java - MySQL 插入数据时出现错误 "Duplicate entry ' ' for key "

Question

我的模型类:

LetterDoc.java

@Entity
@Table(name = "letter_doc")
public class LetterDoc implements Serializable {


    private static final long serialVersionUID = 1L;

    @Id
    TwoP twoP;


    private String docFile;

    //i ommited getters and setters
    public LetterDoc() {

    }

Document.java

@Entity
@Table(name = "document")
public class Document {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long docId;

    private String docName;

    @Transient
    private boolean checked=false;

    public Document() {

    }

TwoP.java

@Embeddable
public class TwoP implements Serializable {

    @ManyToOne(fetch = FetchType.EAGER, optional = false,cascade=CascadeType.PERSIST)
    @JoinColumn(name = "letterNo",unique=true)
    @JsonIgnore
    private Letter letter;

    @ManyToOne(fetch = FetchType.EAGER, optional = false,cascade=CascadeType.PERSIST)
    @JoinColumn(name = "documentId",unique=true)
    @JsonIgnore
    private Document document;

    public TwoP(Letter letter, Document document) {

        this.letter = letter;
        this.document = document;
    }

    public TwoP() {

    }


}

我从客户端发送到 api 的 json 数据是:

在我的 api 中，我使用此方法来使用 json 数据:

@PostMapping(value = "/letter/create", produces = MediaType.APPLICATION_JSON_VALUE)
    public SLDto postAllOne(@RequestBody SLDto sldto) {

Letter letter = letterRepository.save(new Letter(clkLetter, sldto.getLetterDto().getInOut(),
                sldto.getLetterDto().getInOutNo(), sldto.getLetterDto().getInOutDate(),
                sldto.getLetterDto().getLetterIssuedSubBy(), sldto.getLetterDto().getLetterFile(),
                sldto.getLetterDto().getRepresentativeName(), selection, assessment));
    //Please consider letter is inserted with Id no 22.

            for (DocumentDto documentDto : sldto.getDocumentDto()) {
                TwoP twoP = null;
                LetterDoc letterDoc = null;

                System.out.println("loopedonce");
                Document document = null;
                System.out.println("total documents Id is" + documentDto.getDocId());
                document = documentRepository.findById((long) documentDto.getDocId()).get();
                System.out.println("Document Id from db is" + document.getDocId());
                twoP = new TwoP(letter, document);
                letterDoc = new LetterDoc();
                letterDoc.setTwoP(twoP);
                letterDoc.setDocFile(null);
                letterDocRepository.save(letterDoc);
                     } 
}

SlDto.java类

private LetterDto letterDto;
    private List<DocumentDto> documentDto;
    private List<SelectionCustomOfficeDto> selectionCustomOfficeDto;

现在在我上面使用的For循环中，它必须循​​环两次，因为传入的Json数据数量是Two。是的，它循环两次，在这一行中document = documentRepository. findById((long) documentDto.getDocId()).get(); ，我两次获取 Document 对象，但是当将其插入 letterDocRepository.save(letterDoc); 时，它显示了我

Duplicate entry '22' for key 'UK_5pahc9x5lwh5k4owpm3vjfq3c'

“22”是我插入“letter”表时创建的最新 ID

由于我的 documentDto.getDocId() 返回来自 JSON 数据的 1,2，尽管它们不同，但程序向我显示错误。

为了了解发生了什么，我调试了它们以查看数据是否从数据库到达:

错误是:

com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Duplicate entry '22' for key 'UK_5pahc9x5lwh5k4owpm3vjfq3c'
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[na:1.8.0_161]
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source) ~[na:1.8.0_161]
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source) ~[na:1.8.0_161]
    at java.lang.reflect.Constructor.newInstance(Unknown Source) ~[na:1.8.0_161]
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:425) ~[mysql-connector-java-5.1.47.jar:5.1.47]
    at com.mysql.jdbc.Util.getInstance(Util.java:408) ~[mysql-connector-java-5.1.47.jar:5.1.47]
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:936) ~[mysql-connector-java-5.1.47.jar:5.1.47]

Answer 1

我认为您的问题来自于Cascade属性行为，使用Persist它会在您保存letterDoc对象时尝试插入它。 尝试改用cascade.MERGE。

如果您想要 Persist，请不要插入您使用 cascade.persist 声明的任何关联，因为 Hibernate 会为您执行此操作。