postgresql插入和读取图片

postgresql存储图片需要二进制类型bytea，创建一张测试表：

postgres=# create table test_image(img bytea);
CREATE TABLE
使用jdbc插入1.jpg
try {
    connection = JDBCUtil.getConnection();
    connection.setAutoCommit(false);
    String sql = "INSERT INTO test_image(img) VALUES(?)";
    preparedStatement = connection.prepareStatement(sql);
    InputStream inputStream = new FileInputStream(img_name);
    preparedStatement.setBinaryStream(1,inputStream);
    preparedStatement.executeUpdate();
    connection.commit();
} catch (SQLException | FileNotFoundException e) {
    throw new RuntimeException(e);
} finally {
    JDBCUtil.release(connection);
查看字段长度
postgres=# select length(img) from test_image;
 length
--------
  50726
(1 row)
try {
    connection = JDBCUtil.getConnection();
    String sql = "SELECT img from test_image";
    preparedStatement = connection.prepareStatement(sql);
    resultSet = preparedStatement.executeQuery();
    while (resultSet.next()) {
        InputStream in = resultSet.getBinaryStream(1);
        byte[] buffer = new byte[1024*1024];
        OutputStream out = new FileOutputStream("new_1.jpg");
        for (int i; (i = in.read(buffer)) > 0;)
            out.write(buffer, 0, i);
            out.flush();
        out.close();
        in.close();
} catch (Exception e) {
    e.printStackTrace();
} finally {
    JDBCUtil.release(connection);