How to mask a Field or an Attribute in Java

Here I am going to show you how to mask a field or an attribute in Java programming language. This kind of situation occurs when you are dealing with mainly debit or credit cards. So you have a POJO or model class for your card (debit or credit) but for security reason you do not want to display the card number, then you need to mask the card number. Masking something means you want to replace the actual value with some other value, for example, your card number is 3456…

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Junit 5 Mockito Verify Example

In this example I am going to show you how to verify a method has been executed at least. Why do you need to verify method execution? Consider the void method, in your Java class, which you want to perform Junit test case on it and you don’t have any way to tell whether your method successfully tested or not. So here you are left with only one option, i.e., to check whether your method was executed or not. If your method was executed then you know that your code…

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Junit 5 Expected Exception using Assertions.assertThrows()

This example will show you how to work with expected exception using Junit 5 Assertions.assetThrows(). Junit 4 (at least 4.7 version) provides expected attribute with @Test annotation, where you can mention what exception you are expecting from your test method but Junit 5 does not provide such thing. Junit 5 provides assertThrows() that can be used to check the expected exception. A Java unit test should verify correct exception thrown in exceptional case and no exception should be thrown in normal case. assertThrows() asserts that execution of the supplied executable…

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Mock an Autowired Value Field in Spring with Junit 5

In this example I am going to show you how to mock an autowired field in Spring boot framework with Junit 5. When you use @Value annotation in Spring beans to read the value from properties file and later when you want to perform Junit test then you also need to pass value for this autowired field value otherwise you won’t be able to cover your testing. Read if you need Junit 4 version of testing for Spring’s autowired field value. Now it is really cumbersome to place a properties…

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Parallelism Example in Java Stream API

I am going to show you how to work with parallel stream in Java 8 or higher version of Java. In parallel computing a task is divided into sub-tasks and these sub-tasks are computed parallelly in each separate threads and finally the result of the solution for each sub-tasks is combined. One of the features for computing parallelism is to use Java’s join/fork framework, where you need to mention how the particular task will be sub-divided or partitioned into sub-tasks. The main difficulty for parallel computing in applications is the…

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How to pretty print JSON in Java

Here I am going to show you how to pretty print JSON in Java. I am going to use here JSON, Jackson and Google Gson library to prettify the JSON. I am also going to show you how to read and write JSON file using Java 8 or later version. I am going to show you how to prettify JSON string as well as JSON file data. Why do you need to prettify the JSON data? Because you want to read this JSON data manually when you received this data…

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How to generate PDF report from MySQL database in Spring Boot

I am going to show yo how to download PDF file from MySQL database using Spring Boot and iText library in Java programming language. Many applications require dynamic generation of PDF documents for reporting purpose, such as, generating statements for customers, readers buying online specific chapters of a book, etc. In my another tutorial I had shown how to create or write to a PDF file using Java based iText library. The iText library is freely available and can be used using maven or gradle build tool. We can also…

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How to convert PDF File to CSV File using iText API in Java

In this example I going to show you how to convert PDF file to CSV file. I will read the PDF file using iText library and write data to the CSV file using Java programming language. In my previous example I had shown how to convert CSV file to PDF file using iText library. As you know that CSV is a comma separated value, so I assume that the PDF file is having data in tabular format which would be converted into comma separated values. Related Posts: How to generate…

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How to convert CSV file to PDF file using iText API in Java

Here I am going to tell you how to convert CSV to PDF file using iText library in Java programming language. I am going to use Java 7 or later version’s new feature Path API to read the CSV file and Java 8’s Stream API to split the comma separated line or record. I am going to show you how to read file content into byte array and how to convert byte array into String. Then I am converting the array of String into a list of String. Finally from…

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Junit Testing for Multiple Files Upload Spring REST Controller

Introduction Here I am going to write Junit test case for testing multiple files upload in Spring REST Controller. I have already created how to upload multiple files using Spring REST API and I also had shown how to test it through REST client tool – Postman. In this tutorial I am going to use Junit 5, @WebMvcTest annotation to test the multiple files upload REST API. @WebMvcTest annotation can be used not only to test Spring Controllers but also Spring REST Controllers. I will build the applications using both maven…

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