例如，假设你有一个表存储图像的文件名， 并且你还想把图像本身存储在一个 bytea 列中：

CREATE TABLE images (imgname text, img bytea);

要插入一幅图像，你可以使用：

File file = new File("myimage.gif");
FileInputStream fis = new FileInputStream(file);
PreparedStatement ps = conn.prepareStatement("INSERT INTO images VALUES (?, ?)");
ps.setString(1, file.getName());
ps.setBinaryStream(2, fis, file.length());
ps.executeUpdate();
ps.close();
fis.close();

这里，setBinaryStream() 从一个流向 bytea 类型的列传输指定数量 的字节。如果图像的内容已经在一个 byte[] 中，这也可以用 setBytes() 方法来完成。

检索一幅图像甚至更容易。（我们在这里使用 PreparedStatement，但同样可以使用 Statement 类。）

PreparedStatement ps = con.prepareStatement("SELECT img FROM images WHERE imgname = ?");
ps.setString(1, "myimage.gif");
ResultSet rs = ps.executeQuery();
if (rs != null) {
    while (rs.next()) {
        byte[] imgBytes = rs.getBytes(1);
        // use the data in some way here
    }
    rs.close();
}
ps.close();

这里二进制数据是作为 byte[] 检索的。你也可以 改用一个 InputStream 对象。

又或者，你要存储一个非常大的文件，并想使用 LargeObject API 来 存储该文件：

CREATE TABLE imageslo (imgname text, imgoid oid);

要插入一幅图像，你可以使用：

// All LargeObject API calls must be within a transaction block
conn.setAutoCommit(false);

// Get the Large Object Manager to perform operations with
LargeObjectManager lobj = ((org.postgresql.PGConnection)conn).getLargeObjectAPI();

// Create a new large object
int oid = lobj.create(LargeObjectManager.READ | LargeObjectManager.WRITE);

// Open the large object for writing
LargeObject obj = lobj.open(oid, LargeObjectManager.WRITE);

// Now open the file
File file = new File("myimage.gif");
FileInputStream fis = new FileInputStream(file);

// Copy the data from the file to the large object
byte buf[] = new byte[2048];
int s, tl = 0;
while ((s = fis.read(buf, 0, 2048)) > 0) {
    obj.write(buf, 0, s);
    tl += s;
}

// Close the large object
obj.close();

// Now insert the row into imageslo
PreparedStatement ps = conn.prepareStatement("INSERT INTO imageslo VALUES (?, ?)");
ps.setString(1, file.getName());
ps.setInt(2, oid);
ps.executeUpdate();
ps.close();
fis.close();

从大对象中检索该图像：

// All LargeObject API calls must be within a transaction block
conn.setAutoCommit(false);

// Get the Large Object Manager to perform operations with
LargeObjectManager lobj = ((org.postgresql.PGConnection)conn).getLargeObjectAPI();

PreparedStatement ps = con.prepareStatement("SELECT imgoid FROM imageslo WHERE imgname = ?");
ps.setString(1, "myimage.gif");
ResultSet rs = ps.executeQuery();
if (rs != null) {
    while (rs.next()) {
        // Open the large object for reading
        int oid = rs.getInt(1);
        LargeObject obj = lobj.open(oid, LargeObjectManager.READ);

        // Read the data
        byte buf[] = new byte[obj.size()];
        obj.read(buf, 0, obj.size());
        // Do something with the data read here

        // Close the object
        obj.close();
    }
    rs.close();
}
ps.close();