Question

我有一个包含字段NAME的数据库，我需要在PICTURE等于文件名的每个实体上将图片作为blob类型上传到字段NAME。但是，在运行代码时会创建一堆具有重复NAME字段和PICTURE字段的新实体。这是我的代码：

主要

public static void main(String[] args) {
    File currentDir = new File("C:\\Users\\luccaskammer\\Desktop\\Imagens\\"); // Define o diretorio a ser lido
    displayDirectoryContents(currentDir);
}

public static void displayDirectoryContents(File dir) {
    try {

        ImagensParaDBController contr = new ImagensParaDBController();
        File[] files = dir.listFiles();
        DeletePng del = new DeletePng();
        //ConvertData conv = new ConvertData();

        for (File file: files) {

            ImagensParaBD img = new ImagensParaBD();
            ImagensParaBD name = new ImagensParaBD();
            ImagensParaBD picture = new ImagensParaBD();

            if (file.isDirectory())
            {
                System.out.println("directory:" + file.getCanonicalPath());
                displayDirectoryContents(file);
            }

            else if (file.isFile()) {
                System.out.println("     file:" + file.getCanonicalPath());
                img.setName(del.deletePng(file.getName()));
                java.nio.file.Path filelocation = Paths.get(file.getCanonicalPath());
                img.setPicture(Files.readAllBytes(filelocation));
                contr.insertImageDB(img, picture, name);
            }

            else {
                System.out.println("invalid");
            }
        }

        contr.disconnect();

    }
    catch(IOException e) {}
}

豆

@Entity
@Table(name = "planegeo")

public class ImagensParaBD implements Serializable {@Id@GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id;
    //private String pathFolder;
    private String name;@Lob
    private byte[] picture;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public byte[] getPicture() {
        return picture;
    }

    public void setPicture(byte[] picture) {
        this.picture = picture;
    }
}

控制器：

public class ImagensParaDBController {

    EntityManagerFactory mf = Persistence.createEntityManagerFactory("mySQLPU");
    EntityManager em = mf.createEntityManager();

    public void insertImageDB(ImagensParaBD img, ImagensParaBD name, ImagensParaBD picture) {

        em.getTransaction().begin();
        em.merge(img);
        em.getTransaction().commit();

    }

    public void disconnect() {

        em.close();
    }

    public void insertImageDB(ImagensParaBD img) {
        throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
    }
}

Answer 1

问题是您是否创建了新实例。相反，您必须从DB检索所有ImagensParaBD，其中name = required。

你新创建的实例没有id，所以hibernate只是插入它们。

List<ImagensParaBD> all = em.createQuery("Select a From ImagensParaBD a where name=:name", 
ImagensParaBD.class)
.setParameter("name", theNameTOFind)
.getResultList();

然后迭代添加信息并合并它们的实例

Answer 2

JPA将尝试从ID中查找数据库行对象。如果您的Id与数据库ID相同，则唯一的JPA合并该行。

这里你只传递图片对象。所以首先尝试从数据库中查找对象。如果它存在于数据库中，则在对象中获取ID和setID。我会工作的。

示例代码：

Query queryName= em.createQuery(from table_name where picture = :picture);
queryName.setParameter("picture",your picture Object);

list<ImagensParaBD> result = queryName.getResultList();
ImagensParaBD imagensParaBD = new ImagensParaBD();
imagensParaBD = result.get(0);
em.merge(imagensParaBD);

JPA合并是插入而不是更新

2 个答案: