This post explains how to handle errors generated while deserializing the json file. This can be achieved by implementing an interface “DeserializationProblemHandler” provided by jackson framework as shown below UnMarshallingErrorHandler package package1; import java.io.IOException; import com.fasterxml.jackson.core.JsonParser; import com.fasterxml.jackson.core.JsonProcessingException; import com.fasterxml.jackson.databind.DeserializationContext; import com.fasterxml.jackson.databind.JsonDeserializer; import com.fasterxml.jackson.databind.deser.DeserializationProblemHandler; public class UnMarshallingErrorHandler extends DeserializationProblemHandler { @Override public boolean handleUnknownProperty(DeserializationContext ctxt,…… Continue reading Handling json deserialization error
Executing compiled script
In the previous posts under “Java Scripting”, we used ScriptEngine eval method to execute scripts stored in a string variable or file. The ScriptEngine’s eval methods takes the script compiles to intermediate code and execute it immediately. If we have a script which has to be executed repeatedly, then instead of compiling and executing it…… Continue reading Executing compiled script
Combining Predicates
This post explains how we can combine two or more predicates using logical operations as mentioned below 1) and 2) or 3) negate Below is an example Person package Function; public class Person { private String ssn; private String fname; private String lname; private String description; private int age; public String getSsn() { return ssn;…… Continue reading Combining Predicates
Getting JsonGenerator settings
This post explains how to get JsonGenerator settings. JsonGenerator class obtained from JsonFactory is responsible for writing json data as a stream instead of constructing an entire object model in memory and then writing to destination. The list of settings that can be turned on or off are present in an enumeration JsonGenerator.Feature. The below…… Continue reading Getting JsonGenerator settings
Getting JsonFactory settings
This post explains how to get JsonFactory settings. The JsonFactory class is thread safe and responsible for creating instances of writer and reader. Creating an instance of JsonFactory is an light weight operation. The list of settings that can be turned on or off are present in an enumeration JsonFactory.Feature. The below code shows how…… Continue reading Getting JsonFactory settings
Executing sql statements as a batch through hibernate
They are two ways to execute sql statements as batch in hibernate, which are 1) Work 2) ReturningWork This approach is useful when we want to perform batch operations directly on the database instead of indirectly through hibernate. First we will implement the Work interface as shown below JdbcWork class JdbcWork implements Work { private…… Continue reading Executing sql statements as a batch through hibernate
Mocking Static class methods
In Mockito we cannot mock static class methods, so we can use PowerMock which extends the Mockito features and provides its own features. One of which is mocking static class methods. Below code will give an example how to mock static class methods Calculator package package1; public class Calculator { public static int add(int value1,…… Continue reading Mocking Static class methods
Java Predicate
Java provides a new interface named Predicate which is a functional interface. A functional interface is an interface which will have exactly one abstract method in addition to one or more default methods. In the case of Predicate interface, the abstract method is test method whose signature is as shown below boolean test(T t) In…… Continue reading Java Predicate
Getting access to all printers configured in machine
This post explains how to programmatically get access to all printers configured in a machine. Java provides lookup facitlity through PrintServiceLookup class. This class has static methods through which we can get a reference to all the printers. We use the lookupPrintServices method in the PrintServiceLookup class. The api definition is as shown below public…… Continue reading Getting access to all printers configured in machine
Executing scripts written in a file using java
This post explain how to execute javascript code stored in a file. We create an instance of FileReader representing the physical file and pass it to eval method of an instance of ScriptEngine. Please refer to previous posts to know more about ScriptEngine and ScriptEngineManager The javascript code in the file that has to be…… Continue reading Executing scripts written in a file using java
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