Developing with Java and Spring Boot using Amazon CodeWhisperer

Developers often have to work with multiple programming languages depending on the task at hand.  Sometimes, this is a result of choosing the right tool for a specific problem, or it is mandated by adhering to a specific technology adopted by a team.  Within a specific programming language, developers may have to work with frameworks, software libraries, and popular cloud services from providers such as Amazon Web Services (AWS). This must be done while adhering to secure and best programming practices.  Despite these challenges, developers must continue to release code at a sufficiently high velocity.    

 Amazon CodeWhisperer is a real-time, AI coding companion that provides code suggestions in your IDE code editor. Developers can simply write a comment that outlines a specific task in plain English, such as “method to upload a file to S3.” Based on this, CodeWhisperer automatically determines which cloud services and public libraries are best suited to accomplish the  task and recommends multiple code snippets directly in the IDE. The code is generated based on the context of your file, such as comments as well as surrounding source code and import statements. CodeWhisperer is available as part of the AWS Toolkit for Visual Studio Code and JetBrain family of IDEs.  CodeWhisperer is also available for AWS Cloud9, AWS Lambda console, JupyterLab, Amazon SageMaker Studio and AWS Glue Studio. CodeWhisperer supports popular programming languages like Java, Python, C#, TypeScript, GO, JavaScript, Rust, PHP, Kotlin, C, C++, Shell scripting, SQL, and Scala. 

 In this post, we will explore how to leverage CodeWhisperer in Java applications specifically using the Spring Boot framework. Spring Boot is an extension of the Spring framework that makes it easier to develop Java applications and microservices. Using CodeWhisperer, you will be spending less time creating boilerplate and repetitive code and more time focusing on business logic. You can generate entire Java Spring Boot functions and logical code blocks without having to search for code snippets from the web and customize them according to your requirements.  CodeWhisperer will enable you to responsibly use AI to create syntactically correct and secure Java Spring Boot applications. To enable CodeWhisperer in your IDE, please see Setting up CodeWhisperer for VS Code or Setting up Amazon CodeWhisperer for JetBrains depending on which IDE you are using.

 Note: Please note that CodeWhisperer uses artificial intelligence to provide code recommendations and this is non-deterministic. This code might differ from what you get from Amazon CodeWhisperer in your case.

Creating Data Transfer Objects (DTO)

Amazon CodeWhisperer makes it easier to develop the classes as you include import statements and provide brief comments on the purpose of the class.  Let’s start with the basics and develop a simple DTO or Plain Old Java Object (POJO).  This class will contain properties representing a product.  This DTO will be referenced later as part of a REST controller we generate to serialize the output to JSON.  CodeWhisperer will create a DTO class by using the class name and comments provided in plain language. Detailed and contextual comments will enable CodeWhisperer to generate code suggestions ranging from snippets to full functions in real time. For this use case, you are going to create a product class with id, name, price, description and rating properties.

 Type the following or similar comment in the class :

package com.amazonws.demo.cart.dto; //create a Product class with id, name, price, description and rating properties. 

After entering the comment and pressing ENTER, CodeWhisperer will start providing code suggestions. You can use the Tab key to accept a suggestion based on the context or use the left/right arrow keys to see more suggestions.  As shown below, the product class is auto generated with five properties id, name, price, rating and description with default getter/setter methods and two constructors. If you need more properties, you can either update the comment to include the new columns or manually create the columns in the file:

package com.amazonws.demo.cart.dto; //create a Product class with id, name, price, description and rating properties. public class Product { private String id; private String name; private Double price; private String description; private Integer rating; public Product() { } public Product(String id, String name, Double price) { this.id = id; this.name = name; setPrice(this.price = price); } public String getId() { return id; } public void setId(String id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public Double getPrice() { return price; } public void setPrice(Double price) { this.price = price; } public String getDescription(){ return description; } public void setDescription(String description){ this.description = description; } public Integer getRating(){ return rating; } public void setRating(Integer rating){ this.rating = rating; }
}

Implementing Data Access Object  (DAO) pattern

Next, we implement the DAO pattern in this case for Amazon DynamoDB. The DAO pattern allows you to decouple the application/business layers from the persistence layer. It contains all the implementation logic for interacting with the persistence layer. We will create an entity class which represents the data to persist in DynamoDB along with the DAO class which contains the persistence logic.

