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Written by: Andy Zeneski, jaz@ofbizjaz@apache.org
Edited by: Les Austin

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Related Documents:

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relatedDocuments relatedDocuments

• Service Engine Configuration Guide
• XML File Definitions

Introduction

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introduction introduction

The Services Framework is new to OFBiz in Version 2. Services are defined as independent pieces of logic which when placed together can be used to process many different types of business requirements. Services can be of many different types: Workflow, Rules, Java, SOAP, BeanShellGroovy, etc. A service with the type Java is much like an event where it is a static method, however with the Services Framework we do not limit to web based applications. Services require input parameters to be in a Map and the results are returned in a Map as well. This is nice since a Map can be serialized and stored or passed via HTTP (SOAP).

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Services have the ability to call other services. So, chaining small services together to accomplish a larger task makes reusing existing services much easier.

Services which are used in different applications can be defined only once by creating Global Service Definition files or services specific to an application can be restricted and available only to that application.

When used in a web application services are available to web events, which allow events to stay small and reuse existing logic in the Services Framework. Also, services can be defined as 'exportable' which means they are allowed to be accessed by outside parties. Currently there is a SOAP EventHandler which allows services to be made available via SOAP. Other forms of remote invocation may be added to the framework in the future.

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declared in a component (service-resource in ofbiz-component.xml file) are reachable from anywhere in OFBiz, and even outside using the export feature. Though this possibility is not commonly used (no examples OOTB), it's also possible to create services which are specific to an application: restricted to be available only in that application. For that, you put the service definition and implementation files under the WEB-INF directory. You can also override a service by using the same name down in the deployment context (which is first framework, then themes, then applications, then specialpurpose, then hot-deploy). This is handy, but beware if not wanted...

When used in a web application services are available to web events, which allow events to stay small and reuse existing logic in the Services Framework. Also, services can be defined as 'exportable' which means they are allowed to be accessed by outside parties. Currently there is a SOAP EventHandler which allows services to be made available via SOAP. Other forms of remote invocation may be added to the framework in the future.

Service Dispatcher

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serviceDispatcher serviceDispatcher

The Service Dispatcher handles dispatching services to the appropriate Service Engine where it is then invoked. There is exactly one ServiceDispatcher for each Entity Delegator. If there are multiple delegators in an application there will also be multiple dispatchers. The ServiceDispatcher is accessed via a LocalDispatcher. There can be many LocalDispatchers associated with a ServiceDispatcher. Each LocalDispatcher is uniquely named and contains its own list of service definitions. When creating an instance of a LocalDispatcher, a DispatchContext is also created and passed to the ServiceEngine.

A LocalDispatcher is associated with an application. Applications never talk directly to the ServiceDispatcher. The LocalDispatcher contains an API for invoking services, which are routed through the ServiceDispather. However, applications may be running in different threads than the actual ServiceDispatcher, so it is left to the LocalDispatcher to keep a DispatchContext which among other things keeps a reference to the applications classloader.

Dispatch Context

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dispatchContext dispatchContext

The DispatchContext is created by the LocalDispatcher upon instantiation. This is the runtime dispatcher context. It contains necessary information to process services for each dispatcher. This context contains the reference to each of the service definition files, the classloader which should be used for invocation, a reference to the delegator and its dispatcher along with a 'bag' of user defined attributes. This context is passed on to each service when invoked and is used by the dispatcher to determine the service's model.

Service Engine

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serviceEngine serviceEngine

This is where the service is actually invoked. Each service has an engine name assigned in its definition. This engine name is mapped via the serviceengine.xml file and is instantiated by the GenericEngineFactory when called upon. Third-party engines are supported and must follow the GenericEngine interface when implemented.

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The Service Dispatcher handles dispatching services to the appropriate Service Engine where it is then invoked. There is exactly one ServiceDispatcher for each Entity Delegator. If there are multiple delegators in an application there will also be multiple dispatchers. The ServiceDispatcher is accessed via a LocalDispatcher. There can be many LocalDispatchers associated with a ServiceDispatcher. Each LocalDispatcher is uniquely named and contains its own list of service definitions. When creating an instance of a LocalDispatcher, a DispatchContextis also created and passed to the ServiceEngine.

