How WSO2DSS manage the XML mapping of queries which contains some columns with null value

https://stackoverflow.com/questions/9774736

25-05-2021
|

Question

I have a simple query

select t.firstname, t.lastname, t.zipcode, t.city 
from name_data t where name_id = ?

The '?' is the input parameter and is never null.

The query returns a record looking like one of these:

Case 1 - Individual

 'First Name'   'Last Name'     'zipcode'   'city'
 -------------------------------------------------------
 John           Doe             1177        Somewhere

Case 2 - Company

 'First Name'   'Last Name'     'zipcode'   'city'
 -----------------------------------------------------------
 <<null>>       ACME Ltd        1199        'Somewhere else'

When I am getting the second record, The DSS throw a NullPointerException.

I guess this is because the <> value in Firstname and I found a way to bypass this by testing the null value in the SQL (Oracle)

"select nvl(t.firstname, ' ') firstname, nvl(t.lastname, ' '), lastname, nvl(t.zipcode, ' '), nvl(t.city, ' ') etc..."

And this for all columns which can be null (my query is a bit longer than this) as they are optionnal.

I know this should not happens (in theory) if the database was correctly designed (like create two different entities for managing people and companies) but it is a commercial product and then I just cannot change it and I took a simple case to explain instead a long query.

The extract of my .dbs is:

<?xml version="1.0" encoding="UTF-8"?>
<data xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xsi:noNamespaceSchemaLocation="http:///org/wso2/carbonstudio/eclipse/ds" 
    name="${groupId}.${artifactId}-customeraddress-1" 
    serviceNamespace="urn:customeraddress.database.mycompany.org/1" 
    serviceGroup="${groupId}" baseURI="">
  <description>This is the datasource to access the customer address information</description>
  <config id="ambocs">
    <property name="org.wso2.ws.dataservice.driver">@ambocs.driver@</property>
    <property name="org.wso2.ws.dataservice.protocol">@ambocs.url@</property>
    <property name="org.wso2.ws.dataservice.user">@ambocs.user@</property>
    <property name="org.wso2.ws.dataservice.password">@ambocs.password@</property>
    <property name="org.wso2.ws.dataservice.minpoolsize">@ambocs.minpoolsize@</property>
    <property name="org.wso2.ws.dataservice.maxpoolsize">@ambocs.maxpoolsize@</property>
    <property name="org.wso2.ws.dataservice.validation_query">select 1 from dual</property>
  </config>
  <query id="getCustomerAddressByIdRef" useConfig="ambocs" returnRowId="true">
    <sql>
        select 
            nvl(nd.first_name, ' ') first_name, 
            nvl(nd.last_name, ' ') last_name,
            nvl(nd.adr_zip, ' ') zipcode,
            nvl(nd.adr_city, ' ') city, 
            nvl(nd.adr_country, ' ') country 
        from name_data nd
        where nd.name_id = ?
    </sql>
    <properties>
      <property name="org.wso2.ws.dataservice.query_timeout"></property>
      <property name="org.wso2.ws.dataservice.fetch_direction"></property>
      <property name="org.wso2.ws.dataservice.fetch_size"></property>
      <property name="org.wso2.ws.dataservice.max_field_size"></property>
      <property name="org.wso2.ws.dataservice.max_rows"></property>
    </properties>
    <result element="ContactDetails" rowName="ContactDetail" 
       defaultNamespace="urn:customeraddress.database.mycompany.org/1" outputType="xml">
      <attribute name="firstName" column="first_name" query-param="" requiredRoles="" xsdType="xs:string"/>
      <attribute name="lastName" column="last_business_name" query-param="" requiredRoles="" xsdType="xs:string"/>
      <attribute name="locality" column="city" query-param="" requiredRoles="" xsdType="xs:string"/>
      <attribute name="postcode" column="zipcode" query-param="" requiredRoles="" xsdType="xs:string"/>
      <attribute name="country" column="country" query-param="" requiredRoles="" xsdType="xs:string"/>      
    </result>
    <param name="nameId" type="IN" sqlType="STRING" defaultValue="" />
  </query>
  <operation name="getCustomerAddressById">
    <call-query href="getCustomerAddressByIdRef">
        <with-param name="nameId" column="nameId" query-param="nameId"/>
    </call-query>
  </operation>
</data>

Do you know if there is an option to put in the .dbs in order to manage the null value returned by the query?

