celularfreak/lab-java-intro-to-spring-boot

LAB Java | Intro to Spring Boot

Introduction

We have just learned how to create GET as well as how to handle query parameters and path variables in the GET requests so let's practice a bit more.

Requirements

1. Fork this repo.
2. Clone this repo.
3. Add your instructor and the class graders as collaborators to your repository. If you are unsure who your class graders are, ask your instructor or refer to the day 1 slide deck.
4. In the repository, create a Java project and add the code for the following prompts.

Submission

Once you finish the assignment, submit a URL link to your repository or your pull request in the field below.

Set up

For this lab, you will need to create two database tables and seed them with some sample data. The database data represents mock clients for a multi-city hospital.

Employee Table

employee_id	department	name	status
356712	cardiology	Alonso Flores	ON_CALL
564134	immunology	Sam Ortega	ON
761527	cardiology	German Ruiz	OFF
166552	pulmonary	Maria Lin	ON
156545	orthopaedic	Paolo Rodriguez	ON_CALL
172456	psychiatric	John Paul Armes	OFF

Note that admitted_by is a foreign key to the employee table.

Patient Table

patient_id	name	date_of_birth	admitted_by
1	Jaime Jordan	1984-03-02	564134
2	Marian Garcia	1972-01-12	564134
3	Julia Dusterdieck	1954-06-11	356712
4	Steve McDuck	1931-11-10	761527
5	Marian Garcia	1999-02-15	172456

Instructions

1. Get all doctors: Create a route to get all doctors.
2. Get doctor by ID: Create a route to get a doctor by employee_id.
3. Get doctors by status: Create a route to get doctors by status.
4. Get doctors by department: Create a route to get doctors by department.
5. Get all patients: Create a route to get all patients.
6. Get patient by ID: Create a route to get a patient by patient_id.
7. Get patients by date of birth range: Create a route to get patients date of birth within a specified range.
8. Get patients by admitting doctor's department: Create a route to get patients by the department that their admitting doctor is in (For example, get all patients admitted by a doctor in cardiology).
9. Get all patients with a doctor whose status is OFF: Create a route to get all patients with a doctor whose status is OFF.

FAQs

I am stuck and don't know how to solve the problem or where to start. What should I do?

If you are stuck in your code and don't know how to solve the problem or where to start, you should take a step back and try to form a clear, straight forward question about the specific issue you are facing. The process you will go through while trying to define this question, will help you narrow down the problem and come up with potential solutions.

For example, are you facing a problem because you don't understand the concept or are you receiving an error message that you don't know how to fix? It is usually helpful to try to state the problem as clearly as possible, including any error messages you are receiving. This can help you communicate the issue to others and potentially get help from classmates or online resources.

Once you have a clear understanding of the problem, you should be able to start working toward the solution.

How do I create a Spring boot project?

Spring boot is a framework for creating stand-alone, production-grade applications that are easy to launch and run. The best way to create a Spring boot project is to use the Spring Initializer website. The website provides a convenient way to generate a basic project structure with all the necessary dependencies and configurations.

• Step 1: Go to start.spring.io
• Step 2: Choose the type of project you want to create, such as Maven or Gradle.
• Step 3: Select the version of Spring Boot you want to use.
• Step 4: Choose the dependencies you need for your project. Some common dependencies include web, jpa and data-jpa.
• Step 5: Click the "Generate" button to download the project files.

Alternatively, you can use an Integrated Development Environment (IDE) such as Eclipse or IntelliJ IDEA. These IDEs have plugins for creating Spring boot projects, making it easy to set up the environment and get started with coding.

What is JPA and how can I use it in Java?

JPA stands for Java Persistence API, which is a Java specification for accessing, persisting and managing data between Java objects and a relational database. JPA provides a standard interface for accessing databases, reducing the need for custom data access code and enabling efficient management of database connections.

To use JPA in Java, you will need to include the necessary dependencies in your project, such as the Hibernate JPA implementation and create entity classes to represent your data. These entity classes will be annotated with JPA-specific annotations, such as @Entity and @Id, to indicate the mapping between the Java class and the database table.

