Java 如何查询blob？

我想创建返回一些值的SQL查询，其中一个值是blob

当我将blob列放入select时，它返回BigDecimal：|

它的普通JDBC查询带有参数插入

stmt = con.prepareStatement("INSERT INTO TABLE(fileName, "
            + "blobData) VALUES(?, ?)");
        stmt.setString(1, "somefilename");
        stmt.setObject(2, data);//data is byte[]
        stmt.executeUpdate();

选择

ResultSet rs;

    stmt = con.prepareStatement("SELECT blobData "
        + "FROM BlobTest " + "WHERE fileName = ?");

    stmt.setString(1, "somevalue");
    rs = stmt.executeQuery();
    if (!rs.next()) {
      System.out.println("No such file stored.");
    } else {
      Blob b = rs.getBlob(1);
      BufferedOutputStream os;

插入

stmt = con.prepareStatement("INSERT INTO TABLE(fileName, "
            + "blobData) VALUES(?, ?)");
        stmt.setString(1, "somefilename");
        stmt.setObject(2, data);//data is byte[]
        stmt.executeUpdate();

选择

ResultSet rs;

    stmt = con.prepareStatement("SELECT blobData "
        + "FROM BlobTest " + "WHERE fileName = ?");

    stmt.setString(1, "somevalue");
    rs = stmt.executeQuery();
    if (!rs.next()) {
      System.out.println("No such file stored.");
    } else {
      Blob b = rs.getBlob(1);
      BufferedOutputStream os;

---

尝试从结果集调用getBytes（）方法：

stmt = dbConn.prepareStatement("SELECT ...");
ResultSet rs = stmt.executeQuery();
byte[] blob = rs.getBytes(1);

---

这将以字节数组的形式返回blob对象。
尝试从结果集调用getBytes（）方法：

stmt = dbConn.prepareStatement("SELECT ...");
ResultSet rs = stmt.executeQuery();
byte[] blob = rs.getBytes(1);

---

这将以字节数组的形式返回blob对象。
请查看上的javadocs部分
您需要在blob列上调用

getBlob

，然后读取二进制流

    Blob blob = rs.getBlob("BLOB_COLUMN_NAME");        
    InputStream blobStream = blob.getBinaryStream();

    //e.g. save blob to a file
    FileOutputStream out = new FileOutputStream("file.txt");
    byte[] buffer = new byte[1024];
    int n = 0;  
    while( (n = blobStream.read(buffer)) != -1 ) {
        out.write(buffer, 0, n);
    }
    out.flush();
    out.close();
    blobStream.close();

---

请看上的javadocs部分
您需要在blob列上调用

getBlob

，然后读取二进制流

    Blob blob = rs.getBlob("BLOB_COLUMN_NAME");        
    InputStream blobStream = blob.getBinaryStream();

    //e.g. save blob to a file
    FileOutputStream out = new FileOutputStream("file.txt");
    byte[] buffer = new byte[1024];
    int n = 0;  
    while( (n = blobStream.read(buffer)) != -1 ) {
        out.write(buffer, 0, n);
    }
    out.flush();
    out.close();
    blobStream.close();

实际上，setBytes（）（而不是setObject（））可能更便于移植。但这在很大程度上取决于JDBC驱动器，因此setBytes（）（而不是setObject（））可能更具可移植性。但这在很大程度上取决于JDBC驱动程序