Configure JPA and Initialized Data

In the previous section, we have hardcoded the response for the exchange value. It comes from the database. In this section, we will create a connection to the in-memory database.

Let’s see how to connect microservice to the H2 database. Follow the following steps to connect microservice to JPA in-memory database.

Step 1: Open pom.xml of currency-exchange-service and add the following two dependencies.

  <dependency>  <groupId>com.h2database</groupId>  <artifactId>h2</artifactId>  <version>1.4.197</version>  <scope>test</scope>  </dependency>  <dependency>  <groupId>org.springframework.boot</groupId>  <artifactId>spring-boot-starter-data-jpa</artifactId>  <version>2.1.3.RELEASE</version>  </dependency>  

Once we have added the dependencies, now we have to define entity.

Step 2: Open the ExchangeValue.java file and do the following:

Add @Entity annotation at the class level.
Define the table name by using the annotation @Table.
Define an Id for the entity by adding the annotation @Id.
Define columns by adding the annotation @Column above each field and also specify the column name.

ExchangeValue.java

  package com.tutoraspire.microservices.currencyexchangeservice;  import java.math.BigDecimal;  import javax.persistence.Column;  import javax.persistence.Entity;  import javax.persistence.Id;  import javax.persistence.Table;  @Entity  @Table(name=”Exchange_Value”)  public class ExchangeValue   {  @Id  @Column(name=”id”)  private Long id;  @Column(name=”currency_from”)  private String from;  @Column(name=”currency_to”)  private String to;  @Column(name=”conversion_multiple”)  private BigDecimal conversionMultiple;  @Column(name=”port”)  private int port;  //default conatructor  public ExchangeValue()  {  }  //generating constructor using fields  public ExchangeValue(Long id, String from, String to, BigDecimal conversionMultiple)   {  super();  this.id = id;  this.from = from;  this.to = to;  this.conversionMultiple = conversionMultiple;  }  //generating getters and setters  public int getPort()   {  return port;  }  public void setPort(int port)   {  this.port = port;  }  public Long getId()   {  return id;  }  public String getFrom()   {  return from;  }  public String getTo()   {  return to;  }  public BigDecimal getConversionMultiple()   {  return conversionMultiple;  }  }  

We have created the entity, now we have to insert some data into the database.

Step 3: Create a data.sql file to insert data into database.

Right-click on the folder src/main/resources -> New -> File -> Provide the name data.sql -> Finish

Step 4: Insert the data into data.sql file. We have inserted the following data:

data.sql

  insert into exchange_value(id,currency_from,currency_to,conversion_multiple,port)  values(10001,’USD’, ‘INR’ ,65,0);  insert into exchange_value(id,currency_from,currency_to,conversion_multiple,port)  values(10002,’EUR’, ‘INR’ ,75,0);  insert into exchange_value(id,currency_from,currency_to,conversion_multiple,port)  values(10003,’AUD’, ‘INR’ ,25,0);  

Step 5: Open application.properties file and enable H2 console, configure URL and datasource. The default JDBC URL is testdb. We can specify our own JDBC URL.

We have specified JDBS URL: jdbc:h2:mem:tutoraspire

application.properties

  spring.application.name=currency-exchange-service  server.port=8000  spring.jpa.show-sql=true  spring.h2.console.enabled=true  spring.datasource.platform=h2  spring.datasource.url=jdbc:h2:mem:tutoraspire  

Step 6: Restart the application.

Step 7: Open the browser and type the URI http://localhost:8000/currency-exchange/from/USD/to/INR. It returns the response, as shown below: