[HW] <Vaibhav E>

[vaibhav231093]

Name: Vaibhav E Email: e.vaibhav93@gmail.com Linkedin Profile: https://www.linkedin.com/in/vaibhav231093

Step 1 : Set up the server

Step 1a : unzip demo.zip and open DemoApplication.java

Step 1b : Run the project in the terminal with the following command.

cd /root/demo 
mvn spring-boot:run 

Step 1c : Run the below command in the second terminal curl 127.0.0.1:8080/ | jq

Expected Output :

Step 2 : Add a simple response

Step 2a : Modify DemoApplication.java by adding request mapping method, changing class annotations and fix up the imports like below. Open demo/src/main/java/com/example/demo/DemoApplication.java

`package com.example.demo; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.; import org.springframework.web.bind.annotation.;

@RestController @EnableAutoConfiguration public class DemoApplication {

public static void main(String[] args) { SpringApplication.run(DemoApplication.class, args); }

@RequestMapping("/") String home() { return "Home\n"; }

// TODO: add Hello handler here }`

Step 2b : Run the below command in the terminal 1 # Sending a Ctrl-C to stop the server

Step 2c : Run the below command to start the server mvn spring-boot:run

Step 2d : Run the below command to see the expected output (i.e, Home) curl 127.0.0.1:8080/

Expected Output :

Step 3 : Create a parameterized response

Step 3a : Modify DemoApplication.java to add a response for the /hello endpoint

Open demo/src/main/java/com/example/demo/DemoApplication.java

@RequestMapping("/hello") String hello() { return "Hello World\n"; }

Step 3 b : Run the below command to restart the terminal 1

# Sending a Ctrl-C and restarting the server
mvn spring-boot:run

Step 3c : Run the below command to see the hello endpoint output curl 127.0.0.1:8080/hello

Expected Output :

Step 3d : We can customize the end point by adding a parameter. We'll pass the parameter into our handler method using the @RequestParam annotation, which also allows us to set a default value.

`package com.example.demo; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.; import org.springframework.web.bind.annotation.;

@RestController @EnableAutoConfiguration public class DemoApplication {

public static void main(String[] args) { SpringApplication.run(DemoApplication.class, args); }

@RequestMapping("/hello") String hello(@RequestParam(value = "name", defaultValue = "World") String name) { return String.format("Hello %s!\n", name); }

@RequestMapping("/") String home() { return "Home\n"; } } `

Step 3e : Back in terminal 1, restart the server. # Sending a Ctrl-C and restarting the server mvn spring-boot:run

Step 3f : In terminal 2, first try the endpoint with no parameter to see the default behavior (Hello World!). Run the below command curl 127.0.0.1:8080/hello

Expected Output:

Step 3g: Now, try it with a parameter to see a greeting for Alex (Hello Alex!). curl 127.0.0.1:8080/hello?name=Alex

Expected Output:

Step 4 : Access Cassandra from Java

Step 4a : To put things in context, let's see how we can access a Cassandra cluster using the Java driver.

Let's start by creating a user_credentials table. We've already installed and started Cassandra for you, so just execute the following to create the keyspace and table.

export PATH="/root/apache-cassandra-4.0-beta2/bin:$PATH" cqlsh -e " CREATE KEYSPACE user_management WITH REPLICATION = { 'class' : 'SimpleStrategy', 'replication_factor' : 1 }; CREATE TABLE user_management.user_credentials( username text, password text, PRIMARY KEY(username));"

Step 4b : We can add a handful of records to the table.

cqlsh -e " INSERT INTO user_management.user_credentials (username, password) VALUES ('User1', 'YouWontGuessThis'); INSERT INTO user_management.user_credentials (username, password) VALUES ('User2', 'SuperSecret'); INSERT INTO user_management.user_credentials (username, password) VALUES ('User3', 'UncrackablePassword');"

Step 4c : Next, let's create a Java program to access the table. We'll start by setting up a Maven project mvn archetype:generate -DgroupId=com.datastax -DartifactId=driver-example -Dversion=1.0-SNAPSHOT -DinteractiveMode=false

Step 4d : Open App.java Open driver-example/src/main/java/com/datastax/App.java

Step 4e : Maven projects use a pom.xml file to keep track of dependencies, etc. Inspect the pom.xml for this project

