如何使用HibernateMapPostgreSQL数组

w3nuxt5m  于 2022-11-14  发布在  PostgreSQL
关注(0)|答案(6)|浏览(115)

有人成功地将PostgreSQL中的数字数组Map到Java中的数字数组了吗？
SQL：

CREATE TABLE sal_emp (name text, pay_by_quarter integer[]);
INSERT INTO sal_emp VALUES ('one', '{1,2,3}');
INSERT INTO sal_emp VALUES ('two', '{4,5,6}');
INSERT INTO sal_emp VALUES ('three', '{2,4,6}');

Map：

<hibernate-mapping>
    <class name="SalEmp" table="sal_emp">
        <id name="name" />
        <property name="payByQuarter" column="pay_by_quarter" />
    </class>
</hibernate-mapping>

班级：

public class SalEmp implements Serializable{
    private String name;
    private Integer[] payByQuarter;
    ...// getters & setters
}

查询表时出现异常。

Hibernate

6条答案

按热度按时间
gz5pxeao

gz5pxeao1#

Maven依赖

您需要做的第一件事是在项目pom.xml配置文件中设置以下Hibernate Types Maven依赖项：

<dependency>
    <groupId>com.vladmihalcea</groupId>
    <artifactId>hibernate-types-52</artifactId>
    <version>${hibernate-types.version}</version>
</dependency>

假设您的数据库中有这个表：

create table event (
    id int8 not null, 
    version int4, 
    sensor_names text[], 
    sensor_values integer[], 
    primary key (id)
)

您想要这样Map它：

@Entity(name = "Event")
@Table(name = "event")
@TypeDefs({
    @TypeDef(
        name = "string-array", 
        typeClass = StringArrayType.class
    ),
    @TypeDef(
        name = "int-array", 
        typeClass = IntArrayType.class
    )
})
public static class Event extends BaseEntity {
 
    @Type( type = "string-array" )
    @Column(
        name = "sensor_names", 
        columnDefinition = "text[]"
    )
    private String[] sensorNames;
 
    @Type( type = "int-array" )
    @Column(
        name = "sensor_values", 
        columnDefinition = "integer[]"
    )
    private int[] sensorValues;
 
    //Getters and setters omitted for brevity
}

string-array和int-array是可以在BaseEntity超类中定义的自定义类型：

@TypeDefs({
    @TypeDef(
        name = "string-array", 
        typeClass = StringArrayType.class
    ),
    @TypeDef(
        name = "int-array", 
        typeClass = IntArrayType.class
    )
})
@MappedSuperclass
public class BaseEntity {

    @Id
    private Long id;

    @Version
    private Integer version;

    //Getters and setters omitted for brevity
}

StringArrayType和IntArrayType是由Hibernate Types项目提供的类。

测试时间

现在，当你插入几个实体时；

Event nullEvent = new Event();
nullEvent.setId(0L);
entityManager.persist(nullEvent);
 
Event event = new Event();
event.setId(1L);
event.setSensorNames(
    new String[] {
        "Temperature", 
        "Pressure"
    }
);
event.setSensorValues( 
    new int[] {
        12, 
        756
    } 
);
entityManager.persist(event);

Hibernate将生成以下SQL语句：

INSERT INTO event (
    version, 
    sensor_names, 
    sensor_values, 
    id
) 
VALUES (
    0, 
    NULL(ARRAY), 
    NULL(ARRAY), 
    0
)
     
INSERT INTO event (
    version, 
    sensor_names, 
    sensor_values, 
    id
) 
VALUES ( 
    0, 
    {"Temperature","Pressure"}, 
    {"12","756"}, 
    1
)
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gcmastyq

gcmastyq2#

Hibernate不支持开箱即用的数据库阵列(例如Map到java.sql.Array的阵列)。
Hibernate提供的array和primitive-array类型用于将Java数组Map到备份表-它们基本上是一对多/元素集合Map的变体，所以这不是您想要的。
不过，最新的PostgreSQL JDBC驱动程序(无论什么)都支持JDBC4 Connection.createArrayOf()方法以及ResultSet.getArray()和PreparedStatement.setArray()方法，因此您可以编写自己的UserType来提供数组支持。
Here是一个处理Oracle数组的UserType实现，它提供了一个很好的起点，改编它来处理java.sql.Array是相当简单的。

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57hvy0tb

57hvy0tb3#

也许这对其他人很有用：我发现在我的情况下，它的性能很差，不能与C3P0一起使用。(只是简单地探讨了这些问题，能不能解决，请指正！)
Hibernate 3.6：

import java.io.Serializable;
import java.sql.Array;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Arrays;

import org.apache.commons.lang.ArrayUtils;
import org.hibernate.HibernateException;
import org.hibernate.usertype.UserType;

public class IntArrayUserType implements UserType {
protected static final int  SQLTYPE = java.sql.Types.ARRAY;

@Override
public Object nullSafeGet(final ResultSet rs, final String[] names, final Object owner) throws HibernateException, SQLException {
    Array array = rs.getArray(names[0]);
    Integer[] javaArray = (Integer[]) array.getArray();
    return ArrayUtils.toPrimitive(javaArray);
}

