Hibernate 5 – merge() Example
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- 2. Hibernate 5 – merge() Example How to use Session.merge()In hibernate; both merge() and update() methods updates an entity and can also affect the state of an object i.e. from detached to persistent. In this article, we will explore the use of merge() method. method to merge an entity in Hibernate Application. Session.merge(Object object) This method copies the state of the given object onto the persistent object with the same identifier. If there is no persistent instance currently associated with the session, it will be loaded. Return the persistent instance. If the given instance is unsaved, save a copy of and return it as a newly persistent instance. The given instance does not become associated with the session. This operation cascades to associated instances if the association is mapped with cascade=”merge”.
- 3. Hibernate 5 – merge() Example Add jar Dependencies to pom.xml < project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> < modelVersion>4.0.0< /modelVersion> < parent> < groupId>net.ducatindia.hibernate< /groupId> < artifactId>hibernate-tutorial< /artifactId> < version>0.0.1-SNAPSHOT< /version> < /parent> < artifactId>hibernate-merge-entity-example< /artifactId> < properties> < project.build.sourceEncoding>UTF-8< /project.build.sourceEncoding> < /properties> < dependencies> < !-- https://mvnrepository.com/artifact/mysql/mysql-connector-java --> < dependency> < groupId>mysql< /groupId> < artifactId>mysql-connector-java< /artifactId>
- 4. < version>8.0.13< /version> < /dependency> < !-- https://mvnrepository.com/artifact/org.hibernate/hibernate-core --> < dependency> < groupId>org.hibernate< /groupId> < artifactId>hibernate-core< /artifactId> < version>5.3.7.Final< /version> < /dependency> < /dependencies> < build> < sourceDirectory>src/main/java< /sourceDirectory> < plugins> < plugin> < artifactId>maven-compiler-plugin< /artifactId> < version>3.5.1< /version> < configuration> < source>1.8< /source> < target>1.8< /target> < /configuration> < /plugin> < /plugins> < /build> < /project>
- 5. Creating the JPA Entity Class(Persistent class) A simple Persistent class should follow some rules: • A no-arg constructor: It is recommended that you have a default constructor at least package visibility so that hibernate can create the instance of the Persistent class by newInstance() method. • Provide an identifier property: It is better to assign an attribute as id. This attribute behaves as a primary key in a database. • Declare getter and setter methods: The Hibernate recognizes the method by getter and setter method names by default. • Prefer non-final class: Hibernate uses the concept of proxies, that depends on the persistent class. The application programmer will not be able to use proxies for lazy association fetching. Read More: https://tutorials.ducatindia.com/java/hibernate-5-merge-example/