使用 jpa 从 postgres 读取 byte[] 时，长度几乎增加了一倍

发布于 2024-11-10 16:57:44 字数 1163 浏览 3 评论 0原文

我有一个 Image 类，它有一个 byte[] 来包含实际的图像数据。我可以在我的网络应用程序中上传和插入图像。当我尝试从 JPA 读取图像后显示图像时，我的 byte[] 的长度始终为 2x-1 或 2x-2，其中 x 是 postgres 9 中 bytea 字段的长度。显然浏览器不会显示图像说它已损坏。我需要一些帮助来弄清楚为什么我得到的结果是我预期的两倍。这是我的图像类的映射。在 Mac 上使用 eclipselink 和 JPA 2 来访问 postgres 9。

当我从数据库中选择时，

select *, length(bytes) from image;

我得到的长度为 9765。在控制器的断点中，byte[] 长度为 19529，比数据库中的两倍少一个字节。

@Entity
@Table( name = "image" )
@SequenceGenerator( name = "IMAGE_SEQ_GEN", sequenceName = "IMAGE_SEQUENCE" )
public class Image
        extends DataObjectAbstract<Long>
{
    @Id
    @GeneratedValue( strategy = GenerationType.SEQUENCE, generator = "IMAGE_SEQ_GEN" )
    private Long key;

    @Column( name="content_type" )
    private String contentType;

    @Lob
    @Basic( optional=false )
    @Column( name="bytes" )
    private byte[] bytes;

    // constructor and getters and setters

}

pgadmin 向我展示了以下图像表

CREATE TABLE image
(
  "key" bigint NOT NULL,
  bytes bytea,
  content_type character varying(255),
  "version" integer,
  CONSTRAINT image_pkey PRIMARY KEY (key)
)
WITH (
  OIDS=FALSE
);

原文

I have an Image class that has a byte[] to contain the actual image data. I'm able to upload and insert the image just fine in my webapp. When I attempt to display the image after reading it from JPA the length of my byte[] is always either 2x-1 or 2x-2, where x is the length of the bytea field in postgres 9. Obviously the browser won't display the image saying it's corrupted. I could use some help figuring out why I'm getting (about) twice what I expect. Here's the mapping of my image class. Using eclipselink with JPA 2 hitting postgres 9 on a mac.

When I select from the database with

select *, length(bytes) from image;

I get a length of 9765. In a breakpoint in my controller the byte[] length is 19529 which is one byte shy of twice what's in the database.

@Entity
@Table( name = "image" )
@SequenceGenerator( name = "IMAGE_SEQ_GEN", sequenceName = "IMAGE_SEQUENCE" )
public class Image
        extends DataObjectAbstract<Long>
{
    @Id
    @GeneratedValue( strategy = GenerationType.SEQUENCE, generator = "IMAGE_SEQ_GEN" )
    private Long key;

    @Column( name="content_type" )
    private String contentType;

    @Lob
    @Basic( optional=false )
    @Column( name="bytes" )
    private byte[] bytes;

    // constructor and getters and setters

}

pgadmin shows me the following for the image table

CREATE TABLE image
(
  "key" bigint NOT NULL,
  bytes bytea,
  content_type character varying(255),
  "version" integer,
  CONSTRAINT image_pkey PRIMARY KEY (key)
)
WITH (
  OIDS=FALSE
);

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