创建PostgreSQL数组类型，如；文本[]”；使用JPA（EclipseLink）

我很难创建一个JPA模型类，EclipseLink将从中创建 以下是PostgreSQL DDL：

CREATE TABLE array_example (
  id serial not null, 
  params text[] not null
);

据我所知，PostgreSQL的数组类型不是SQL标准，因此不包含在JPA标准中。EclipseLink似乎对非标准扩展有某种支持。到目前为止，我得出了以下结论：

....
import org.eclipse.persistence.annotations.Array;
import org.eclipse.persistence.annotations.Struct;

@Entity
@Table(name = "array_example")
@Struct(name = "params") // Else: [EclipseLink-157] "Normal descriptors do not support non-relational extensions."
@XmlRootElement
public class ArrayExamplePostgres implements Serializable {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Basic(optional = false)
    @Column(name = "id")
    private int id;

    @NotNull
    @Array(databaseType = "TEXT[]") // Needs @Struct on class!
    @Column(name = "params")
    private List<String> params;
    ....

PostgreSQL日志文件包含两个可疑的SELECT（返回1009 for _text，然后返回typedelim=NULL），在由于缺少表而失败之前不久：

2014-05-12 01:34:32 CEST postgres@java_test_ee6_jpa [17555] LOG:  execute <unnamed>: SELECT oid FROM pg_catalog.pg_type WHERE typname = $1
2014-05-12 01:34:32 CEST postgres@java_test_ee6_jpa [17555] DETAIL:  parameters: $1 = '_text

2014-05-12 01:34:32 CEST postgres@java_test_ee6_jpa [17555] LOG:  execute <unnamed>: SELECT e.typdelim FROM pg_catalog.pg_type t, pg_catalog.pg_type e WHERE t.oid = $1 and t.typelem = e.oid
2014-05-12 01:34:32 CEST postgres@java_test_ee6_jpa [17555] DETAIL:  parameters: $1 = '1009'

2014-05-12 01:34:32 CEST postgres@java_test_ee6_jpa [17555] LOG:  execute S_1: BEGIN
2014-05-12 01:34:32 CEST postgres@java_test_ee6_jpa [17555] ERROR:  relation "array_example" does not exist at character 13
2014-05-12 01:34:32 CEST postgres@java_test_ee6_jpa [17555] STATEMENT:  INSERT INTO array_example (params) VALUES ($1)

---

也许此示例项目有帮助：

---

我在一个删除的答案中建议，它似乎在寻找

text[]

的数组类型，即文本数组的数组，这是不受支持的，所以你应该尝试一下

text

。这似乎解决了眼前的问题，但根据上面的编辑创建了不同的ORM。恐怕很多Java ORM除了关系数据库最基本的最低公分母特性外，什么都不擅长。在本例中，我认为它试图生成字段，就好像它是EclipseLink“NoSQL”支持的非关系对象一样。最后一个查询确实为文本类型的内置数组找到了正确的oid（1009）。警告指出，只有关系数据库类才支持模式生成。一旦添加了结构或数组扩展类型，就不能使用模式生成，因为对所有各种DB类型的支持都不存在，而且实际上，所有这些类型都是可用的—这些类型用于遗留系统上的自定义数据库类型。在大多数情况下，最好使用现有的可移植类型，或者使用脚本创建数据库。

2014-05-12 01:34:32 CEST postgres@java_test_ee6_jpa [17555] LOG:  execute <unnamed>: SELECT oid FROM pg_catalog.pg_type WHERE typname = $1
2014-05-12 01:34:32 CEST postgres@java_test_ee6_jpa [17555] DETAIL:  parameters: $1 = '_text

2014-05-12 01:34:32 CEST postgres@java_test_ee6_jpa [17555] LOG:  execute <unnamed>: SELECT e.typdelim FROM pg_catalog.pg_type t, pg_catalog.pg_type e WHERE t.oid = $1 and t.typelem = e.oid
2014-05-12 01:34:32 CEST postgres@java_test_ee6_jpa [17555] DETAIL:  parameters: $1 = '1009'

2014-05-12 01:34:32 CEST postgres@java_test_ee6_jpa [17555] LOG:  execute S_1: BEGIN
2014-05-12 01:34:32 CEST postgres@java_test_ee6_jpa [17555] ERROR:  relation "array_example" does not exist at character 13
2014-05-12 01:34:32 CEST postgres@java_test_ee6_jpa [17555] STATEMENT:  INSERT INTO array_example (params) VALUES ($1)