I tried to find a documentation on the wso2.org but it is very simple examples and nothing about this case.

UPDATE Here the table schema:

CREATE TABLE "NAME_DATA"
(
    "NAME_ID"               NUMBER(9,0) CONSTRAINT "PK_NAME_ID" NOT NULL ENABLE,
    "SYS_CREATION_DATE"     DATE NOT NULL ENABLE,
    "SYS_UPDATE_DATE"       DATE,
    "LAST_NAME"             VARCHAR2(60),
    "FIRST_NAME"            VARCHAR2(32),
    "ZIP_CODE"              VARCHAR2(4),
    "CITY"                  VARCHAR2(255),
    "COUNTRY"               CHAR(3 BYTE),
    CONSTRAINT "NAME_DATA_PK" PRIMARY KEY ("NAME_ID")
) 

CREATE UNIQUE INDEX "NAME_DATA_PK" ON "NAME_DATA" ("NAME_ID")
CREATE INDEX "IDX_NAME_DATA_1" ON "NAME_DATA"("LAST_NAME","FIRST_NAME")
CREATE INDEX "IDX_NAME_DATA_2" ON "NAME_DATA"(UPPER("FIRST_NAME"))
CREATE INDEX "IDX_NAME_DATA_3" ON "NAME_DATA"(UPPER("LAST_NAME"))

UPDATE 2 - stacktrace:

