Resttemplate pagination

Are you tired of writing tests which have a lot of boilerplate code? Spring Batch has a good support for reading input data from different data sources such as files and databases.

This means that we have to create a custom ItemReader. This blog post describes how we can create a custom ItemReader that reads the input data of our batch job by using the RestTemplate class. During this tutorial we will implement several Spring Batch jobs that processes the student information of an online course.

The StudentDTO class contains the information of a single student, and its source code looks as follows:. Before we can use our new ItemReaderwe have to configure the RestTemplate bean. If we use Spring Framework, the source code of our application context configuration class looks as follows:. The source code of this class looks as follows:. After we have configured the RestTemplate bean, we can finally configure our new ItemReader bean.

The next part of this tutorial describes how we can read the input data of our batch job from an Excel spreadsheet.

Pagination with Spring Rest and Angular 5/4

You can get the example applications of this blog post from Github: Spring example and Spring Boot example. I am struggling with the best way to unit test it though.

Do you have any suggestions or additions for this example? You could move the logic that reads the input data to a separate component I will call this component RestInputReader and inject that component to the Spring Batch reader. This gives you the possibility to replace the RestInputReader with a stub when you are writing unit tests for the Spring Batch reader. I would test it by writing integration tests. Can you let me know after implementing this code, how do we execute this?

Are you implementing a tasklet? Good catch. I guess that I simply forgot to change the name of the method after I copied it from another launcher class. It is very useful. Can please let me know how to run this project? Unfortunately I cannot cover this topic in a single answer. However, you can find my Spring Batch tutorial and a few other great resources from my Spring Batch resource page. Also, this blog post explains how you can read data from XML file and write it to a database.

Hi Petri, Thank you for this great post. I have approximately the same use case than you. But my problem is than my rest service is using a database containing more than So I am afraid than my memory is not big enough. How can I handle that problem?The solution posted didn't work for me, because the total elements were not set correctly.

I implemented the Page with a delegate pattern, which worked for me. Here's the working code:. When migrating from Spring Boot 1. Pageproblem : abstract types either need to be mapped to concrete typeshave custom deserializeror be instantiated with additional type information at [ Source : java.

PushbackInputStream 3be1e1f2 ; line : 1column : 1 ]; nested exception is com.

Spring – RestTemplate

JsonMappingException : Can not construct instance of org. Pageproblem : abstract types either need to be mapped to concrete typeshave custom deserializeror be instantiated with additional type information Thank you in advance. ArrayList ; import java.

List ; import org. PageImpl ; import org. Expanding on above, but without the need to implement every property.

JsonCreator ; import com. JsonProperty ; import org. PageRequest ; import org. Pageable ; import java. Solution in Kotlin import com. JsonCreator import com.

JsonProperty import com. JsonNode import org. PageImpl import org. PageRequest import org. Pageable import java. JsonProperty ; import com.

JsonNode ; import org. Here's the working code: import org. Converter ; import org.Comment 1. This article will focus on the implementation of pagination in a RESTful web service. The first question when designing pagination in the context of a RESTful architecture is whether to consider the page an actual resource or just a representation of resources.

Treating the page itself as a resource introduces a host of problems such as no longer being able to uniquely identify resources between calls. This, coupled with the fact that outside the RESTful context, the page cannot be considered a proper entity, but a holder that is constructed when needed makes the choice straightforward: the page is part of the representation.

The next question in the pagination design in the context of REST is where to include the paging information:. Keeping in mind that a page is not a resourceencoding the page information in the URI is no longer an option. This approach does however have one downside — it cuts into the query space for actual queries:. The two query parameters are defined in the request mapping and injected into the controller method via RequestParam ; the HTTP response and the Spring UriComponentsBuilder are injected in the Controller method to be included in the event, as both will be needed to implement discoverability.

In REST, Discoverability is a cross cutting concernapplicable not only to specific operations but to types of operations. For example, each time a Resource is created, the URI of that resource should be discoverable by the client.

Since this requirement is relevant for the creation of ANY Resource, it should be dealt with separately and decoupled from the main Controller flow. With Spring, this decoupling is achieved with eventsas was thoroughly discussed in the previous article focusing on Discoverability of a RESTful service.

In the case of pagination, the event — PaginatedResultsRetrievedEvent — was fired in the Controller, and discoverability is achieved in a listener for this event:. In short, the listener logic checks if the navigation allows for a next, previous, first and last pages and, if it does, adds the relevant URIs to the Link HTTP Header. This is the single responsibility of the listener the full code here. Both the main logic of pagination and discoverability should be extensively covered by small, focused integration tests; as in the previous articlethe rest-assured library is used to consume the REST service and to verify the results.