Here is a code snippet to show you how to create a JPA entity class in Java:

@Entity
public class Employee {
   @Id
   @GeneratedValue(strategy=GenerationType.IDENTITY)
   private int id;

   private String name;
   private int age;
   private String position;

   // Getters and Setters for the attributes
}

What is the purpose of using the "@Entity", "@Table" and "@Column" annotations in JPA (Java Persistence API)?

The @Entity, @Table and @Column annotations in JPA (Java Persistence API) are used to map Java objects to relational database tables.

@Entity is used to mark a class as a persistent entity. This means that instances of the class can be stored in a database.

@Table is used to define the name of the database table that the entity will be mapped to.

@Column is used to define the columns in the table that correspond to the attributes of the entity.

Here is an example of how to use these annotations:

@Entity
@Table(name="employee")
public class Employee {

  @Id
  @GeneratedValue(strategy=GenerationType.AUTO)
  @Column(name="id")
  private int id;

  @Column(name="first_name")
  private String firstName;

  @Column(name="last_name")
  private String lastName;

  //getters and setters
}

In this example, the Employee class is marked as a persistent entity using the @Entity annotation. The name of the database table is defined using the @Table annotation as "employee". The id, firstName and lastName attributes are mapped to columns in the "employee" table using the @Column annotation.

What is the purpose of using the "@RestController", "@GetMapping" and "@ResponseStatus" annotations in Java for building a RESTful web service?

The @RestController annotation is used in Java to define a class as a RESTful web service controller. This annotation allows the class to handle HTTP requests and return HTTP responses.

The @GetMapping annotation is used to map a specific HTTP GET request to a method in a controller class. This allows the method to handle the request and return a response.

The @ResponseStatus annotation is used to set the HTTP status code for the response returned by a method in a controller class.

Here's a code snippet showing how to use these annotations in Java:

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.ResponseStatus;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.http.HttpStatus;

@RestController
public class ExampleController {

  @GetMapping("/example")
  @ResponseStatus(HttpStatus.OK)
  public String exampleMethod() {
    return "This is a response from a RESTful web service";
  }
}

In this example, the ExampleController class is defined as a RESTful web service controller using the @RestController annotation. The exampleMethod is mapped to a specific HTTP GET request using the @GetMapping("/example") annotation and the HTTP status code for the response is set to HTTP 200 OK using the @ResponseStatus(HttpStatus.OK) annotation.

What is the purpose of "@JsonIgnore" in Java and how is it used?

The @JsonIgnore annotation is used in Jackson (a popular library for JSON processing) to ignore a property when serializing or deserializing an object to/from JSON. This means that when the object is converted to JSON, the property marked with @JsonIgnore will not be included in the JSON representation.

The @JsonIgnore annotation is applied to a property in a Java class to ignore it during JSON serialization or deserialization. For example, consider a class named Employee with a property named "password". To ignore the "password" property, we can annotate it with @JsonIgnore:

public class Employee {
  private String name;
  private int age;
  @JsonIgnore
  private String password;

  // getters and setters for the properties
}

When this class is serialized to JSON, the "password" property will not be included in the JSON representation.

What is "JpaRepository" and how can I use it in Java?

JpaRepository is a Spring Data interface that extends the PagingAndSortingRepository interface. It provides all the basic CRUD (Create, Read, Update, Delete) operations and additional methods to work with JPA (Java Persistence API) to interact with the database.

To use JpaRepository in your project, follow the below steps:

Step 1: Import the necessary libraries

import org.springframework.data.jpa.repository.JpaRepository;

Step 2: Create an interface that extends JpaRepository

public interface MyRepository extends JpaRepository<MyEntity, Long> {

}

Note: In the above code, MyEntity is the entity class that you want to interact with the database and Long is the type of the primary key of MyEntity.

Step 3: Inject the interface in the class where you want to use it.

@Autowired
private MyRepository myRepository;

Step 4: You can now use the methods provided by JpaRepository to interact with the database, for example:

MyEntity myEntity = new MyEntity();
myRepository.save(myEntity);

With the above steps, you can now use JpaRepository to interact with the database in your Java project.

What are derived query methods in JPA and how do I use them in Java?

Derived query methods in JPA are methods in a JPA repository that are automatically generated by the framework based on method names. These methods allow developers to perform common database operations such as finding entities based on specific criteria, sorting, pagination and more, without having to manually write the corresponding SQL query.