TID: [0] [WSO2 Data Services Server] [2012-03-27 14:02:22,730] ERROR {org.apache.axis2.transport.http.AxisServlet} -   {org.apache.axis2.transport.http.AxisServlet}
java.lang.NullPointerException
    at com.ctc.wstx.sw.BaseNsStreamWriter.doWriteAttr(BaseNsStreamWriter.java:468)
    at com.ctc.wstx.sw.BaseNsStreamWriter.writeAttribute(BaseNsStreamWriter.java:230)
    at org.apache.axiom.util.stax.wrapper.XMLStreamWriterWrapper.writeAttribute(XMLStreamWriterWrapper.java:88)
    at org.apache.axiom.om.impl.MTOMXMLStreamWriter.writeAttribute(MTOMXMLStreamWriter.java:230)
    at org.wso2.carbon.dataservices.core.engine.DSWrappedXMLStreamWriter.writeXMLEvent(DSWrappedXMLStreamWriter.java:418)
    at org.wso2.carbon.dataservices.core.engine.DSWrappedXMLStreamWriter.writeOutInitialXMLEvents(DSWrappedXMLStreamWriter.java:508)
    at org.wso2.carbon.dataservices.core.engine.DSWrappedXMLStreamWriter.finalizeBuffering(DSWrappedXMLStreamWriter.java:501)
    at org.wso2.carbon.dataservices.core.engine.DSWrappedXMLStreamWriter.flush(DSWrappedXMLStreamWriter.java:145)
    at org.wso2.carbon.dataservices.core.engine.DSOMDataSource.execute(DSOMDataSource.java:102)
    at org.wso2.carbon.dataservices.core.engine.DSOMDataSource.serialize(DSOMDataSource.java:110)
    at org.apache.axiom.om.impl.llom.OMSourcedElementImpl.internalSerialize(OMSourcedElementImpl.java:691)
    at org.apache.axiom.om.impl.util.OMSerializerUtil.serializeChildren(OMSerializerUtil.java:563)
    at org.apache.axiom.om.impl.llom.OMElementImpl.internalSerialize(OMElementImpl.java:875)
    at org.apache.axiom.soap.impl.llom.SOAPEnvelopeImpl.serializeInternally(SOAPEnvelopeImpl.java:283)
    at org.apache.axiom.soap.impl.llom.SOAPEnvelopeImpl.internalSerialize(SOAPEnvelopeImpl.java:245)
    at org.apache.axiom.om.impl.llom.OMSerializableImpl.serializeAndConsume(OMSerializableImpl.java:193)
    at org.apache.axis2.transport.http.SOAPMessageFormatter.writeTo(SOAPMessageFormatter.java:74)
    at org.apache.axis2.transport.http.CommonsHTTPTransportSender.sendUsingOutputStream(CommonsHTTPTransportSender.java:409)
    at org.apache.axis2.transport.http.CommonsHTTPTransportSender.invoke(CommonsHTTPTransportSender.java:286)
    at org.apache.axis2.engine.AxisEngine.send(AxisEngine.java:443)
    at org.apache.axis2.receivers.AbstractInOutSyncMessageReceiver.invokeBusinessLogic(AbstractInOutSyncMessageReceiver.java:45)
    at org.apache.axis2.receivers.AbstractMessageReceiver.receive(AbstractMessageReceiver.java:110)
    at org.apache.axis2.engine.AxisEngine.receive(AxisEngine.java:181)
    at org.apache.axis2.transport.http.HTTPTransportUtils.processHTTPPostRequest(HTTPTransportUtils.java:172)
    at org.apache.axis2.transport.http.AxisServlet.doPost(AxisServlet.java:146)
    at org.wso2.carbon.core.transports.CarbonServlet.doPost(CarbonServlet.java:199)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:641)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
    at org.eclipse.equinox.http.servlet.internal.ServletRegistration.handleRequest(ServletRegistration.java:90)
    at org.eclipse.equinox.http.servlet.internal.ProxyServlet.processAlias(ProxyServlet.java:111)
    at org.eclipse.equinox.http.servlet.internal.ProxyServlet.service(ProxyServlet.java:67)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
    at org.wso2.carbon.bridge.BridgeServlet.service(BridgeServlet.java:164)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:304)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:240)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:164)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:462)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:164)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)
    at org.wso2.carbon.server.CarbonStuckThreadDetectionValve.invoke(CarbonStuckThreadDetectionValve.java:154)
    at org.wso2.carbon.server.TomcatServer$1.invoke(TomcatServer.java:254)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:563)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:399)
    at org.apache.coyote.http11.Http11NioProcessor.process(Http11NioProcessor.java:396)
    at org.apache.coyote.http11.Http11NioProtocol$Http11ConnectionHandler.process(Http11NioProtocol.java:356)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1534)
    at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
    at java.lang.Thread.run(Thread.java:662)
TID: [0] [WSO2 Data Services Server] [2012-03-27 14:02:22,730] ERROR {org.apache.axis2.transport.http.AxisServlet} -   {org.apache.axis2.transport.http.AxisServlet}
java.lang.NullPointerException
    at com.ctc.wstx.sw.BaseNsStreamWriter.doWriteAttr(BaseNsStreamWriter.java:468)
    at com.ctc.wstx.sw.BaseNsStreamWriter.writeAttribute(BaseNsStreamWriter.java:230)
    at org.apache.axiom.util.stax.wrapper.XMLStreamWriterWrapper.writeAttribute(XMLStreamWriterWrapper.java:88)
    at org.apache.axiom.om.impl.MTOMXMLStreamWriter.writeAttribute(MTOMXMLStreamWriter.java:230)
    at org.wso2.carbon.dataservices.core.engine.DSWrappedXMLStreamWriter.writeXMLEvent(DSWrappedXMLStreamWriter.java:418)
    at org.wso2.carbon.dataservices.core.engine.DSWrappedXMLStreamWriter.writeOutInitialXMLEvents(DSWrappedXMLStreamWriter.java:508)
    at org.wso2.carbon.dataservices.core.engine.DSWrappedXMLStreamWriter.finalizeBuffering(DSWrappedXMLStreamWriter.java:501)
    at org.wso2.carbon.dataservices.core.engine.DSWrappedXMLStreamWriter.flush(DSWrappedXMLStreamWriter.java:145)
    at org.wso2.carbon.dataservices.core.engine.DSOMDataSource.execute(DSOMDataSource.java:102)
    at org.wso2.carbon.dataservices.core.engine.DSOMDataSource.serialize(DSOMDataSource.java:110)
    at org.apache.axiom.om.impl.llom.OMSourcedElementImpl.internalSerialize(OMSourcedElementImpl.java:691)
    at org.apache.axiom.om.impl.util.OMSerializerUtil.serializeChildren(OMSerializerUtil.java:563)
    at org.apache.axiom.om.impl.llom.OMElementImpl.internalSerialize(OMElementImpl.java:875)
    at org.apache.axiom.soap.impl.llom.SOAPEnvelopeImpl.serializeInternally(SOAPEnvelopeImpl.java:283)
    at org.apache.axiom.soap.impl.llom.SOAPEnvelopeImpl.internalSerialize(SOAPEnvelopeImpl.java:245)
    at org.apache.axiom.om.impl.llom.OMSerializableImpl.serializeAndConsume(OMSerializableImpl.java:193)
    at org.apache.axis2.transport.http.SOAPMessageFormatter.writeTo(SOAPMessageFormatter.java:74)
    at org.apache.axis2.transport.http.CommonsHTTPTransportSender.sendUsingOutputStream(CommonsHTTPTransportSender.java:409)
    at org.apache.axis2.transport.http.CommonsHTTPTransportSender.invoke(CommonsHTTPTransportSender.java:286)
    at org.apache.axis2.engine.AxisEngine.send(AxisEngine.java:443)
    at org.apache.axis2.receivers.AbstractInOutSyncMessageReceiver.invokeBusinessLogic(AbstractInOutSyncMessageReceiver.java:45)
    at org.apache.axis2.receivers.AbstractMessageReceiver.receive(AbstractMessageReceiver.java:110)
    at org.apache.axis2.engine.AxisEngine.receive(AxisEngine.java:181)
    at org.apache.axis2.transport.http.HTTPTransportUtils.processHTTPPostRequest(HTTPTransportUtils.java:172)
    at org.apache.axis2.transport.http.AxisServlet.doPost(AxisServlet.java:146)
    at org.wso2.carbon.core.transports.CarbonServlet.doPost(CarbonServlet.java:199)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:641)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
    at org.eclipse.equinox.http.servlet.internal.ServletRegistration.handleRequest(ServletRegistration.java:90)
    at org.eclipse.equinox.http.servlet.internal.ProxyServlet.processAlias(ProxyServlet.java:111)
    at org.eclipse.equinox.http.servlet.internal.ProxyServlet.service(ProxyServlet.java:67)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
    at org.wso2.carbon.bridge.BridgeServlet.service(BridgeServlet.java:164)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:304)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:240)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:164)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:462)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:164)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)
    at org.wso2.carbon.server.CarbonStuckThreadDetectionValve.invoke(CarbonStuckThreadDetectionValve.java:154)
    at org.wso2.carbon.server.TomcatServer$1.invoke(TomcatServer.java:254)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:563)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:399)
    at org.apache.coyote.http11.Http11NioProcessor.process(Http11NioProcessor.java:396)
    at org.apache.coyote.http11.Http11NioProtocol$Http11ConnectionHandler.process(Http11NioProtocol.java:356)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1534)
    at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
    at java.lang.Thread.run(Thread.java:662)