@Override
public void nullSafeSet(final PreparedStatement statement, final Object object, final int i) throws HibernateException, SQLException {
    Connection connection = statement.getConnection();

    int[] castObject = (int[]) object;
    Integer[] integers = ArrayUtils.toObject(castObject);
    Array array = connection.createArrayOf("integer", integers);

    statement.setArray(i, array);
}

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

@Override
public Object deepCopy(final Object o) throws HibernateException {
    return o == null ? null : ((int[]) o).clone();
}

@Override
public Serializable disassemble(final Object o) throws HibernateException {
    return (Serializable) o;
}

@Override
public boolean equals(final Object x, final Object y) throws HibernateException {
    return x == null ? y == null : x.equals(y);
}

@Override
public int hashCode(final Object o) throws HibernateException {
    return o == null ? 0 : o.hashCode();
}

@Override
public boolean isMutable() {
    return false;
}

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

@Override
public Class<int[]> returnedClass() {
    return int[].class;
}

@Override
public int[] sqlTypes() {
    return new int[] { SQLTYPE };
}
}
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ds97pgxw

ds97pgxw4#

这已经针对字符串数组进行了测试。对于数字数组，可能需要对转换器进行一些修改。这可以与Spring JPA一起使用。
1)将PostgreSQLTextArray添加到您的项目

import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Arrays;
import java.util.Map;

/**
 * This is class provides {@link java.sql.Array} interface for PostgreSQL <code>text</code> array.
 *
 * @author Valentine Gogichashvili
 *
 */

public class PostgreSQLTextArray implements java.sql.Array {

    private final String[] stringArray;
    private final String stringValue;

    /**
     * Initializing constructor
     * @param stringArray
     */
    public PostgreSQLTextArray(String[] stringArray) {
        this.stringArray = stringArray;
        this.stringValue = stringArrayToPostgreSQLTextArray(this.stringArray);

    }

    @Override
    public String toString() {
        return stringValue;
    }

    private static final String NULL = "NULL";

    /**
     * This static method can be used to convert an string array to string representation of PostgreSQL text array.
     * @param a source String array
     * @return string representation of a given text array
     */
    public static String stringArrayToPostgreSQLTextArray(String[] stringArray) {
        final int arrayLength;
        if ( stringArray == null ) {
            return NULL;
        } else if ( ( arrayLength = stringArray.length ) == 0 ) {
            return "{}";
        }
        // count the string length and if need to quote
        int neededBufferLentgh = 2; // count the beginning '{' and the ending '}' brackets
        boolean[] shouldQuoteArray = new boolean[stringArray.length];
        for (int si = 0; si < arrayLength; si++) {
            // count the comma after the first element
            if ( si > 0 )  neededBufferLentgh++;

            boolean shouldQuote;
            final String s = stringArray[si];
            if ( s == null ) {
                neededBufferLentgh += 4;
                shouldQuote = false;
            } else {
                final int l = s.length();
                neededBufferLentgh += l;
                if ( l == 0 || s.equalsIgnoreCase(NULL) ) {
                    shouldQuote = true;
                } else {
                    shouldQuote = false;
                    // scan for commas and quotes
                    for (int i = 0; i < l; i++) {
                        final char ch = s.charAt(i);
                        switch(ch) {
                            case '"':
                            case '\\':
                                shouldQuote = true;
                                // we will escape these characters
                                neededBufferLentgh++;
                                break;
                            case ',':
                            case '\'':
                            case '{':
                            case '}':
                                shouldQuote = true;
                                break;
                            default:
                                if ( Character.isWhitespace(ch) ) {
                                    shouldQuote = true;
                                }
                                break;
                        }
                    }
                }
                // count the quotes
                if ( shouldQuote ) neededBufferLentgh += 2;
            }
            shouldQuoteArray[si] = shouldQuote;
        }

        // construct the String
        final StringBuilder sb = new StringBuilder(neededBufferLentgh);
        sb.append('{');
        for (int si = 0; si < arrayLength; si++) {
            final String s = stringArray[si];
            if ( si > 0 ) sb.append(',');
            if ( s == null ) {
                sb.append(NULL);
            } else {
                final boolean shouldQuote = shouldQuoteArray[si];
                if ( shouldQuote ) sb.append('"');
                for (int i = 0, l = s.length(); i < l; i++) {
                    final char ch = s.charAt(i);
                    if ( ch == '"' || ch == '\\' ) sb.append('\\');
                    sb.append(ch);
                }
                if ( shouldQuote ) sb.append('"');
            }
        }
        sb.append('}');
        assert sb.length() == neededBufferLentgh;
        return sb.toString();
    }

    @Override
    public Object getArray() throws SQLException {
        return stringArray == null ? null : Arrays.copyOf(stringArray, stringArray.length);
    }

    @Override
    public Object getArray(Map<String, Class<?>> map) throws SQLException {
        return getArray();
    }

