如何使用 JPA 和 Hibernate 映射 PostgreSQL 枚舉

Question

我正在嘗試將名為傳輸結果的 postgres 自定義類型映射到 Hibernate/JPA POJO。 postgres 自定義類型或多或少是字符串值的枚舉類型。

我創建了一個名為 PGEnumUserType 的自定義 EnumUserType 以及一個表示 postgres 枚舉值的枚舉類。 當我針對真實數據庫運行此程序時，收到以下錯誤：“錯誤：列“狀態”的類型為傳輸結果，但表達式的類型為字符變化 提示：您需要重寫或轉換表達式。 位置：135'

看到這一點，我想我需要將我的 SqlTypes 更改為 Types.OTHER。 但是這樣做會破壞我的集成測試（在內存數據庫中使用 HyperSQL）並顯示以下消息：'Caused by: java.sql.SQLException: Table not found in statement [selectenrollment0_."id" as id1_47_0_,enrollment0_."tpa_approval_id" as tpa2_47_0_ ，enrollment0_."tpa_status_code" as tpa3_47_0_，enrollment0_."status_message" 作為 status4_47_0_，enrollment0_."approval_id" 作為批准5_47_0_，enrollment0_."transmission_date" 作為 transmis6_47_0_，enrollment0_作為傳輸_47_0_，"status_40_8"transmission_4itter0"status_7"statter0"status_7"傳輸“注冊0_其中注冊0_.“id”=？]'

我不確定為什么更改 sqlType 會導致此錯誤。 任何幫助表示贊賞。

JPA/休眠實體：

@Entity
@Access(javax.persistence.AccessType.PROPERTY)
@Table(name="transmissions")
public class EnrollmentCycleTransmission {

// elements of enum status column
private static final String ACCEPTED_TRANSMISSION = "accepted";
private static final String REJECTED_TRANSMISSION = "rejected";
private static final String DUPLICATE_TRANSMISSION = "duplicate";
private static final String EXCEPTION_TRANSMISSION = "exception";
private static final String RETRY_TRANSMISSION = "retry";

private Long transmissionID;
private Long approvalID;
private Long transmitterID;
private TransmissionStatusType transmissionStatus;
private Date transmissionDate;
private String TPAApprovalID;
private String TPAStatusCode;
private String TPAStatusMessage;


@Column(name = "id")
@Id
@GeneratedValue(strategy=GenerationType.AUTO)
public Long getTransmissionID() {
    return transmissionID;
}

public void setTransmissionID(Long transmissionID) {
    this.transmissionID = transmissionID;
}

@Column(name = "approval_id")
public Long getApprovalID() {
    return approvalID;
}

public void setApprovalID(Long approvalID) {
    this.approvalID = approvalID;
}

@Column(name = "transmitter")
public Long getTransmitterID() {
    return transmitterID;
}

public void setTransmitterID(Long transmitterID) {
    this.transmitterID = transmitterID;
}

@Column(name = "status")
@Type(type = "org.fuwt.model.PGEnumUserType" , parameters ={@org.hibernate.annotations.Parameter(name = "enumClassName",value = "org.fuwt.model.enrollment.TransmissionStatusType")} )
public TransmissionStatusType getTransmissionStatus() {
    return this.transmissionStatus ;
}

public void setTransmissionStatus(TransmissionStatusType transmissionStatus) {
    this.transmissionStatus = transmissionStatus;
}

@Column(name = "transmission_date")
public Date getTransmissionDate() {
    return transmissionDate;
}

public void setTransmissionDate(Date transmissionDate) {
    this.transmissionDate = transmissionDate;
}

@Column(name = "tpa_approval_id")
public String getTPAApprovalID() {
    return TPAApprovalID;
}

public void setTPAApprovalID(String TPAApprovalID) {
    this.TPAApprovalID = TPAApprovalID;
}

@Column(name = "tpa_status_code")
public String getTPAStatusCode() {
    return TPAStatusCode;
}

public void setTPAStatusCode(String TPAStatusCode) {
    this.TPAStatusCode = TPAStatusCode;
}

@Column(name = "status_message")
public String getTPAStatusMessage() {
    return TPAStatusMessage;
}

public void setTPAStatusMessage(String TPAStatusMessage) {
    this.TPAStatusMessage = TPAStatusMessage;
}
}

自定義枚舉用戶類型：

public class PGEnumUserType implements UserType, ParameterizedType {

private Class<Enum> enumClass;

public PGEnumUserType(){
    super();
}

public void setParameterValues(Properties parameters) {
    String enumClassName = parameters.getProperty("enumClassName");
    try {
        enumClass = (Class<Enum>) Class.forName(enumClassName);
    } catch (ClassNotFoundException e) {
        throw new HibernateException("Enum class not found ", e);
    }

