Question

我尝试将Book类型的对象插入数据库，其中一列被指定为日期，但根据此例外：

Caused by: org.postgresql.util.PSQLException: ERROR: column "publish_date" is of type date but expression is of type bytea
  Hint: You will need to rewrite or cast the expression.
  Position: 94
    at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:2412)
    at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:2125)
    at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:297)
    at org.postgresql.jdbc.PgStatement.executeInternal(PgStatement.java:428)
    at org.postgresql.jdbc.PgStatement.execute(PgStatement.java:354)
    at org.postgresql.jdbc.PgPreparedStatement.executeWithFlags(PgPreparedStatement.java:169)
    at org.postgresql.jdbc.PgPreparedStatement.executeUpdate(PgPreparedStatement.java:136)
    at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.executeUpdate(ResultSetReturnImpl.java:204)
    ... 11 more

正在以bytea形式输入。我不确定为什么会这样，因为在数据库中，列本身的类型是date，而我的Book类中的列是date类型。我可以在下面显示以下代码：

package examples.pubhub.model;

import java.time.LocalDate;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name="books")
public class Book {

    @Id
    @Column(name="isbn_13")
    public String isbn_13;  // International Standard Book Number, unique

    @Column(name="title")
    private String title;

    @Column(name="author")
    private String author;

    @Column(name="publish_date")
    private LocalDate publish_date; // Date of publish to the website

    @Column(name="price")
    private double price;

    @Column(name="content")
    private byte[] content;

    // Constructor used when no date is specified
    public Book(String isbn, String title, String author, byte[] content, double price) {
        super();
        this.isbn_13 = isbn;
        this.title = title;
        this.author = author;
        this.publish_date = LocalDate.now();
        this.content = content;
        this.price = price;
    }

    // Constructor used when a date is specified
    public Book(String isbn, String title, String author, LocalDate publishDate, double price, byte[] content) {
        super();
        this.isbn_13 = isbn;
        this.title = title;
        this.author = author;
        this.publish_date = publishDate;
        this.content = content;
        this.price = price;
    }

    // Default constructor
    public Book() {

    }

    public String getIsbn_13() {
        return isbn_13;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getAuthor() {
        return author;
    }

    public void setAuthor(String author) {
        this.author = author;
    }

    public LocalDate getPublish_date() {
        return publish_date;
    }


    public void setPublish_date(LocalDate publishDate) {
        this.publish_date = publishDate;
    }

    public double getPrice() {
        return price;
    }

    public void setPrice(double price) {
        this.price = price;
    }

    public byte[] getContent() {
        return content;
    }

    public void setContent(byte[] content) {
        this.content = content;
    }

    public void setIsbn_13(String isbn) {
        this.isbn_13 = isbn;

    }

}

这是我正在测试的离线课程：

package examples.pubhub.utilities;

import java.time.LocalDate;


import examples.pubhub.dao.BookDAO;
import examples.pubhub.dao.BooktagDAO;
import examples.pubhub.model.Book;
import examples.pubhub.model.Booktag;

public class PublishBookTest {

    public static void main(String[] args) {
        // TODO Auto-generated method stub

        String isbn = "1234123412341";
        String title = "Title";
        String author = "Haisam";
        String book_tag = "Science Fiction";


        BookDAO database = DAOUtilities.getBookDAO();
        Book tempBook = database.getBookByISBN(isbn);
        BooktagDAO tagdao = DAOUtilities.getBooktagDAO();
        Booktag tempBooktag = tagdao.getBookTagByISBN(isbn);

        if (tempBook != null && tempBooktag != null) {
            // ASSERT: book with isbn already exists

            System.out.println("ISBN already exists.");


        } else {

            Book book = new Book();
            Booktag booktag = new Booktag();
            book.setIsbn_13(isbn);
            book.setTitle(title);
            book.setAuthor(author);
            book.setPrice(124);
            book.setPublish_date(LocalDate.now());
            book.setContent(null);
            booktag.setBook_tag(book_tag);
            booktag.setBook_isbn(isbn);
            booktag.setBook_title(title);


            boolean isSuccess_booktag = tagdao.addTag(booktag);
            boolean isSuccess_book = database.addBook(book);



        if (isSuccess_book && isSuccess_booktag) {

            System.out.println("Added.");

        } else {

            System.out.println("Not added.");
        }


            }
        }

    }

如果有人知道如何从bytea转换为日期，或者这个问题的关键可能是什么，我将永远感激不尽。谢谢你的时间。

TLDR：由于LocalDate publish_date与数据库中的实际列publish_date（类型为date）之间的类型不兼容，因此事务未提交。不知道为什么。

Answer 1

创建LocalDateToWhateverDBTypeConverter。 Here就是这样。

修改：

有两种方法可以定义Converter的用法。第一个是在autoapply=true类的@Converter注释中设置Converter。在这种情况下，JPA提供程序将使用此Converter来转换给定类型的所有实体属性。如果autoapply设置为false，则需要将javax.persistence.Convert注释添加到要转换的所有属性并指定Converter类。以下代码段显示了此方法的示例：

@Entity public class RectangleEntity { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private Integer id; @Column private Integer x; @Column private Integer y; @Column @Convert(converter = ColorConverter.class) private Color color; ... }

错误：列＆＃34; publish_date＆＃34;是date类型，但表达式是bytea类型

1 个答案: