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# Parsers and Serializers

HAPI FHIR has built-in support for the FHIR [JSON](http://hl7.org/fhir/json.html) and [XML](http://hl7.org/fhir/json.html) encoding formats.

A built in parser can be used to convert HAPI FHIR Java objects into a serialized form, and to parse serialized data into Java objects. Note that unlike some other frameworks, HAPI FHIR does not have separate parsers and serializers. Both of these functions are handled by a single object called the **Parser**.

# Parsing (aka Deserializing)

As with many parts of the HAPI FHIR API, parsing begins with a [FhirContext](/apidocs/hapi-fhir-base/ca/uhn/fhir/context/FhirContext.html) object. The FhirContext can be used to request an [IParser](/apidocs/hapi-fhir-base/ca/uhn/fhir/parser/IParser.html) for your chosen encoding style that is then used to parse.

```java
{{snippet:classpath:/ca/uhn/hapi/fhir/docs/Parser.java|parsing}}
``` 
   
# Encoding (aka Serializing)

As with many parts of the HAPI FHIR API, parsing begins with a [FhirContext](/apidocs/hapi-fhir-base/ca/uhn/fhir/context/FhirContext.html) object. The FhirContext can be used to request an [IParser](/apidocs/hapi-fhir-base/ca/uhn/fhir/parser/IParser.html) for your chosen encoding style that is then used to serialize.   

The following example shows a JSON Parser being used to serialize a FHIR resource. 

```java
{{snippet:classpath:/ca/uhn/hapi/fhir/docs/Parser.java|encoding}}
``` 
   
## Pretty Printing

By default, the parser will output in condensed form, with no newlines or indenting. This is good for machine-to-machine communication since it reduces the amount of data to be transferred but it is harder to read. To enable pretty printed output:

When using the [HAPI FHIR Server](../server_plain/), pretty printing can be requested by adding the parameter _pretty=true to the request.

```java
{{snippet:classpath:/ca/uhn/hapi/fhir/docs/Parser.java|encodingPretty}}
``` 

## Encoding Configuration

There are plenty of other options too, that can be used to control the output by the parser. A few examples are shown below. See the [IParser](/apidocs/hapi-fhir-base/ca/uhn/fhir/parser/IParser.html) JavaDoc for more information.

```java
{{snippet:classpath:/ca/uhn/hapi/fhir/docs/Parser.java|encodingConfig}}
``` 

## Summary Mode

For each resource type, the FHIR specification defines a collection of elements which are considered "summary elements". These are marked on the individual resource views using a Sigma (Σ) symbol next to the element names. See the [Patient Resource Definition](https://hl7.org/fhir/patient.html) for an example, looking for
this symbol on the page.

If the parser is configured as shown below, only the summary mode elements will be included in the encoded resource. 

When using the [HAPI FHIR Server](../server_plain/), summary mode can be requested by adding the parameter _summary=true to the request.

```java
{{snippet:classpath:/ca/uhn/hapi/fhir/docs/Parser.java|encodingSummary}}
``` 



# Global Parser Configuration

It is possible to configure a number of parser settings globally for a given FhirContext, meaning that they will apply to all parsers that are created by that context. This is especially useful for [HAPI FHIR Clients](../client/) and [HAPI FHIR Servers](../server_plain/), where parsers are created by the client/server internally using the given FhirContext.  

```java
{{snippet:classpath:/ca/uhn/hapi/fhir/docs/Parser.java|globalParserConfig}}
```