Initial commit

.gitignore

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+# Project exclude paths
+/target/

pom.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<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>
+
+    <groupId>com.ocolak</groupId>
+    <artifactId>DBJUnitTestExample</artifactId>
+    <version>1.0-SNAPSHOT</version>
+
+    <properties>
+        <maven.compiler.source>16</maven.compiler.source>
+        <maven.compiler.target>16</maven.compiler.target>
+    </properties>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.apache.logging.log4j</groupId>
+            <artifactId>log4j-core</artifactId>
+            <version>[2.13.2,)</version>
+        </dependency>
+        <dependency>
+            <groupId>org.apache.logging.log4j</groupId>
+            <artifactId>log4j-api</artifactId>
+            <version>[2.13.2,)</version>
+        </dependency>
+        <!-- Provided -->
+        <dependency>
+            <groupId>org.projectlombok</groupId>
+            <artifactId>lombok</artifactId>
+            <version>1.18.20</version>
+            <scope>provided</scope>
+        </dependency>
+        <!-- JAVA EE dependencies -->
+        <dependency> <!-- Java EE -->
+            <groupId>javax</groupId>
+            <artifactId>javaee-api</artifactId>
+            <version>8.0</version>
+            <scope>provided</scope>
+        </dependency>
+        <!-- need for entityManager tests: PersistenceException: No Persistence provider for EntityManager named persistence-unit-test -->
+        <dependency>
+            <groupId>org.eclipse.persistence</groupId>
+            <artifactId>eclipselink</artifactId>
+            <version>2.7.9</version>
+            <scope>provided</scope>
+        </dependency>
+        <!-- Test -->
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-engine</artifactId>
+            <version>5.7.1</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.platform</groupId>
+            <artifactId>junit-platform-runner</artifactId>
+            <version>1.7.1</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.mockito</groupId>
+            <artifactId>mockito-junit-jupiter</artifactId>
+            <version>3.8.0</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.hamcrest</groupId>
+            <artifactId>hamcrest</artifactId>
+            <version>2.2</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>com.h2database</groupId>
+            <artifactId>h2</artifactId>
+            <version>1.4.200</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+</project>

src/main/java/com/ocolak/dao/GenericDao.java

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+package com.ocolak.dao;
+
+import java.util.List;
+
+import javax.persistence.EntityManager;
+
+public interface GenericDao<K, E> {
+
+    List<E> findAll();
+
+    E getByField(String field, String value);
+
+    E getById(K key);
+
+    EntityManager getEntityManager();
+
+}

src/main/java/com/ocolak/dao/impl/BookDaoImpl.java

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+package com.ocolak.dao.impl;
+
+import com.ocolak.entity.Book;
+
+import javax.ejb.Stateless;
+import javax.persistence.EntityManager;
+import javax.persistence.PersistenceContext;
+
+
+@Stateless
+public class BookDaoImpl extends GenericDaoImpl<Integer, