Apache POI Insert Line Break In Excel Cell Data

Introduction Here I am going to show you how to insert line break in excel cell data using Apache POI in Java language. There may be requirements where you need to write long text in a cell or in multiple cells of excel file, but the long text is not fit within the view port or screen of the device;…

Spring Boot Data JPA Entity DTO Mapping Using MapStruct

Introduction In this example I will show you how to convert entity class to DTO (Data Transfer Object) class and DTO class to entity class using MapStruct. So, MapStruct will map entity class to DTO class or vice versa. This example will test both from RESTful webservices and standalone main class. Spring Boot provides CommandLineRunner interface to run the project…

Spring Boot REST API MultiValueMap Example

MultiValueMap In this example I am going to show you how to use Spring’s MultiValueMap in REST API. This MultiValueMap is similar to the Jersey’s MultivaluedMap. A MultiValueMap<K, V> or MultivaluedMap<K, V> is a map of key-values pairs. Each key can have zero or more values, where K – the type of keys maintained by this map and V – the type of mapped values. This…

Spring Boot Filters Example

Introduction Servlet filters are Java classes that are invoked at pre and post processing of requests. So filters are used to intercept requests from clients before they access requests at backend (server). to manipulate responses from server before they are sent back to the client RequestContextFilter is also a servlet filter that extends OncePerRequestFilter that extends GenericFilterBean which implements servlet…

PreAuthorize HasPermission Security Using Spring Boot Data JPA

Introduction The ability of hasPermission() method in Spring Boot Security applications is to determine the accessibility of a particular user for the application. The permission of an access can be read, write, etc. So, a particular user has defined set of access permission by which a user can perform certain activities in the application. The most useful annotation @PreAuthorize, which…

Changing Context Path Of Web Application In Tomcat Server

Introduction Here I am going to show you how to change context path of web application in Tomcat server. So, basically web applications are deployed into Tomcat server and meaningful, memorable context paths are assigned for web applications. Even if you do not want to set any context path for an application, you can do so. For every web application…

Convert Date From One Format To Another Format In Java

Introduction In this example I am going to show you how to convert date from one format to another format in Java programming language. There are many situations where you need to convert date format in your Java based application from one format to another format. You can use prior to Java 8 and Java 8 onward ways to convert…

Error bean securityConfig: unresolvable circular reference

Problem Recently while I was working with Spring Security in recent versions of Spring Boot framework (2.6.6/2.6.7), I was getting the following error (Requested bean is currently in creation: Is there an unresolvable circular reference?):

How To Create Users In Tomcat Server

Introduction Here I am going to show you how to create users in Tomcat server to manage applications, server status, etc. When you deploy application into Tomcat server, generally you put the war archive files under webapps folder of the Tomcat server. You can easily access the application once it is successfully deployed through its context path of the application….

Write Or Append To A File Using Java

Introduction In this short example code I will show you how to create a new file for writing into it or if the file already exists then append to it instead of creating a new file using Java programming language. If you have a requirement that either you need to log some data into an existing file or create a…