A LocalDispatcher is associated with an application. Applications never talk directly to the ServiceDispatcher. The LocalDispatcher contains an API for invoking services, which are routed through the ServiceDispather. However, applications may be running in different threads than the actual ServiceDispatcher, so it is left to the LocalDispatcher to keep a DispatchContext which among other things keeps a reference to the applications classloader.

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The DispatchContext is created by the LocalDispatcher upon instantiation. This is the runtime dispatcher context. It contains necessary information to process services for each dispatcher. This context contains the reference to each of the service definition files, the classloader which should be used for invocation, a reference to the delegator and its dispatcher along with a 'bag' of user defined attributes. This context is passed on to each service when invoked and is used by the dispatcher to determine the service's model.

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This is where the service is actually invoked. Each service has an engine name assigned in its definition. This engine name is mapped via the serviceengine.xml file and is instantiated by the GenericEngineFactory when called upon. Third-party engines are supported and must follow the GenericEngine interface when implemented. See the Service Engine Configuration Guide for details on defining engines.

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Services are defined with a unique name, associated to a specific service engine and the input and output parameters are defined explicitly. Below is an example of a service definition:

<service name="userLogin" engine="java" location="org.ofbiz.commonapp.security.login.LoginServices" invoke="userLogin">
    <description>Authenticate a username/password; create a UserLogin object</description>
    <attribute name="login.username" type="String" mode="IN"/>
    <attribute name="login.password" type="String" mode="IN"/>
    <attribute name="userLogin" type="org.ofbiz.entity.GenericValue" mode="OUT" optional="true"/>
</service>

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Above you can see the name of this service is userLogin and it uses the java engine. This service expects two required IN parameters: login.username and login.password. Required parameters are tested before the service is invoked. If the parameters does not match by name and object type the service is not invoked. Parameters which may or may not be sent to the service should be defined as optional. After the service is invoked, the OUT parameters are tested. Only required parameters are tested, however if a parameter is passed which is not defined as optional or required it will cause the service to fail. This service has not required OUT parameters, so the result is simply returnedit will cause the service to fail. This service has not required OUT parameters, so the result is simply returned.

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Automatic Entity Maintenance Service Definition

OFBiz can automatically define services for simple Create, Update and Delete (CrUD) operations for many entities.

Set the engine attribute to "entity-auto" and the invoke attribute to "create", "update", or "delete". 

For example:

<service name="createInvoiceContactMech" engine="entity-auto" invoke="create" default-entity-name="InvoiceContactMech">
    <description>Create a ContactMech for an invoice</description>
    <permission-service service-name="acctgInvoicePermissionCheck" main-action="CREATE"/>
    <auto-attributes include="pk" mode="IN" optional="false"/>
</service>

The entity-auto engine can implement the following Create operations:

1. a single OUT primary key for primary auto-sequencing
2. a single INOUT primary key for primary auto-sequencing with optional override
3. a multi-part primary key with all parts part IN except the last which is OUT only (the missing primary key is a sub-sequence mainly for entity association
4. all primary key fields IN for a manually specified primary key

For any more complex situation, write code for your own service instead of relying on an automatically defined one.

Usage

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Internal Usage of the Services Framework is quite simple. In a Web Application the LocalDispatcher is stored in the ServletContext which can be accessed via the Session object in an Event. For non-web based applications you simply create a GenericDispatcher: GenericDelegator delegator = GenericDelegator.getGenericDelegator("default");
LocalDispatcher dispatcher = new GenericDispatcher("UniqueName",delegator);
Now we have a dispatcher which we can use to invoke services. To invoke the test service create a Map for the context which contains the IN parameter message *then invoke the service:*

Map context = UtilMisc.toMap("message","This is a test.");
Map result = null;

try {
    result = dispatcher.runSync("testScv", context);
} catch (GenericServiceException e) {
    e.printStackTrace();
}

if (result != null) {
    System.out.println("Result from service: " + (String) result.get("resp"));
}

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To schedule a service to run at a later time or to repeat use this:

