@Payload annotation controls how the current message payload is passed into a method by performing automatic transformation of the message payload to match the annotated parameter type. A parameter injection annotation that can be used on component entry points.

The primary goal of this article is to retrieve the JSON payload in the Java component using the@Payload annotation.

I created a Book POJO class under src/main/java.

package com.ss.component;

public class Book {

 private String title;
 private String author;
 private double price;

 public String getTitle() {
  return title;
 }
 public void setTitle(String title) {
  this.title = title;
 }
 public String getAuthor() {
  return author;
 }
 public void setAuthor(String author) {
  this.author = author;
 }
 public double getPrice() {
  return price;
 }
 public void setPrice(double price) {
  this.price = price;
 }
 @Override
 public String toString() {
  return "Book [title=" + title + ", author=" + author + ", price=" + price + "]";
 }
}

...and a component class as:

package com.ss.component;

import org.mule.api.annotations.param.Payload;

public class MyComponent {
 public Object process(@Payload Book book) {
  System.out.println("Title:" + book.getTitle());
  System.out.println("Author:" + book.getAuthor());
  System.out.println("Price:" + book.getPrice());

  return book;
 }
}

Develop the flow as follows:

<?xml version="1.0" encoding="UTF-8"?>
<mule
	xmlns:json="http://www.mulesoft.org/schema/mule/json"
	xmlns:http="http://www.mulesoft.org/schema/mule/http"
	xmlns="http://www.mulesoft.org/schema/mule/core"
	xmlns:doc="http://www.mulesoft.org/schema/mule/documentation"
	xmlns:spring="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-current.xsd
http://www.mulesoft.org/schema/mule/core http://www.mulesoft.org/schema/mule/core/current/mule.xsd
http://www.mulesoft.org/schema/mule/http http://www.mulesoft.org/schema/mule/http/current/mule-http.xsd
http://www.mulesoft.org/schema/mule/json http://www.mulesoft.org/schema/mule/json/current/mule-json.xsd">
	<http:listener-config name="HTTP_Listener_Configuration" host="localhost" port="9001" doc:name="HTTP Listener Configuration"/>
	<flow name="component_annotationFlow">
		<http:listener config-ref="HTTP_Listener_Configuration" path="/" doc:name="HTTP" allowedMethods="POST"/>
		<json:json-to-object-transformer returnClass="com.ss.component.Book" doc:name="JSON to Object"/>
		<component doc:name="Java">
			<singleton-object class="com.ss.component.MyComponent"/>
		</component>
		<object-to-string-transformer doc:name="Object to String"/>
		<logger message="#[payload]" level="INFO" doc:name="Logger"/>
	</flow>
</mule>

And here's the flow diagram:

Run and deploy the flow to Anypoint runtime.

Test the flow with the POSTMAN plug-in:

Hit the HTTP URL with a POST request with a JSON body as:

      {
        "title": "programming in c",
        "author": "bala guru swamy",
        "price": "100"
      }

We can observe output in the console as:

• Title: programming in c. 

• Author: bala guru swamy. 

• Price: 100.

INFO 2017-03-24 16:30:11,640:

[[component_annotation].HTTP_Listener_Configuration.worker .01]
org.mule.api.processor.LoggerMessageProcessor: Book[title = programming in c, author = bala guru swamy, price = 100.0]

Now, we have accessed the JSON payload in a Java component.