first="+firstName+"&last="+lastName+"&file="+file; xmlhttp.open("post","http://localhost:8080/restService/api/submitinfo",true); xmlhttp.setRequestHeader("Content-Type", "application/x-www-form-urlencoded"); xmlhttp.send(formData); 

Answer 1

首先validationuploadInputStream是否为有效映像，然后使用ImageIO.write写出来。 您始终可以使用ImageIO.read重新读取图像并将其写回ByteArrayInputStream ;）

我使用H2数据库进行了快速测试。

我注意到的一些事情。 Blob#length返回long ，而Blob#getBytes需要int ，这可能意味着你要截断字节流。

另外，根据H2的文档，似乎Blob内容不会保存在内存中，所以我使用getBinaryStream代替。

 import java.awt.image.BufferedImage; import java.io.ByteArrayInputStream; import java.io.ByteArrayOutputStream; import java.io.File; import java.io.IOException; import java.sql.Blob; import java.sql.Connection; import java.sql.DriverManager; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import javax.imageio.ImageIO; import javax.swing.ImageIcon; import javax.swing.JLabel; import javax.swing.JOptionPane; import javax.swing.JScrollPane; public class TestImageDatbase { private Connection con; public static void main(String[] args) { new TestImageDatbase(); } public TestImageDatbase() { try { clearDatabase(); saveImage(); loadImage(); } catch (ClassNotFoundException | SQLException | IOException exp) { exp.printStackTrace(); } } protected Connection getConnection() throws ClassNotFoundException, SQLException { Class.forName("org.h2.Driver"); return DriverManager.getConnection("jdbc:h2:d:\\Image", "sa", ""); } protected void clearDatabase() throws IOException, ClassNotFoundException, SQLException { Connection con = null; PreparedStatement stmt = null; try { con = getConnection(); System.out.println("Cleaning database"); stmt = con.prepareStatement("delete from images"); int updated = stmt.executeUpdate(); System.out.println("Updated " + updated + " rows"); } finally { try { stmt.close(); } catch (Exception e) { } try { con.close(); } catch (Exception e) { } } } protected void saveImage() throws IOException, ClassNotFoundException, SQLException { Connection con = null; PreparedStatement stmt = null; ByteArrayOutputStream baos = null; ByteArrayInputStream bais = null; try { baos = new ByteArrayOutputStream(); File source = new File("/path/to/file"); System.out.println("Source size = " + source.length()); BufferedImage img = ImageIO.read(source); ImageIO.write(img, "png", baos); baos.close(); bais = new ByteArrayInputStream(baos.toByteArray()); con = getConnection(); stmt = con.prepareStatement("insert into images (image) values (?)"); stmt.setBinaryStream(1, bais); int updated = stmt.executeUpdate(); System.out.println("Updated " + updated + " rows"); } finally { try { bais.close(); } catch (Exception e) { } try { baos.close(); } catch (Exception e) { } try { stmt.close(); } catch (Exception e) { } try { con.close(); } catch (Exception e) { } } } protected void loadImage() throws IOException, ClassNotFoundException, SQLException { Connection con = null; PreparedStatement stmt = null; ResultSet rs = null; try { con = getConnection(); stmt = con.prepareStatement("select image from images"); rs = stmt.executeQuery(); while (rs.next()) { System.out.println("Getting blob"); Blob blob = rs.getBlob(1); System.out.println("Reading image"); BufferedImage img = ImageIO.read(blob.getBinaryStream()); System.out.println("img = " + img); JOptionPane.showMessageDialog(null, new JScrollPane(new JLabel(new ImageIcon(img)))); } } finally { try { rs.close(); } catch (Exception e) { } try { stmt.close(); } catch (Exception e) { } try { con.close(); } catch (Exception e) { } } } }