These are a few example of pagination integration tests; for a full test suite, check out the github project link at the end of the article :. Testing Discoverability of Pagination is relatively straightforward, although there is a lot of ground to cover.

The tests are focused on the position of the current page in navigation and the different URIs that should be discoverable from each position:. On the same topic of pagination and discoverability, the choice must be made if a client is allowed to retrieve all the Resources in the system at once, or if the client MUST ask for them paginated.

If the choice is made that the client cannot retrieve all Resources with a single request, and pagination is not optional but required, then several options are available for the response to a get all request.

resttemplate pagination

One option is to return a Not Found and use the Link header to make the first page discoverable:. Another option is to return redirect — See Other — to the first page of the pagination. One view on this approach is that the HTTP Range extensions were not intended for pagination, and that they should be managed by the Server, not by the Application. Implementing pagination based on the HTTP Range header extensions is nevertheless technically possible, although not nearly as common as the implementation discussed in this article.

This article covered the implementation of Pagination in a RESTful service with Spring, discussing how to implement and test Discoverability. For a full implementation of pagination, check out the github project.

Integration Zone. Over a million developers have joined DZone. Let's be friends:. DZone 's Guide to. Free Resource. Like 4.Are you tired of writing tests which have a lot of boilerplate code? We have also implemented a search function that ignores case and returns todo entries whose title or description contains the given search term. This search function sorts the returned todo entries in ascending order by using the title of the returned todo entry.

It returns all todo entries that are found from the database, and this is a performance problem. If you are not familiar with Spring Data JPA, you should read the following blog posts before you continue reading this blog post:. If we want create the Pageable object manually, the service class or other component that wants to paginate the query results, which are returned by a Spring Data JPA repository, must create the Pageable object and pass it forward to the invoked repository method.

The source code of the RepositoryTodoSearchService class, which uses this method, looks as follows:. The following examples demonstrate how we can implement the private createPageRequest method:. Example 1: If we want to get the first page by using page size 10, we have to create the Pageable object by using the following code:.

Example 2: We have to sort the query results in ascending order by using the values of the title and description fields. If we want to get the second page by using page size 10, we have to create the Pageable object by using the following code:. Example 3: We have to sort the query results in descending order by using the value of the description field and in ascending order by using the value of the title field. We can enable Spring Data web support by annotating our application context configuration class with the EnableSpringDataWebSupport annotation.

The relevant part of the PersistenceContext class, which configures the persistence layer of our example application, looks as follows:. This registers two HandlerMethodArgumentResolver objects that are described in the following:. We can now specify the information of the requested page and configure the sorting options of the invoked database query by setting the values of the following request parameters:.

After we have enabled Spring Data web support, we can inject Pageable objects into controller handler methods. The source code of the TodoSearchController class, which utilizes Spring Data web support, looks as follows:.

The RepositoryTodoSearchService class implements the TodoSearchService interface, and its findBySearchTerm method simply passes the search term and the Pageable object forward to the invoked repository method.

resttemplate pagination

After we have created the Pageable object manually or obtained it by using Spring Data web support, we have to create the database query that paginates its query results by using the Pageable object. If we want to paginate all entities found from the database, we can use one of the following methods:.

Firstif we created our repository interface by extending the CrudRepository interface, we have to modify it to extend only the PagingAndSortingRepository interface. The PagingAndSortingRepository interface declares one method which we can use when we want to paginate the query results of a query that fetches all entities from the database:.

If we create our database queries from the method name of our query methodwe can paginate the query results by following these steps:. Because the search function of our example application is case-insensitive and it returns todo entries whose title or description contains the given search term, the source code of our repository interface looks as follows:. We can paginate the query results of named queries that use JPQL by following these steps:. If we want to paginate the query results of the named query called: Todo.

If we create our JPQL queries by using the Query annotationwe can paginate the query results by following these steps:. This interface declares one method that we can use when we want to paginate the query results of JPA criteria queries:. The source code of the RepositoryTodoSearchService class, which paginates our query results by using the Pageable object, looks as follows:. This interface declares one method that we can use when we want to paginate the query results of database queries that use Querydsl:.

The next part of this tutorial describes how we can add the creation and modification time fields into our entities by using the auditing infrastructure of Spring Data JPA.

It explains how you can automatically resolve the Pageable argument by passing specific request parameters to the request. At first I thought of updating my example application, but after giving it some thought, I decided to leave it as an exercise for the reader.

