---
title: 'Model'
weight: 20
---
## Model
Before we dive into the entire model, let's show an example and how it would
be modelled in Strolch and use in Strolch:
A possible model would look as follows:
```xml
```
Let's go through this model:
* In the above model we see that the id and name fields are always on the
element, and thus aren't added as parameters. Further most elements have a
parameters ParameterBag, with one or more parameters, modelling the fields.
* Note that in this example the Type of all the elements is Template. Strolch
has API support to create a clone of these elements, so that they have a
unique ID, and the proper type for persistence.
* The Product element has three parameters: description, color and form. In
this case they are all of type String. Further the relations ParameterBag
defines the relationships, i.e. the product knows its articles. Note how
the relation is first defined in a relations ParameterBag and that the
Parameter has Interpretation="Resource-Ref" Uom="Product" attributes.
Strolch has API support for this, making it trivial to retrieve a dependency.
* The Article element has two parameters description and barcode. Further it
has a reference to its Product.
* The Order element doesn't model the date and state fields as parameters, as
these are inherently part of an Order element. The Order does define two
references to customer and articles. A special case is the quantities
ParameterBag. This bag of parameters is used to store the per article
quantity for this order. With ParameterBags, you can eliminate the use of
simple aggregate classes, as is commonly used in object-oriented programming.
* The Customer element models a address ParameterBag to store the address of
a customer. Using a separate bag allows for further more direct fields to
stored on the default parameters bag.
Now that we have a basic understanding of te model, it is of far more interest
in how to create and interact with these elements at runtime. The following
listing will perform simple operations:
```java
try (StrolchTransaction tx = runtimeMock.openUserTx(certificate, false)) {
/*
* create a new product
*/
Resource dafalgan = tx.getResourceTemplate("Product", true);
dafalgan.setName("Dafalgan 100mg");
dafalgan.getParameter("description", true).setValue("Dafalgan is for pain.");
dafalgan.getParameter("color", true).setValue("Yellow");
dafalgan.getParameter("form", true).setValue("flat");
StringListParameter articlesP = dafalgan.getRelationsParam("articles", true);
/*
* create articles
*/
Resource dafalgan1 = tx.getResourceTemplate("Article", true);
dafalgan1.setName("Dafalgan 100mg 10 pce");
dafalgan1.getParameter("description", true).setValue("This is pack with 10 pieces.");
dafalgan1.getParameter("barcode", true).setValue("654654");
Resource dafalgan2 = tx.getResourceTemplate("Article", true);
dafalgan2.setName("Dafalgan 100mg 20 pce");
dafalgan2.getParameter("description", true).setValue("This is pack with 20 pieces.");
dafalgan2.getParameter("barcode", true).setValue("654655");
/*
* add reference to product
*/
dafalgan1.getRelationParam("product").setValue(dafalgan.getId());
articlesP.addValue(dafalgan1.getId());
dafalgan2.getRelationParam("product").setValue(dafalgan.getId());
articlesP.addValue(dafalgan2.getId());
/*
* create a new customer
*/
Resource customer1 = tx.getResourceTemplate("Customer", true);
customer1.setName("John Doe");
// set address
ParameterBag addressBag = customer1.getParameterBag("address", true);
addressBag.getParameter("street", true).setValue("Main Str. 1");
addressBag.getParameter("zip", true).setValue("1234");
addressBag.getParameter("city", true).setValue("Hometown");
addressBag.getParameter("country", true).setValue("Switzerland");
/*
* create a new order
*/
Order order = tx.getOrderTemplate("Order", true);
order.setName("Order for " + customer1.getName());
order.setDate(LocalDate.of(2021, 2, 1));
order.setState(State.PLANNED);
// store reference to customer
order.getRelationParam("customer", true).setValue(customer1.getId());
StringListParameter orderArticlesP = order.getRelationsParam("articles", true);
ParameterBag quantitiesBag = order.getParameterBag("quantities", true);
FloatParameter quantityT = quantitiesBag.removeParameter("quantity");
// order quantity of 20 for Dafalgan 1
FloatParameter q1P = quantityT.getClone();
q1P.setId(dafalgan1.getId());
q1P.setValue(20);
quantitiesBag.addParameter(q1P);
orderArticlesP.addValue(dafalgan1.getId());
// set order quantity of 10 for Dafalgan 2
FloatParameter q2P = quantityT.getClone();
orderArticlesP.addValue(dafalgan2.getId());
q2P.setId(dafalgan2.getId());
q2P.setValue(20);
quantitiesBag.addParameter(q2P);
// keep IDs for later use
dafalganId = dafalgan.getId();
dafalgan1Id = dafalgan1.getId();
dafalgan2Id = dafalgan2.getId();
customerId = customer1.getId();
orderId = order.getId();
/*
* persist
*/
tx.add(dafalgan);
tx.add(dafalgan1);
tx.add(dafalgan2);
tx.add(customer1);
tx.add(order);
// commit
tx.commitOnClose();
}
```
```java
try (StrolchTransaction tx = runtimeMock.openUserTx(certificate, true)) {
// get order
Order order = tx.getOrderBy("Order", orderId, true);
assertNotNull(orderId);
assertEquals("Order for John Doe", order.getName());
// get customer
Resource customer = tx.getResourceByRelation(order, "customer", true);
assertNotNull(customer);
assertEquals("John Doe", customer.getName());
// get articles
List articles = tx.getResourcesByRelation(order, "articles", true);
assertEquals(2, articles.size());
// get products
List products = articles.stream().map(a -> tx.getResourceByRelation(a, "product", true))
.distinct().collect(Collectors.toList());
assertEquals(1, products.size());
// search for all orders in state PLANNED and with customer
List orders = new OrderSearch().types("Order").stateIsIn(State.PLANNED)
.where(ExpressionsSupport.relationParam("customer").isEqualTo(customerId)).search(tx).toList();
assertEquals(1, orders.size());
}
```
{{% notice tip %}}
Note: Checkout [example-model.xml](https://github.com/4treesCH/strolch/blob/develop/li.strolch.service/src/test/resources/transienttest/data/example-model.xml "{target='_blank'}") and [SimpleModelTest.java](https://github.com/4treesCH/strolch/blob/develop/li.strolch.service/src/test/java/li/strolch/service/SimpleModelTest.java "{target='_blank'}") for these examples.
{{% /notice %}}
{{% notice tip %}}
There is an XML Schema which defines the model in XML: [StrolchModel-1.6.xsd](/assets/xsd/StrolchModel-1.6.xsd "{target='_blank'}")
{{% /notice %}}
Here is an example of all the possible elements in Strolch:
```xml
```