# Pojo Serializer and Deserializer

Use [PojoSerializer](https://github.com/ic4j/ic4j-candid/blob/master/src/main/java/org/ic4j/candid/pojo/PojoSerializer.java) and [PojoDeserializer](https://github.com/ic4j/ic4j-candid/blob/master/src/main/java/org/ic4j/candid/pojo/PojoDeserializer.java) to serialize and deserialize the annotated POJO (Plain Old Java Object) to and from Candid payload of type RECORD. 

Serializer and Deserializer will use Candid Java annotations to get the Candid Name and Type. 

A fully functional example using [PojoSerializer](https://github.com/ic4j/ic4j-candid/blob/master/src/main/java/org/ic4j/candid/pojo/PojoSerializer.java) and [PojoDeserializer](https://github.com/ic4j/ic4j-candid/blob/master/src/main/java/org/ic4j/candid/pojo/PojoDeserializer.java) can be found [here](https://github.com/ic4j/samples/tree/master/IC4JPojoSample).

This example calls a canister using Motoko [main.mo](https://github.com/ic4j/samples/blob/master/IC4JPojoSample/src/main.mo). 

The canister uses 2 complex types, **LoanApplication** and **LoanOffer.**

```javascript
 // Loan Application
public type LoanApplication = {
    id: Nat;
    firstname: Text;
    lastname: Text;
    zipcode: Text;
    ssn: Text;
    amount: Float;
    term: Nat16;
    created: Int;
 };

// Loan Offer
public type LoanOffer = {
    providerid: Principal;
    providername: Text;
    applicationid: Nat;
    apr: Float;
    created: Int;
};
```

The canister has 2 methods **apply** and **getOffers.**

```javascript
 public shared (msg) func apply(input : LoanApplication) : async LoanOffer { 
       counter += 1;
        Debug.print("Loan Application for user " #Principal.toText(msg.caller));
        
        let offer  : LoanOffer = {
            providerid = Principal.fromActor(this);
            providername = "Loan Provider";
            applicationid = counter;
            apr = 3.14;
            created = Time.now();
        };

        var userOffers :  ?Offers<LoanOffer> = offers.get(msg.caller);

        switch userOffers {
            case (null) { var userOffer : Offers<LoanOffer> = Buffer.Buffer(0); userOffer.add(offer);  offers.put(msg.caller, userOffer)};
            case (?userOffer) { userOffer.add(offer); };
        };
        return offer;
};

public query (msg) func getOffers() : async [LoanOffer] {
        var userOffers :  ?Offers<LoanOffer> = offers.get(msg.caller);

        switch userOffers {
            case (null) { return [] };
            case (?userOffer) { return userOffer.toArray() };
        };
};
```

To call this canister the annotated proxy Java interface [LoanProxy.java](https://github.com/ic4j/samples/blob/master/IC4JPojoSample/src/main/java/org/ic4j/samples/pojo/LoanProxy.java) and [ProxyBuilder](/reference/api-reference/proxybuilder.md) will be used.&#x20;

{% code title="LoanProxy.java" %}

```java
public interface LoanProxy {
	@UPDATE
	@Name("apply")
	@Waiter(timeout = 30)
	@ResponseClass(LoanOffer.class)
	public CompletableFuture<LoanOffer> apply(@Argument(Type.RECORD) LoanApplication loanApplication);
	
	@QUERY
	@Name("getOffers")
	public LoanOffer[] getOffers();
}
```

{% endcode %}

LoanApplication and LoanOffer Java classes with the Candid annotation are defined in [LoanApplication.java](https://github.com/ic4j/samples/blob/master/IC4JPojoSample/src/main/java/org/ic4j/samples/pojo/LoanApplication.java) and [LoanOffer.java](https://github.com/ic4j/samples/blob/master/IC4JPojoSample/src/main/java/org/ic4j/samples/pojo/LoanOffer.java).

