Apache Common Collections framework provide a new map collection called “BidiMap”. This collection is similar to map and at the same time it is different. Similarities 1) Both will contain list of entries each of key value pair 2) By using key we can retrieve the corresponding value Differences 1) In BidiMap we can invert…… Continue reading BidiMap Example
Bag Collection
A bag or multiset is a collection that allow duplicate items. It also keeps count of how many duplicate items are present. Apache Collections framework provide an implementation of Bag collection. Below is an example of it. Bag example 1 import org.apache.commons.collections4.Bag; 2 import org.apache.commons.collections4.bag.HashBag; 3 4 public class Example1 { 5 public static void…… Continue reading Bag Collection
FlatFileHeaderCallback and FlatFileFooterCallback example
In this post I will explain how to add header and footer to the destination file created by Spring batch. When Spring batch transfer records from source to destination file in batch, it provides facility through which the programmer can provide header and footer information thathas to added in the destination file. To take advantage…… Continue reading FlatFileHeaderCallback and FlatFileFooterCallback example
Custom FieldSetMapper example
In the previous post “Spring Batch Simple Example” we used “BeanWrapperFieldSetMapper” while reading the employee records from the file. The BeanWrapperFieldSetMapper created a newinstance of Employee class for every employee record in the file and set the instance fields. We can have more control on the task performed by BeanWrapperFieldSetMapper by providing a custom implementation…… Continue reading Custom FieldSetMapper example
Spring Batch Simple Example Part 3
In this post I will explain how to combine the reader and writer in a job and how to run the job. We define a job which will transfer the employee records from one file to another file in batches. <batch:job id=”importEmployees”> <batch:step id=”readWriteEmployees”> <batch:tasklet> <batch:chunk reader=”reader” writer=”writer” commit-interval=”50″/> </batch:tasklet> </batch:step> </batch:job> <bean id=”transactionManager” class=”org.springframework.jdbc.datasource.DataSourceTransactionManager”>…… Continue reading Spring Batch Simple Example Part 3
Spring Batch Simple Example Part 2
In this post, I will explain how to write the employee objects created in the reading process to a file. To write the list of employee records in batches, we need to create an instance of org.springframework.batch.item.file.FlatFileItemWriter. It takes two information1) the resource file where the information has to be written2) An instance of LineAggregator…… Continue reading Spring Batch Simple Example Part 2
Spring Batch Simple Example Part 1
In this post and next post, I will introduce Spring Batch to you with a simple example. Spring batch is an open source framework useful for exporting data from source to destination in batches. The framework is very useful for batch applications. Reading data In our example, we will read employee records and move them…… Continue reading Spring Batch Simple Example Part 1
Creating filters in JAX-RS
This post explains how to create filters in JAX-RS code. The filters can be placed before and after the web resource. So we can use the filters for 1) modifying the request 2) restricting certain requests from reaching the webresource 3) modifying the response In the below code I have created a custom filter, which…… Continue reading Creating filters in JAX-RS
BeanParam annotation example
This post will explain the use of BeanParam annotation in JAX-RS with an example. The purpose of BeanParam annotation is to consolidate all the user input (i.e., input through QueryParam, HeaderParam, FormParam, etc) and inject into a given class instance variables. Below is an example of webresource whose only method “retrieveRecord1” has a parameter annotated…… Continue reading BeanParam annotation example
Mapping exceptions to Response in JAX-RS
In JAX-RS, we can map exceptions to a Response. This will be useful in hiding the exceptions from the client of JAX-RS web services. Below is an example showing how to map exceptions to appropriate responses. First we need to implement ExceptionMapper interface as shown below. Here we want to map NullPointer exception to Internal…… Continue reading Mapping exceptions to Response in JAX-RS
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