    @Override
    public Object getArray(long index, int count) throws SQLException {
        return stringArray == null ? null : Arrays.copyOfRange(stringArray, (int) index, (int) index + count);
    }

    @Override
    public Object getArray(long index, int count, Map<String, Class<?>> map) throws SQLException {
        return getArray(index, count);
    }

    @Override
    public int getBaseType() throws SQLException {
        return java.sql.Types.VARCHAR;
    }

    @Override
    public String getBaseTypeName() throws SQLException {
        return "text";
    }

    @Override
    public ResultSet getResultSet() throws SQLException {
        throw new UnsupportedOperationException();
    }

    @Override
    public ResultSet getResultSet(Map<String, Class<?>> map) throws SQLException {
        throw new UnsupportedOperationException();
    }

    @Override
    public ResultSet getResultSet(long index, int count) throws SQLException {
        throw new UnsupportedOperationException();
    }

    @Override
    public ResultSet getResultSet(long index, int count, Map<String, Class<?>> map) throws SQLException {
        throw new UnsupportedOperationException();
    }

    @Override
    public void free() throws SQLException {
    }

}

2)将ListToArrayConverter添加到代码中

import org.postgresql.jdbc4.Jdbc4Array;

import javax.persistence.AttributeConverter;
import javax.persistence.Converter;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

@Converter(autoApply = true)
public class ListToArrayConveter implements AttributeConverter<List<String>, Object> {
    @Override
    public PostgreSQLTextArray convertToDatabaseColumn(List<String> attribute) {
        if (attribute == null || attribute.isEmpty()) {
            return null;
        }
        String[] rst = new String[attribute.size()];
        return new PostgreSQLTextArray(attribute.toArray(rst));
    }

    @Override
    public List<String> convertToEntityAttribute(Object dbData) {

        List<String> rst = new ArrayList<>();
        try {
            String[] elements = (String[]) ((Jdbc4Array) dbData).getArray();
            for (String element : elements) {
                rst.add(element);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }

        return rst;
    }
}

3)使用它！

@Entity
@Table(name = "emails")
public class Email {

    [...]

    @SuppressWarnings("JpaAttributeTypeInspection")
    @Column(name = "subject", columnDefinition = "text[]")
    @Convert(converter = ListToArrayConveter.class)
    private List<String> subject;

    [...]
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5kgi1eie

5kgi1eie5#

通过发布here的JPA Converter方法，我能够将String[]保存到PostgreSQL 9.4和NikpseLink 2.6.2
这似乎是答案的来源
2016年7月1日TK421号。
从数据库加载数组也很有效。
额外添加到persistence.xml我的ListToArrayConverter路径：

<class> com.foo1.foo2.foo3.backend.jpa.convert.ListToArrayConverter </class>

请注意，Postgre JDBC驱动程序中不再包含Jdbc4Array，请改用：

org.postgresql.jdbc.PgArray

查看此处：Package org.postgresql.jdbc4 is missing since 9.4-1207

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lokaqttq

lokaqttq6#

下面是我使用的int[] UserType，它还包括对nullSafeGet()和nullSafeSet()的NULL检查：

import org.apache.commons.lang.ArrayUtils;
import org.hibernate.HibernateException;
import org.hibernate.engine.spi.SessionImplementor;
import org.hibernate.usertype.UserType;

import java.io.Serializable;
import java.sql.Array;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

public class IntegerArrayUserType implements UserType {
    protected static final int  SQLTYPE = java.sql.Types.ARRAY;

    @Override
    public Object nullSafeGet(ResultSet rs, String[] names, SessionImplementor session, Object owner) throws HibernateException, SQLException {
        Array array = rs.getArray(names[0]);
        if (array == null) {
            return null;
        }
        Integer[] javaArray = (Integer[]) array.getArray();
        return ArrayUtils.toPrimitive(javaArray);
    }

    @Override
    public void nullSafeSet(PreparedStatement st, Object value, int index, SessionImplementor session) throws HibernateException, SQLException {
        Connection connection = st.getConnection();

        if (value == null) {
            st.setNull( index, sqlTypes()[0] );
        } else {
            int[] castObject = (int[]) value;
            Integer[] integers = ArrayUtils.toObject(castObject);
            Array array = connection.createArrayOf("integer", integers);

            st.setArray(index, array);
        }
    }

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

    @Override
    public Object deepCopy(final Object o) throws HibernateException {
        return o == null ? null : ((int[]) o).clone();
    }

    @Override
    public Serializable disassemble(final Object o) throws HibernateException {
        return (Serializable) o;
    }

    @Override
    public boolean equals(final Object x, final Object y) throws HibernateException {
        return x == null ? y == null : x.equals(y);
    }

    @Override
    public int hashCode(final Object o) throws HibernateException {
        return o == null ? 0 : o.hashCode();
    }

    @Override
    public boolean isMutable() {
        return false;
    }

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

    @Override
    public Class<int[]> returnedClass() {
        return int[].class;
    }

    @Override
    public int[] sqlTypes() {
        return new int[] { SQLTYPE };
    }
}
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