 First, create a ProductDaoEntity class which maps to the Amazon DynamoDB table. Create a blank ProductDaoEntity class and import DynamoDB packages for annotations, attributes, and partition key, as shown below. Notice that the class has a comment about the class structure and use of the DynamoDB enhanced client, so that CodeWhisperer can provide meaningful suggestion. The enhanced client allows you to map client-side classes to DynamoDB tables.

package com.amazonws.demo.cart.dao.entity; import software.amazon.awssdk.enhanced.dynamodb.mapper.annotations.DynamoDbAttribute;
import software.amazon.awssdk.enhanced.dynamodb.mapper.annotations.DynamoDbBean;
import software.amazon.awssdk.enhanced.dynamodb.mapper.annotations.DynamoDbPartitionKey;
import software.amazon.awssdk.enhanced.dynamodb.mapper.annotations.DynamoDbSortKey; //create a dynamo db ProductDaoEntity class with partition Key as id, name, price, description, rating attributes using dynamo db enhanced mapper annotations

CodeWhisperer can now infer the comments, contexts, and import statements and start to generate the class implementation. You can accept or reject comments based on your requirements. Below, you can see the complete class generated by CodeWhisperer.

@DynamoDbBean
public class ProductDaoEntity { private String id; private String name; private double price; private String description; private int rating; public ProductDaoEntity() { } public ProductDaoEntity(String id, String name, double price, String description, int rating) { this.id = id; this.name = name; this.price = price; this.description = description; this.rating = rating; } @DynamoDbPartitionKey @DynamoDbAttribute("id") public String getId() { return id; } public void setId(String id) { this.id = id; } @DynamoDbSortKey @DynamoDbAttribute("name") public String getName() { return name; } public void setName(String name) { this.name = name; } @DynamoDbAttribute("price") public double getPrice() { return price; } public void setPrice(double price) { this.price = price; } @DynamoDbAttribute("description") public String getDescription() { return description; } public void setDescription(String description) { this.description = description; } @DynamoDbAttribute("rating") public int getRating() { return rating; } public void setRating(int rating) { this.rating = rating; } @Override public String toString() { return "ProductDaoEntity [id=" + id + ", name=" + name + ", price=" + price + ", description=" + description + ", rating=" + rating + "]"; } }

Notice how CodeWhisperer includes the appropriate DynamoDB related annotations such as @DynamoDbBean, @DynamoDbPartitionKey, @DynamoDbSortKey and @DynamoDbAttribute. This will be used to generate a TableSchema for mapping classes to tables.

 Now that you have the mapper methods completed, you can create the actual persistence logic that is specific to DynamoDB. Create a class named ProductDaoImpl. (Note: it’s a best practice for DAOImpl class to implement a DAO interface class.  We left that out for brevity.) Using the import statements and comments, CodeWhisperer can auto-generate most of the DynamoDB persistence logic for you. Create a ProductDaoImpl class which uses a DynamoDbEnhancedClient object as shown below.

package com.amazonws.demo.cart.dao; import javax.annotation.PostConstruct;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component; import com.amazonws.demo.cart.dao.Mapper.ProductMapper;
import com.amazonws.demo.cart.dao.entity.ProductDaoEntity;
import com.amazonws.demo.cart.dto.Product; import software.amazon.awssdk.core.internal.waiters.ResponseOrException;
import software.amazon.awssdk.enhanced.dynamodb.DynamoDbEnhancedClient;
import software.amazon.awssdk.enhanced.dynamodb.DynamoDbTable;
import software.amazon.awssdk.enhanced.dynamodb.Key;
import software.amazon.awssdk.enhanced.dynamodb.TableSchema; @Component
public class ProductDaoImpl{ private static final Logger logger = LoggerFactory.getLogger(ProductDaoImpl.class); private static final String PRODUCT_TABLE_NAME = "Products"; private final DynamoDbEnhancedClient enhancedClient; @Autowired public ProductDaoImpl(DynamoDbEnhancedClient enhancedClient){ this.enhancedClient = enhancedClient; }

Rather than providing comments that describe the functionality of the entire class, you can provide comments for each specific method here. You will use CodeWhisperer to generate the implementation details for interacting with DynamoDB.  If the Products table doesn’t already exist, you will need to create it. Based on the comment, CodeWhisperer will generate a method to create a a Products table if one does not exist.  As you can see, you don’t have to memorize or search through the DynamoDB API documentation to implement this logic. CodeWhisperer will save you time and effort by giving contextualized suggestions.

//Create the DynamoDB table through enhancedClient object from ProductDaoEntity. If the table already exists, log the error. @PostConstruct public void createTable() { try { DynamoDbTable<ProductDaoEntity> productTable = enhancedClient.table(PRODUCT_TABLE_NAME, TableSchema.fromBean(ProductDaoEntity.class)); productTable.createTable(); } catch (Exception e) { logger.error("Error creating table: ", e); } }

Now, you can create the CRUD operations for the Product object. You can start with the createProduct operation to insert a new product entity to the DynamoDB table. Provide a comment about the purpose of the method along with relevant implementation details.

 // Create the createProduct() method // Insert the ProductDaoEntity object into the DynamoDB table // Return the Product object

CodeWhisperer will start auto generating the Create operation as shown below. You can accept/reject the suggestions as needed. Or, you may select from alternate suggestion if available using the left/right arrow keys.

