Spring RESTful Routing & Static Files

Spring RequestMapping

the annotation is used to map web requests to Spring Controller methods.

@RequestMapping Basics

• @RequestMapping — by Path

@RequestMapping(value = "/ex/foos", method = RequestMethod.GET)
@ResponseBody
public String getFoosBySimplePath() {
    return "Get some Foos";
}

• @RequestMapping — the HTTP Method
  •The HTTP method parameter has no default. So, if we don’t specify a value, it’s going to map to any HTTP request.

RequestMapping and HTTP Headers

• @RequestMapping With the headers Attribute
  when request mapping you can even specify the header for the request in the annotation attributes, and also multiple headers not only one.
  @RequestMapping(value = "/ex/foos", headers = { "key1=val1", "key2=val2" }, method = GET)
  • in the curl syntax to seperate between the header key and a value usually we use a : but in spring the = is used.

• @RequestMapping Consumes and Produces
  We can map a request based on its Accept header via the @RequestMapping headers attribute
  @RequestMapping(value = "/ex/foos", method = GET, headers = "Accept=application/json")

@RequestMapping(
  value = "/ex/foos", 
  method = RequestMethod.GET, 
  produces = "application/json"
)

•if you used the old type of mapping with the headers attribute it will be converted to the new procedures way
procedures supports multiple values

RequestMapping With Path Variables

mapping URI can be bound to variables via the @PathVariable annotation.

• Single @PathVariable If the name of the method parameter matches the name of the path variable exactly, then this can be simplified by using @PathVariable with no value and if it doesnt you have to use a value.

• Multiple @PathVariable

@RequestMapping(value = "/ex/foos/{fooid}/bar/{barid}", method = GET)
@ResponseBody
public String getFoosBySimplePathWithPathVariables
  (@PathVariable long fooid, @PathVariable long barid) {
    return "Get a specific Bar with id=" + barid + 
      " from a Foo with id=" + fooid;
}

• @PathVariable With Regex

RequestMapping With Request Parameters

@RequestMapping(value = "/ex/bars", method = GET)
@ResponseBody
public String getBarBySimplePathWithRequestParam(
  @RequestParam("id") long id) {
    return "Get a specific Bar with id=" + id;
}

extracting the value of the id parameter using the @RequestParam(“id”) annotation in the controller method signature.

To send a request with the id parameter, we’ll use the parameter support in curl

RequestMapping Corner Cases

New Request Mapping Shortcuts

• @GetMapping
• @PostMapping
• @PutMapping
• @DeleteMapping
• @PatchMapping

Accessing Data with JPA

Define a Simple Entity

create a class and annotate it with @Entity , indicating that it is a JPA entity, you store objects, each annotated as a JPA entity.

Create Simple Queries

Spring Data JPA focuses on using JPA to store data in a relational database. Its most compelling feature is the ability to create repository implementations automatically, at runtime, from a repository interface.

Create an Application Class

Spring Initializr creates a simple class for the application.
Now you need to modify the simple class that the Initializr created for you. To get output to the console

CrudRepository, JpaRepository, and PagingAndSortingRepository in Spring Data

JpaRepository – which extends PagingAndSortingRepository and the CrudRepository.

• CrudRepository provides CRUD functions
• PagingAndSortingRepository provides methods to do pagination and sort records
• JpaRepository provides JPA related methods such as flushing the persistence context and delete records in a batch • the JpaRepository contains the full API of CrudRepository and PagingAndSortingRepository because the inheritance.

CrudRepository

CRUD functionality:

• save(…) – save an Iterable of entities. so you can pass multiple objects to save them in a batch
• findOne(…) – get a single entity based on passed primary key value
• findAll() – get an Iterable of all available entities in database
• count() – return the count of total entities in a table
• delete(…) – delete an entity based on the passed object
• exists(…) – verify if an entity exists based on the passed primary key value

PagingAndSortingRepository

When using Pageable, we create a Pageable object with certain properties and we’ve to specify at least:

1. Page size
2. Current page number
3. Sorting

JpaRepository

JPA methods:

• findAll() – get a List of all available entities in database
• findAll(…) – get a List of all available entities and sort them using the provided condition
• save(…) – save an Iterable of entities. Here, we can pass multiple objects to save them in a batch
• flush() – flush all pending task to the database
• saveAndFlush(…) – save the entity and flush changes immediately
• deleteInBatch(…) – delete an Iterable of entities. Here, we can pass multiple objects to delete them in a batch