{% code title="LoanApplication.java" %}

```java
public class LoanApplication{
    @Field(Type.NAT)
    public BigInteger id;
    public Double amount;
    @Field(Type.NAT16)    
    public Short term;
    @Name("firstname")
    public String firstName;
    @Name("lastname")
    public String lastName;
    public String ssn;
    public String zipcode;
    public BigInteger created;
}
```

{% endcode %}

{% code title="LoanOffer.java" %}

```java
public class LoanOffer{
    @Field(Type.PRINCIPAL)
    @Name("providerid")
    public String providerId;	
    @Name("providername")
    public String providerName;    
    @Field(Type.PRINCIPAL)
    @Name("userid")
    public Principal userId;
    @Field(Type.NAT)
    @Name("applicationid")
    public Integer applicationId;
    public Double apr;
    @Field(Type.INT)
    public Long created;
}
```

{% endcode %}

By default, **PojoSerializer** and **PojoDeserializer** will use [Java to Candid type mapping](/reference/api-reference/supported-types.md) and use the Java member variable name as the name of the Candid RECORD field.&#x20;

Use Candid annotations [@Field](https://github.com/ic4j/ic4j-candid/blob/master/src/main/java/org/ic4j/candid/annotations/Field.java) to override the default type and [@Name](https://github.com/ic4j/ic4j-candid/blob/master/src/main/java/org/ic4j/candid/annotations/Name.java) to override the default name.

To skip serialization and deserialization of certain member variables, use the [@Ignore](https://github.com/ic4j/ic4j-candid/blob/master/src/main/java/org/ic4j/candid/annotations/Ignore.java) annotation.

[ProxyBuilder](/reference/api-reference/proxybuilder.md) will implicitly use PojoSerializer and PojoDeserializer to convert Candid RECORD to a Java object.

{% code title="Main.java" %}

```java
LoanApplication loanApplication = new LoanApplication();
loanApplication.firstName = "John";
loanApplication.lastName = "Doe";
loanApplication.ssn = "111-11-1111";
loanApplication.term = 48;
loanApplication.zipcode = "95134";		
loanApplication.amount = (double) 20000.00;
loanApplication.id = new BigInteger("11");
loanApplication.created = new BigInteger("0");
		
LoanProxy loanProxy = ProxyBuilder
		.create(agent, Principal.fromString(icCanister))
		.getProxy(LoanProxy.class);
		
CompletableFuture<LoanOffer> response = loanProxy.apply(loanApplication);		
LoanOffer loanOffer = response.get();				
LOG.info("Loan Offer APR is " + loanOffer.apr);		
```

{% endcode %}

To use [Raw methods](/reference/api-reference/using-raw-agent-methods.md) or [QueryBuilder](/reference/api-reference/querybuilder-and-updatebuilder.md#querybuilder) and [UpdateBuilder](/reference/api-reference/querybuilder-and-updatebuilder.md#updatebuilder) use PojoSerializer and PojoDeserializer directly in the Java code.

{% code title="Main.java" %}

```java
IDLValue idlValue = IDLValue.create(loanApplication, new PojoSerializer());
List<IDLValue> args = new ArrayList<IDLValue>();
args.add(idlValue);
IDLArgs idlArgs = IDLArgs.create(args);

byte[] payload = idlArgs.toBytes();

CompletableFuture<byte[]> response = UpdateBuilder
	.create(agent, Principal.fromString(canisterid), "apply")
	.expireAfter(Duration.ofMinutes(3))
	.arg(payload)
	.callAndWait(Waiter.create(60, 5));
	
byte[] output = queryResponse.get();

LoanOffer loanOffer = IDLArgs.fromBytes(output).getArgs().get(0).getValue(new PojoDeserializer(), LoanOffer.class);	
```

{% endcode %}


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://docs.ic4j.com/reference/api-reference/object-serializers-and-deserializers/pojo-serializer-and-deserializer.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.