Have you removed H2 database dependency from the pom. If you have done this and are still having problems, please let me know what the exact problem is. Hi Petri, I run your example with Maven. I do not see nowhere the pagination even I created manually 22 persons. If your tutorial application is coded to see 10 persons per page, I have to see a link to go to the second page because i have 22 persons.JSONObject from org. All examples below are for JSON, as it is my personal favorite out of the two we offer.

I encourage you to install Groovy to be able to try out a few examples. When the above script is launched, all required dependencies and the spring-web artifact will automatically be downloaded and added to the classpath.

Making a simple GET request is then pretty simple. The second parameter specifies the Type that we expect back from the method call, the return type. Here, we use a very simple Type — String — which is a default type of the RestTemplate.

Especially in statically typed programming languages, such as Java, this is a nice feature as it allows you to use code completion to figure out what the response is made of — instead of inspecting the low-level JSON response.

The first thing you should notice when you compare the two snippets is: the second one is way longer. This is mostly due to the fact that we now need to have the Model classes in our classpath — and although we ignore some elements of the JSON Response via. Things get a bit tricky though, when optimizations are applied, like not serializing some properties or changing the names. For the purpose of this example, I just created a few classes as Groovy makes this trivial, too.

Adding this converter to the default converters is simple:. The first line in the above code snipped creates a fresh RestTemplate. The second line accesses the list of message converters and adds the MappingJacksonHttpMessageConverter to it. If you wonder what converters are installed by default, here we go. And we then simply iterator over the products list and print the product names.

Aug RestTemplate import groovy. RestTemplate import org.A family guy with fun loving nature. Love computers, programming and solving everyday problems.

Find me on Facebook and Twitter. HiI was hitting urlWhat i noticed is that i am not getting response body in restTemplate.

But the same data i am passing through postmani am able to get response body. Can you give any suggestion on what could be the reason. RestTemplate usage is explained only for endpoint URI with the default port Thanks in advance. I am trying to call a third party api gateway from my server using RestTemplate. Please have a look at the below link. Any leads will be appreciated. I tried using the restTemplate.

I know the json I am passing in is working because I can use swagger and get successes, but when I use RestTemplate, I am getting error media type.

So is there something I need to inject or setup with the RestTemplate before I can run it? Your tutorials are really very helpful……Can you please let me know how can we use OAuth 2. But whenever i am trying to access this url by passing name parameter I am getting Error. Please suggest what could be the problem. I have tried all possible ways. Your tutorials are very nice and I follow them regularly.

I have an issue that when I access your site from my iPad, the right most part of code samples is getting truncated and there is no scroll bar to view the entire line.

Spring REST Client with RestTemplate: Consume RESTful Web Service Example for XML and JSON

Can you please verify this on iPad and adjust the width of the frames accordingly? Lokesh, please ignore my earlier comment and scrolling is working for me?. Using deleteEmployee was little confusing. How can I call a Restful webservice through a Spring client when the actual webservice is developed in Jersey framework. I am specifically looking to call post webservice through a Json object as input. How to consume response body in case of response code like Lets say I made call with resttemplate and it returned and response contains body with reason …right now its throwing exception — HttpClientErrorException — and http converters are no executed….

I goggled lot to find the solution, but did not find any working example.Spring is a popular Java application framework and Spring Boot is an evolution of Spring that helps create stand-alone, production-grade Spring based applications easily. Since Spring 5. In the future releases, RestTemplate will be deprecated in favour of WebClient.

We initialize a Node projet and install json-serverfakerand fs modules. The json-server is used to create a test JSON server, faker to generate test data, and fs to work with filesystem in JavaScript.

With faker we generate one hundred users with id, first name, last name, and email attributes. The data is written to data. The file is used by json-server. We start the json-server. We create a Spring Boot application.

resttemplate pagination

We need the following Maven dependencies and plugins: spring-boot-starterspring-webjackson-databindspring-boot-starter-testand spring-boot-maven-plugin. The application. We turn off the Spring banner, set the logging level to info, and set the console logging pattern. We also set an URL property which points to the users resource. The property is going to be later retrieved with Value. We create a configuration bean. It sets up the RestTemplate. It fetches all users from the JSON test server.

We use the getForObject method to generate the request. Since we expect an array of objects, we use User[]. MyRunner uses the MyRestService to get the users. We show first ten users to the console. We test the getUsers service method. We test that the JSON data is not empty and that it contains one hundred elements. The RestClientTest annotation is used to test Spring rest clients.

It disables full auto-configuration and applies only configuration relevant to rest client tests. In this tutorial, we have shown how to use RestTemplate to create synchronous requests in a Spring application.

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