For testing this, you have to remove all "nvl(...)" in the DBS otherwise it is working well. It was a record where the first_name was "null".

Solution

This issue occurs when you use "attribute" type output-mappings in your result set. Here is the Jira created for it.

As a workaround, you can use columns as elements rather than as attributes, it can deal with null values properly.

i.e in above provided dbs file, use the result set as follows.

<result element="ContactDetails" rowName="ContactDetail" 
   defaultNamespace="urn:customeraddress.database.mycompany.org/1" outputType="xml">
  <element name="firstName" column="first_name" query-param="" requiredRoles="" xsdType="xs:string"/>
  <element name="lastName" column="last_business_name" query-param="" requiredRoles="" xsdType="xs:string"/>
  <element name="locality" column="city" query-param="" requiredRoles="" xsdType="xs:string"/>
  <element name="postcode" column="zipcode" query-param="" requiredRoles="" xsdType="xs:string"/>
  <element name="country" column="country" query-param="" requiredRoles="" xsdType="xs:string"/>      
</result>

OTHER TIPS

Could you mention the data-service version that you are using? This works fine in the latests packs (wso2dataservices-2.6.3). If you have 'null' values in database table then it will show you as "xsi:nil="true"" in the result you retrieve through dss.

Following result shows you an example for this where last result set contains a null values in table.

<Entries xmlns="http://ws.wso2.org/dataservice">
   <Entry>
      <EMPLOYEENUMBER>1</EMPLOYEENUMBER>
      <LASTNAME>dinusha</LASTNAME>
   </Entry>
   <Entry>
      <EMPLOYEENUMBER **xsi:nil="true"** xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"/>
      <LASTNAME **xsi:nil="true**" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"/>
   </Entry>
</Entries>

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