使用Odata服务的SAP UI5应用程序：object不是声明类的实例

Question

我创建了一个odata服务 http://localhost:8080/carandodatabaseodata/emplist.svc/ 当我访问上面的URL时，它会显示实体集。

<service xmlns="<LINK>2007/app" xmlns:atom="<LINK>2005/Atom" xml:base="<SAME URL AS ABOVE>carandodatabaseodata/emplist.svc/">
  <workspace>
    <atom:title>Default</atom:title>
    <collection href="ZaeScaleprinters">
        <atom:title>ZaeScaleprinters</atom:title>
    </collection>
  </workspace>
</service>

我也能正确查看元数据信息 以下网址工作正常。 carandodatabaseodata / emplist.svc / $元数据

<edmx:Edmx xmlns:edmx="http://schemas.microsoft.com/ado/2007/06/edmx" Version="1.0">
    <edmx:DataServices xmlns:m="http://schemas.microsoft.com/ado/2007/08/dataservices/metadata" m:DataServiceVersion="1.0">
        <Schema xmlns="http://schemas.microsoft.com/ado/2008/09/edm" Namespace="carandodatabaseodata">
            <EntityType Name="ZaeScaleprinter">
                <Key>
                    <PropertyRef Name="Printer" />
                    <PropertyRef Name="Scale" />
                    <PropertyRef Name="Werks" />
                </Key>
                <Property Name="Printer" Type="Edm.String" Nullable="false" MaxLength="120" />
                <Property Name="Scale" Type="Edm.String" Nullable="false" MaxLength="60" />
                <Property Name="Werks" Type="Edm.String" Nullable="false" MaxLength="12" />
            </EntityType>
            <EntityContainer Name="carandodatabaseodataContainer" m:IsDefaultEntityContainer="true">
                <EntitySet Name="ZaeScaleprinters" EntityType="carandodatabaseodata.ZaeScaleprinter" />
            </EntityContainer>
        </Schema>
    </edmx:DataServices>
</edmx:Edmx>

但是当我尝试使用时访问实际的实体集 carandodatabaseodata / emplist.svc / ZaeScaleprinters 它给我以下错误

<error xmlns="<LINK>/ado/2007/08/dataservices/metadata">
    <code/>
    <message xml:lang="en">
        "sun.reflect.NativeMethodAccessorImpl: object is not an instance of declaring class. "
    </message>
</error>

更新：我也粘贴了java代码。

package com;

import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;

import org.apache.olingo.odata2.processor.api.jpa.ODataJPAContext;
import org.apache.olingo.odata2.processor.api.jpa.ODataJPAServiceFactory;
import org.apache.olingo.odata2.processor.api.jpa.exception.ODataJPARuntimeException;

public class ZAE_SCALEPrinterServiceFactory extends ODataJPAServiceFactory {

    private static final String PERSISTENCE_UNIT_NAME = "carandodatabaseodata";

      @Override
      public ODataJPAContext initializeODataJPAContext()
          throws ODataJPARuntimeException {

        ODataJPAContext oDatJPAContext = this.getODataJPAContext();
        try {

          EntityManagerFactory emf = Persistence.createEntityManagerFactory(PERSISTENCE_UNIT_NAME);
    oDatJPAContext.setEntityManagerFactory(emf);
          oDatJPAContext.setPersistenceUnitName(PERSISTENCE_UNIT_NAME);

          return oDatJPAContext;

        } catch (Exception e) {

          throw new RuntimeException(e);

        }

      }

}

实体类：

package model;

import java.io.Serializable;
import javax.persistence.*;


/**
 * The persistent class for the ZAE_SCALEPRINTER database table.
 * 
 */
@Entity
@Table(name="ZAE_SCALEPRINTER")
public class ZaeScaleprinter implements Serializable {
    private static final long serialVersionUID = 1L;

    @EmbeddedId
    private ZaeScaleprinterPK id;

    public ZaeScaleprinter() {

    }

    public ZaeScaleprinterPK getId() {
        return this.id;
    }

    public void setId(ZaeScaleprinterPK id) {
        this.id = id;
    }

}

package model;

import java.io.Serializable;
import javax.persistence.*;

/**
 * The primary key class for the ZAE_SCALEPRINTER database table.
 * 
 */
@Embeddable
public class ZaeScaleprinterPK implements Serializable {
    //default serial version id, required for serializable classes.
    private static final long serialVersionUID = 1L;

    @Column(unique=true, nullable=false, length=12)
    private String werks;

    @Column(unique=true, nullable=false, length=60)
    private String scale;

    @Column(unique=true, nullable=false, length=120)
    private String printer;

    public ZaeScaleprinterPK() {
    }
    public String getWerks() {
        return this.werks;
    }
    public void setWerks(String werks) {
        this.werks = werks;
    }
    public String getScale() {
        return this.scale;
    }
    public void setScale(String scale) {
        this.scale = scale;
    }
    public String getPrinter() {
        return this.printer;
    }
    public void setPrinter(String printer) {
        this.printer = printer;
    }

    public boolean equals(Object other) {
        if (this == other) {
            return true;
        }
        if (!(other instanceof ZaeScaleprinterPK)) {
            return false;
        }
        ZaeScaleprinterPK castOther = (ZaeScaleprinterPK)other;
        return 
            this.werks.equals(castOther.werks)
            && this.scale.equals(castOther.scale)
            && this.printer.equals(castOther.printer);
    }

    public int hashCode() {
        final int prime = 31;
        int hash = 17;
        hash = hash * prime + this.werks.hashCode();
        hash = hash * prime + this.scale.hashCode();
        hash = hash * prime + this.printer.hashCode();

        return hash;
    }
}