<persistence-unit name="postgresJavaTestJpaPU" transaction-type="RESOURCE_LOCAL">
    <provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
    <class>de.lathspell.java_test_ee6_jpa.model.ArrayExamplePostgres</class>
    ...
    <exclude-unlisted-classes>true</exclude-unlisted-classes>
    <properties>
        <property name="javax.persistence.jdbc.driver" value="org.postgresql.Driver"/>
        <property name="javax.persistence.jdbc.url" value="jdbc:postgresql:java_test_ee6_jpa"/>
        <property name="javax.persistence.jdbc.user" value="postgres"/>
        <property name="javax.persistence.jdbc.password" value="secret"/>
        <property name="eclipselink.ddl-generation.output-mode" value="both"/>
        <property name="eclipselink.ddl-generation" value="drop-and-create-tables"/>
        <property name="eclipselink.drop-ddl-jdbc-file-name" value="src/main/sql/eclipselink-postgres-drop.sql"/>
        <property name="eclipselink.create-ddl-jdbc-file-name" value="src/main/sql/eclipselink-postgres-create.sql"/>
        <property name="eclipselink.jdbc.native-sql" value="true"/>
    </properties>
</persistence-unit>

2014-05-12 23:03:08 CEST postgres@java_test_ee7_jpa [4183] LOG:  execute <unnamed>: SELECT pg_type.oid   FROM pg_catalog.pg_type   LEFT   JOIN (select ns.oid as nspoid, ns.nspname, r.r           from pg_namespace as ns           join ( select s.r, (current_schemas(false))[s.r] as nspname                    from generate_series(1, array_upper(current_schemas(false), 1)) as s(r) ) as r          using ( nspname )        ) as sp     ON sp.nspoid = typnamespace  WHERE typname = $1  ORDER BY sp.r, pg_type.oid DESC LIMIT 1
2014-05-12 23:03:08 CEST postgres@java_test_ee7_jpa [4183] DETAIL:  parameters: $1 = '_TEXT'
-> 0 rows

2014-05-12 23:12:21 CEST postgres@java_test_ee7_jpa [4435] LOG:  execute <unnamed>: SELECT pg_type.oid   FROM pg_catalog.pg_type   LEFT   JOIN (select ns.oid as nspoid, ns.nspname, r.r           from pg_namespace as ns           join ( select s.r, (current_schemas(false))[s.r] as nspname                    from generate_series(1, array_upper(current_schemas(false), 1)) as s(r) ) as r          using ( nspname )        ) as sp     ON sp.nspoid = typnamespace  WHERE typname = $1  ORDER BY sp.r, pg_type.oid DESC LIMIT 1
2014-05-12 23:12:21 CEST postgres@java_test_ee7_jpa [4435] DETAIL:  parameters: $1 = '_text[]'
-> 0 rows

2014-05-12 23:04:46 CEST postgres@java_test_ee7_jpa [4266] LOG:  execute <unnamed>: SELECT pg_type.oid   FROM pg_catalog.pg_type   LEFT   JOIN (select ns.oid as nspoid, ns.nspname, r.r           from pg_namespace as ns           join ( select s.r, (current_schemas(false))[s.r] as nspname                    from generate_series(1, array_upper(current_schemas(false), 1)) as s(r) ) as r          using ( nspname )        ) as sp     ON sp.nspoid = typnamespace  WHERE typname = $1  ORDER BY sp.r, pg_type.oid DESC LIMIT 1
2014-05-12 23:04:46 CEST postgres@java_test_ee7_jpa [4266] DETAIL:  parameters: $1 = '_text'
--> 1009
2014-05-12 23:04:46 CEST postgres@java_test_ee7_jpa [4266] LOG:  execute <unnamed>: SELECT e.typdelim FROM pg_catalog.pg_type t, pg_catalog.pg_type e WHERE t.oid = $1 and t.typelem = e.oid
2014-05-12 23:04:46 CEST postgres@java_test_ee7_jpa [4266] DETAIL:  parameters: $1 = '1009'
--> ','

org.eclipse.persistence.default
WARNING: The default table generator currently only supports generating default table schema from a relational project.