To use derived query methods in Java with JPA, follow these steps:

1. Create a JPA repository interface: To start, create an interface that extends JpaRepository and specifies the entity class and the primary key data type. For example:

```java
import org.springframework.data.jpa.repository.JpaRepository;
import org.example.domain.User;

public interface UserRepository extends JpaRepository<User, Long> {
}
```

2. Define the method name: Next, you can define the method name based on the query you want to perform. There are several conventions that JPA follows to determine the query to be executed, such as keywords such as findBy, readBy, queryBy, countBy and deleteBy, followed by the name of the entity’s properties. For example, to find all users with a specific first name, you can define the method name as follows:

```java
List<User> findByFirstName(String firstName);
```

3. Inject the repository: Finally, you can inject the repository into your service or component class and call the methods to perform the query operations.

```java
@Autowired
private UserRepository userRepository;

public List<User> getUsersByFirstName(String firstName) {
  return userRepository.findByFirstName(firstName);
}
```

Note: The exact implementation of derived query methods may vary depending on the JPA implementation you are using (e.g., Hibernate, EclipseLink, etc.). However, the basic concept of using method names to generate queries remains the same.

How can I use the JPA annotations "@OneToOne", "@OneToMany", "@ManyToOne", "@ManyToMany", "@JoinColumn" and "@JoinTable" in Java?

The Java Persistence API (JPA) provides several annotations for mapping relationships between entities in Java applications. These annotations include:

1. @OneToOne: This annotation is used to define a one-to-one relationship between two entities. The following code shows how to use the @OneToOne annotation:

@Entity
public class Employee {

  @Id
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  private Long id;

  private String name;

  @OneToOne(cascade = CascadeType.ALL)
  @JoinColumn(name = "address_id", referencedColumnName = "id")
  private Address address;

  // Getters and setters ...
}

@Entity
public class Address {

  @Id
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  private Long id;

  private String street;

  private String city;

  // Getters and setters ...
}

2. @OneToMany & @ManyToOne: These annotations are used to define one-to-many and many-to-one relationships between two entities.

The following code shows how to use the @OneToMany and the @ManyToOne annotation:

@Entity
public class Department {

  @Id
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  private Long id;

  private String name;

  @OneToMany(mappedBy = "department")
  private List<Employee> employees;

  // Getters and setters ...
}

@Entity
public class Employee {

  @Id
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  private Long id;

  private String name;

  @ManyToOne
  @JoinColumn(name = "department_id", referencedColumnName = "id")
  private Department department;

  // Getters and setters ...
}

3. @ManyToMany & @JoinColumn & @JoinTable: The @ManyToMany annotation is used in Java to define a many-to-many relationship between two entities. This means that multiple instances of one entity can be related to multiple instances of another entity.

The @JoinColumn annotation is used in Java to specify the foreign key column that will be used to join the two entities. The foreign key column is used to establish a relationship between the entities.

The @JoinTable annotation is used in Java to define a join table for a many-to-many relationship. The join table is used to store the relationship information between the two entities.

The following code shows how to use the @ManyToMany, @JoinColumn and @JoinTable annotations:

@Entity
public class User {

    @ManyToMany
    @JoinTable(name = "user_role",
    joinColumns = @JoinColumn(name = "user_id"),
    inverseJoinColumns = @JoinColumn(name = "role_id"))
    private List<Role> roles;

}

@Entity
public class Role {

    @ManyToMany(mappedBy = "roles")
    private List<User> users;

}

I am unable to push changes to my repository. What should I do?

If you are unable to push changes to your repository, here are a few steps that you can follow:

1. Check your internet connection: Ensure that your internet connection is stable and working.
2. Verify your repository URL: Make sure that you are using the correct repository URL to push your changes.
3. Check Git credentials: Ensure that your Git credentials are up-to-date and correct. You can check your credentials using the following command:

git config --list

4. Update your local repository: Before pushing changes, make sure that your local repository is up-to-date with the remote repository. You can update your local repository using the following command:

git fetch origin

5. Check for conflicts: If there are any conflicts between your local repository and the remote repository, resolve them before pushing changes.
6. Push changes: Once you have resolved any conflicts and updated your local repository, you can try pushing changes again using the following command:

git push origin <branch_name>