Open driver-example/pom.xml

`

1.8 1.8 `  **Step 4f : We need to modify pom.xml to include the Java driver.** `Open driver-example/pom.xml` ` com.datastax.oss java-driver-core 4.8.0 org.slf4j slf4j-api 1.7.5 org.slf4j slf4j-simple 1.6.4 `  **Step 4g : Let's run the program just to make sure everything is set up correctly.** `cd /root/driver-example mvn compile exec:java -Dexec.mainClass=com.datastax.App 2> /dev/null`  **Step 4h : Let's go back to the Java program. We'll modify the Java program to query the cluster. Here's the code.** `Open driver-example/src/main/java/com/datastax/App.java` `package com.datastax; import com.datastax.oss.driver.api.core.CqlSession; import com.datastax.oss.driver.api.core.cql.*; /** * Hello world! * */ public class App { public static void main( String[] args ) { System.out.println( "Starting a query!" ); try (CqlSession session = CqlSession.builder().build()) { ResultSet rs = session.execute("select * from user_management.user_credentials"); for (Row row: rs) { System.out.println("username = "+row.getString("username") + ", password = " + row.getString("password")); } } } }`  We see that this query code sets up a CqlSession, and then uses the session to execute a CQL query to retrieve all users. **Step 4i : Run this query program in the terminal** `mvn compile exec:java -Dexec.mainClass=com.datastax.App 2> /dev/null cd /root` **Expected Output :**  ### Step 5 : Create a simple REST service **Step 5a : Open DemoApplication.java . We'll create a /users endpoint and query our Cassandra table for the response. Then, we'll convert the response to JSON and return it to create a simple REST service.** `package com.example.demo; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.*; import org.springframework.web.bind.annotation.*; import com.datastax.oss.driver.api.core.CqlSession; import com.datastax.oss.driver.api.core.cql.*; import com.google.gson.Gson; import java.util.*; @RestController @EnableAutoConfiguration public class DemoApplication { @RequestMapping("/hello") String hello(@RequestParam(value = "name", defaultValue = "World") String name) { return String.format("Hello %s!\n", name); } @RequestMapping("/users") String users() { ArrayList> results = new ArrayList>(); String result = ""; try (CqlSession session = CqlSession.builder().build()) { ResultSet rs = session.execute("select * from user_management.user_credentials"); result = "["; for (Row row: rs) { HashMap record = new HashMap(); record.put("username", row.getString("username")); record.put("password", row.getString("password")); results.add(record); } } Gson g = new Gson(); return g.toJson(results); } @RequestMapping("/") String home() { return "Home\n"; } public static void main(String[] args) { SpringApplication.run(DemoApplication.class, args); } }` **Step 5b : We need to add some dependencies to pom.xml for the Cassandra Java driver and for Gson (Gson is a utility that converts Java objects to JSON).** `Open demo/pom.xml` The dependencies include the Cassandra driver, some logging utilities and Gson. ` com.datastax.oss java-driver-core org.slf4j slf4j-api 1.7.5 org.slf4j slf4j-simple 1.6.4 com.google.code.gson gson `  **Step 5c : Restart the server and wait for it to initialize.** `# Sending a Ctrl-C and restarting the server mvn spring-boot:run` **Step 5d : Finally, let's test the simple REST endpoint that retrieves all users. Run the below command in the terminal** `curl 127.0.0.1:8080/users | jq` **Expected Output :**  ### Step 6 : Add a parameter to the simple REST service **Step 6a : Finally, let's modify the /users endpoint to retrieve a specific user.** `Open demo/src/main/java/com/example/demo/DemoApplication.java` We'll add a @RequestParam annotation to our endpoint as shown in this code. We will also modify the query. If the name parameter is present, we add a WHERE clause with the name. `package com.example.demo; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.*; import org.springframework.web.bind.annotation.*; import com.datastax.oss.driver.api.core.CqlSession; import com.datastax.oss.driver.api.core.cql.*; import com.google.gson.Gson; import java.util.*; @RestController @EnableAutoConfiguration public class DemoApplication { @RequestMapping("/hello") String hello(@RequestParam(value = "name", defaultValue = "World") String name) { return String.format("Hello %s!\n", name); } @RequestMapping("/users") String users(@RequestParam(value = "name", defaultValue = "") String name) { ArrayList> results = new ArrayList>(); String result = ""; try (CqlSession session = CqlSession.builder().build()) { String query = "select * from user_management.user_credentials"; if (name.length() > 0) { query += " where username = '" + name + "'"; } ResultSet rs = session.execute(query); result = "["; for (Row row: rs) { HashMap record = new HashMap(); record.put("username", row.getString("username")); record.put("password", row.getString("password")); results.add(record); } } Gson g = new Gson(); return g.toJson(results); } @RequestMapping("/") String home() { return "Home\n"; } public static void main(String[] args) { SpringApplication.run(DemoApplication.class, args); } }` **Step 6b : Restart the server and wait for it to initialize.** `# Sending a Ctrl-C and restarting the server mvn spring-boot:run` **Step 6c : We can try the default behavior for the /users endpoint to retrieve all users.** `curl 127.0.0.1:8080/users | jq` **Expected Output :**  **Step 6d: let's test the endpoint with a parameter to retrieve a single user.** `curl 127.0.0.1:8080/users?name=User1 | jq` **Expected Output :** 

[SonicDMG]

Hey there Vaibhav, thank you for your submission. Nice job getting the app correctly configured and deployed. The only thing we are missing is step 2 of the homework.

2. Learn more about spring in the course and complete scenario Build a Spring Boot REST Service at the bottom of the page and make a screenshot of the "congratulations" page.

Please post an image of the "completed" screen once finished.