 // Create the createProduct() method // Insert the ProductDaoEntity object into the DynamoDB table // Return the Product object public ProductDaoEntity createProduct(ProductDaoEntity productDaoEntity) { DynamoDbTable<ProductDaoEntity> productTable = enhancedClient.table(PRODUCT_TABLE_NAME, TableSchema.fromBean(ProductDaoEntity.class)); productTable.putItem(productDaoEntity); return product; } 

Similarly, you can generate a method to return a specific product by id. Provide a contextual comment, as shown below.

// Get a particular ProductDaoEntity object from the DynamoDB table using the // product id and return the Product object

Below is the auto-generated code. CodeWhisperer has correctly analyzed the comments and generated the method to get a Product by its id.

 //Get a particular ProductDaoEntity object from the DynamoDB table using the // product id and return the Product object public ProductDaoEntity getProduct(String productId) { DynamoDbTable<ProductDaoEntity> productTable = enhancedClient.table(PRODUCT_TABLE_NAME, TableSchema.fromBean(ProductDaoEntity.class)); ProductDaoEntity productDaoEntity = productTable.getItem(Key.builder().partitionValue(productId).build()); return productDaoEntity; }

Similarly, you can implement the DAO layer to delete and update products using DynamoDB table.

Creating a Service Object

Next, you will generate the ProductService class which retrieves the Product using ProductDAO.  In Spring Boot, a class annotated with @Service allows it to be detected through classpath scanning.

Let’s provide a comment to generate the ProductService class:

package com.amazonws.demo.cart.service; import java.util.List; import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service; import com.amazonws.demo.cart.dto.Product;
import com.amazonws.demo.cart.dao.ProductDao; //Create a class called ProductService with methods: getProductById(string id),
//getAllProducts(), updateProduct(Product product), //deleteProduct(string id), createProduct(Product product)

CodeWhisperer will create the following class implementation.  Note, you may have to adjust return types or method parameter types as needed.  Notice the @Service annotation for this class along with the productDao property being @Autowired.

@Service
public class ProductService { @Autowired ProductDao productDao; public Product getProductById(String id) { return productDao.getProductById(id); } public List<Product> getProducts() { return productDao.getAllProducts(); } public void updateProduct(Product product) { productDao.updateProduct(product); } public void deleteProduct(String id) { productDao.deleteProduct(id); } public void createProduct(Product product) { productDao.createProduct(product); } }

Creating a REST Controller

The REST controller typically handles incoming client HTTP requests and responses and its output is typically serialized into JSON or XML formats.  Using annotations, Spring Boot maps the HTTPS methods such as GET, PUT, POST, and DELETE to appropriate methods within the controller.  It also binds the HTTP request data to parameters defined within the controller methods.

Provide a comment as shown below specifying that the class is a REST controller that should support CORS along with the required methods.

package com.amazonws.demo.product.controller; import java.util.List; import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.CrossOrigin;
import org.springframework.web.bind.annotation.DeleteMapping;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.PutMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController; import com.amazonws.demo.product.dto.Product;
import com.amazonws.demo.product.service.ProductService; //create a RestController called ProductController to get all
//products, get a product by id, create a product, update a product,
//and delete a product. support cross origin requests from all origins. 

Notice how the appropriate annotations are added to support CORS along with the mapping annotations that correspond with the GET, PUT, POST and DELETE HTTP methods. The @RestController annotation is used to specify that this controller returns an object serialized as XML or JSON rather than a view.

@RestController
@RequestMapping("/product")
@CrossOrigin(origins = "*")
public class ProductController { @Autowired private ProductService productService; @GetMapping("/getAllProducts") public List<Product> getAllProducts() { return productService.getAllProducts(); } @GetMapping("/getProductById/{id}") public Product getProductById(@PathVariable String id) { return productService.getProductById(id); } @PostMapping("/createProduct") public Product createProduct(@RequestBody Product product) { return productService.createProduct(product); } @PutMapping("/updateProduct") public Product updateProduct(@RequestBody Product product) { return productService.updateProduct(product); } @DeleteMapping("/deleteProduct/{id}") public void deleteProduct(@PathVariable String id) { productService.deleteProduct(id); } }

Conclusion

In this post, you have used CodeWhisperer to generate DTOs, controllers, service objects, and persistence classes. By inferring your natural language comments, CodeWhisperer will provide contextual code snippets to accelerate your development.  In addition, CodeWhisperer has additional features like reference tracker that detects whether a code suggestion might resemble open-source training data and can flag such suggestions with the open-source project’s repository URL, file reference, and license information for your review before deciding whether to incorporate the suggested code.

Try out Amazon CodeWhisperer today to get a head start on your coding projects.