}

public int[] sqlTypes() {
    return new int[] {Types.VARCHAR};
}

public Class returnedClass() {
    return enumClass;
}

public boolean equals(Object x, Object y) throws HibernateException {
    return x==y;
}

public int hashCode(Object x) throws HibernateException {
    return x.hashCode();
}

public Object nullSafeGet(ResultSet rs, String[] names, Object owner) throws HibernateException, SQLException {
    String name = rs.getString(names[0]);
    return rs.wasNull() ? null: Enum.valueOf(enumClass,name);
}

public void nullSafeSet(PreparedStatement st, Object value, int index) throws HibernateException, SQLException {
    if (value == null) {
        st.setNull(index, Types.VARCHAR);
    }
    else {
        st.setString(index,((Enum) value).name());
    }
}

public Object deepCopy(Object value) throws HibernateException {
    return value;
}

public boolean isMutable() {
    return false;  //To change body of implemented methods use File | Settings | File Templates.
}

public Serializable disassemble(Object value) throws HibernateException {
    return (Enum) value;
}

public Object assemble(Serializable cached, Object owner) throws HibernateException {
    return cached;
}

public Object replace(Object original, Object target, Object owner) throws HibernateException {
    return original;
}

public Object fromXMLString(String xmlValue) {
    return Enum.valueOf(enumClass, xmlValue);
}

public String objectToSQLString(Object value) {
    return '\'' + ( (Enum) value ).name() + '\'';
}

public String toXMLString(Object value) {
    return ( (Enum) value ).name();
}
}

枚舉類：

public enum TransmissionStatusType {
accepted,
rejected,
duplicate,
exception,
retry}

Answer 1

我想到了。 我需要在 nullSafeSet 函數中使用 setObject 而不是 setString 並傳入 Types.OTHER 作為 java.sql.type 讓 jdbc 知道它是一個 postgres 類型。

public void nullSafeSet(PreparedStatement st, Object value, int index) throws HibernateException, SQLException {
    if (value == null) {
        st.setNull(index, Types.VARCHAR);
    }
    else {
//            previously used setString, but this causes postgresql to bark about incompatible types.
//           now using setObject passing in the java type for the postgres enum object
//            st.setString(index,((Enum) value).name());
        st.setObject(index,((Enum) value), Types.OTHER);
    }
}

Answer 2

如果您在 PostgreSQL 中有以下post_status_info枚舉類型：

CREATE TYPE post_status_info AS ENUM (
    'PENDING', 
    'APPROVED', 
    'SPAM'
)

您可以使用以下自定義 Hibernate Type 輕松將 Java Enum 映射到 PostgreSQL Enum 列類型：

public class PostgreSQLEnumType extends org.hibernate.type.EnumType {
     
    public void nullSafeSet(
            PreparedStatement st, 
            Object value, 
            int index, 
            SharedSessionContractImplementor session) 
        throws HibernateException, SQLException {
        if(value == null) {
            st.setNull( index, Types.OTHER );
        }
        else {
            st.setObject( 
                index, 
                value.toString(), 
                Types.OTHER 
            );
        }
    }
}

要使用它，您需要使用 Hibernate @Type注釋來注釋該字段，如下例所示：

@Entity(name = "Post")
@Table(name = "post")
@TypeDef(
    name = "pgsql_enum",
    typeClass = PostgreSQLEnumType.class
)
public static class Post {
 
    @Id
    private Long id;
 
    private String title;
 
    @Enumerated(EnumType.STRING)
    @Column(columnDefinition = "post_status_info")
    @Type( type = "pgsql_enum" )
    private PostStatus status;
 
    //Getters and setters omitted for brevity
}

就是這樣，它就像一個魅力。 這是GitHub 上的一個測試，證明了這一點。

Answer 3

以下內容也可能有助於讓 Postgres 以靜默方式將字符串轉換為您的 SQL 枚舉類型，以便您可以使用@Enumerated(STRING)而不需要@Type 。

CREATE CAST (character varying as post_status_type) WITH INOUT AS IMPLICIT;

Answer 4

一個快速的解決方案是

jdbc:postgresql://localhost:5432/postgres?stringtype=unspecified

?stringtype=unspecified是答案

Answer 5

build.gradle.kts

dependencies {
    api("javax.persistence", "javax.persistence-api", "2.2")
    api("org.hibernate",  "hibernate-core",  "5.4.21.Final")
}

在 Kotlin 中，使用EnumType<Enum<*>>()進行通用擴展很重要

PostgreSQLEnumType.kt

import org.hibernate.type.EnumType
import java.sql.Types

class PostgreSQLEnumType : EnumType<Enum<*>>() {

    @Throws(HibernateException::class, SQLException::class)
    override fun nullSafeSet(
            st: PreparedStatement,
            value: Any,
            index: Int,
            session: SharedSessionContractImplementor) {
        st.setObject(
                index,
                value.toString(),
                Types.OTHER
        )
    }
}

定制.kt

import org.hibernate.annotations.Type
import org.hibernate.annotations.TypeDef
import javax.persistence.*

@Entity
@Table(name = "custom")
@TypeDef(name = "pgsql_enum", typeClass = PostgreSQLEnumType::class)
data class Custom(
        @Id @GeneratedValue @Column(name = "id")
        val id: Int,
    
        @Enumerated(EnumType.STRING) @Column(name = "status_custom") @Type(type = "pgsql_enum")
        val statusCustom: StatusCustom
)

enum class StatusCustom {
    FIRST, SECOND
}

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我不推薦的一個更簡單的選項是Arthur's answer 中的第一個選項，它在連接 URL 中向數據庫添加一個參數，以便枚舉數據類型不會丟失。 我認為在后端服務器和數據庫之間映射數據類型的責任正是后端。

<property name="connection.url">jdbc:postgresql://localhost:5432/yourdatabase?stringtype=unspecified</property>

來源

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