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# Narrative Generation

HAPI provides several ways to add [Narrative Text](http://hl7.org/fhir/narrative.html) to your encoded messages.

The simplest way is to place the narrative text directly in the resource via the `setDivAsString()` method.

```java
{{snippet:classpath:/ca/uhn/hapi/fhir/docs/Narrative.java|simple}}
```

# Automatic Narrative Generation

HAPI FHIR also comes with a built-in mechanism for automatically generating narratives based on your resources.

**Warning:** This built-in capability is a work in progress, and does not cover every type of resource or even every attribute in any resource. You should test it and configure it for your particular use cases.

HAPI's built-in narrative generation uses the [Thymeleaf](http://www.thymeleaf.org/) library for templating narrative texts. Thymeleaf provides a simple XHTML-based syntax which is easy to use and meshes well with the HAPI-FHIR model objects.

## A Simple Example

Activating HAPI's built-in narrative generator is as simple as calling [setNarrativeGenerator](/hapi-fhir/apidocs/hapi-fhir-base/ca/uhn/fhir/context/FhirContext.html#setNarrativeGenerator(ca.uhn.fhir.narrative.INarrativeGenerator)).

```java
{{snippet:classpath:/ca/uhn/hapi/fhir/docs/Narrative.java|example1}}
```

...which produces the following output:

```xml

    
        
        
             John Edward SMITH 
            
                
                    Identifier 7000135
                    Address 742 Evergreen Terrace
Springfield ZZ
                
            
        
    
    

```

# Built-in Narrative Templates

HAPI currently only comes with built-in support for a few resource types. Our intention is that people enhance these templates and create new ones, and share these back with us so that we can continue to build out the library. To see the current template library, see the source repository [here](https://github.com/hapifhir/hapi-fhir/tree/master/hapi-fhir-base/src/main/resources/ca/uhn/fhir/narrative).

Note that these templates expect a few specific CSS definitions to be present in your site's CSS file. See the [narrative CSS](https://github.com/hapifhir/hapi-fhir/blob/master/hapi-fhir-base/src/main/resources/ca/uhn/fhir/narrative/hapi-narrative.css) to see these.

# Creating your own Templates

To use your own templates for narrative generation, simply create one or more templates, using the Thymeleaf HTML based syntax.

```html
{{snippet:classpath:/ca/uhn/hapi/fhir/docs/snippet/OperationOutcome.html}}
```

Then create a properties file which describes your templates. In this properties file, each resource to be defined has a pair or properties.

The first (name.class) defines the class name of the resource to define a template for. The second (name.narrative) defines the path/classpath to the template file. The format of this path is `file:/path/foo.html` or  `classpath:/com/classpath/foo.html`.

```properties
# Two property lines in the file per template. There are several forms you
# can use. This first form assigns a template type to a resource by 
# resource name
practitioner.resourceType=Practitioner
practitioner.narrative=classpath:com/example/narrative/Practitioner.html

# This second form assigns a template by class name. This can be used for
# HAPI FHIR built-in structures, or for custom structures as well.
observation.class=org.hl7.fhir.r4.model.Observation
observation.narrative=classpath:com/example/narrative/Observation.html

# You can also assign a template based on profile ID (Resource.meta.profile)
vitalsigns.profile=http://hl7.org/fhir/StructureDefinition/vitalsigns
vitalsigns.narrative=classpath:com/example/narrative/Observation_Vitals.html
```

You may also override/define behaviour for datatypes and other structures. These datatype narrative definitions will be used as content within th:narrative blocks in resource templates. See the [example above](#creating-your-own-templates).

```properties
# You can create a template based on a type name
quantity.dataType=Quantity
quantity.narrative=classpath:com/example/narrative/Quantity.html

string.dataType=String
string.narrative=classpath:com/example/narrative/String.html

# Or by class name, which can be useful for custom datatypes and structures
custom_extension.class=com.example.model.MyCustomExtension
custom_extension.narrative=classpath:com/example/narrative/CustomExtension.html
```

Finally, use the [CustomThymeleafNarrativeGenerator](/hapi-fhir/apidocs/hapi-fhir-base/ca/uhn/fhir/narrative/CustomThymeleafNarrativeGenerator.html) and provide it to the FhirContext.

```java
{{snippet:classpath:/ca/uhn/hapi/fhir/docs/NarrativeGenerator.java|gen}}
```

# Fragments Expressions in Thymeleaf Templates

Thymeleaf has a concept called Fragments, which allow reusable template portions that can be imported anywhere you need them. It can be helpful to put these fragment definitions in their own file. For example, the following property file declares a template and a fragment:

```properties
{{snippet:classpath:ca/uhn/fhir/narrative/narrative-with-fragment.properties}}
```

The following template declares `Fragment1` and `Fragment2` as part of file `narrative-with-fragment-child.html`: 

```html
{{snippet:classpath:ca/uhn/fhir/narrative/narrative-with-fragment-child.html}}
```

And the following parent template (`narrative-with-fragment-parent.html`) imports `Fragment1` with parameter 'blah':

```html
{{snippet:classpath:ca/uhn/fhir/narrative/narrative-with-fragment-parent.html}}
```


# FHIRPath Expressions in Thymeleaf Templates

Thymeleaf templates can incorporate FHIRPath expressions using the `#fhirpath` expression object.

This object has the following methods:

* evaluateFirst(input, pathExpression) – This method returns the first element matched on `input` by the path expression, or _null_ if nothing matches. 
* evaluate(input, pathExpression) – This method returns a Java List of elements matched on `input` by the path expression, or an empty list if nothing matches. 

For example:

```html
{{snippet:classpath:ca/uhn/fhir/narrative/narratives-with-fhirpath-evaluate-single-primitive.html}}
```
Identifier	7000135
Address	742 Evergreen Terrace Springfield ZZ