// This example will schedule a job to run now.
Map context = UtilMisc.toMap("message","This is a test.");
try {
    long startTime = (new Date()).getTime();
    dispatcher.schedule("testScv", context, startTime);
} catch (GenericServiceException e) {     e.printStackTrace();


// This example will schedule a service to run now and repeat once every 5 seconds a total of 10 times.
Map context = UtilMisc.toMap("message","This is a test.");
try {
    long startTime = (new Date()).getTime();
    int frequency = RecurrenceRule.SECONDLY;
    int interval = 5;
    int count = 10;
    dispatcher.schedule("testScv", context, startTime, frequency, interval, count);
} catch (GenericServiceException e) {
    e.printStackTrace();
}

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The interface service engine has been implemented to help with defining services which share a number of the same parameters. An interface service cannot be invoked, but rather is a defined service which other services inherit from. Each interface service will be defined using the interface engine, for example:

<service name="testInterface" engine="interface" location="" invoke="">
    <description>A test interface service</description>
    <attribute name="partyId" type="String" mode="IN"/>
    <attribute name="partyTypeId" type="String" mode="IN"/>
    <attribute name="userLoginId" type="org.ofbiz.entity.GenericValue" mode="OUT" optional="true"/>
</service>

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Now that we have an interface we need to define a service which implements this interface

<service name="testExample1" engine="simple" location="org/ofbiz/commonapp/common/SomeTestFile.xml" invoke="testExample1">
    <description>A test service which implements testInterface</description>
    <implements service="testInterface"/>
</service>

The testExample1 service will have the exact same required and optional attributes as thetestInterface the testInterface service. Any service which implements testInterfacewill testInterface will also inherit the parameters/attributes. If needed, additional attributes can be added to a specific service by including the attribute tag along with the implementstag. You may also override an attribute by re-defining it after the implements tag.

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ECA (Event Condition Action) is much like a trigger. When a service is called, a lookup is performed to see if any ECAs are defined for this event. Events include before authentication, before IN parameter validation, before actual service invocation, before OUT parameter validation, before transaction commit, or before the service returns. Next each conditionin condition in the ECA definition is evaluated and if all come back as true, each actionis action is performed. An action is just a service which must be defined to work with the parameters already in the service's context. There are no limit to the number of conditions or actions each ECA may define.

<service-eca>
    <eca service="testScv" event="commit">
        <condition field-name="message" operator="equals" value="12345"/>
        <action service="testBsh" mode="sync"/>
    </eca>
</service-eca>

A tip from Parimal Gain Tip: Note that you may use the set operation to rename a parameter for the triggered service or insert values for instance...

    <eca service="setCustRequestStatus" event="commit">
        <condition field-name="oldStatusId" operator="not-equals" value="CRQ_ACCEPTED"/>
        <condition field-name="statusId" operator="equals" value="CRQ_ACCEPTED"/>
        <set field-name="bodyParameters.custRequestId" env-name="custRequestId"/>
        <set field-name="bodyParameters.custRequestName" env-name="custRequestName"/>
        <set field-name="partyIdTo" env-name="fromPartyId"/>
        <set field-name="emailTemplateSettingId" value="CUST_REQ_ACCEPTED"/>
        <action service="sendMailFromTemplateSetting" mode="sync" />
    </eca>

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The eca element should also have 0 or more condition or condition-fieldelements field elements and 1 or more action elements.

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The group definition is very simple, it contains a group elements along with 1 or more service elements. The group element contains a name attribute and a modeattribute mode attribute used to define how the group will function. The service element is much like the actionelement action element in an ECA, the difference being the default value for result-to-context.

<service-group>
    <group name="testGroup" send-mode="all">
        <invoke name="testScv" mode="sync"/>
        <invoke name="testBsh" mode="sync"/>
    </group>
</service-group>

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JMS services are much like HTTP services, except the service request is sent to a JMS topic/queue. The engineshould engine should be set to jms, the location should be the name of the jms-service defined in the serviceengine.xml file (see Service Config document), and the invoke should be the name of the service on the remote system you are requesting to run. JMS services by nature are asynchronous.

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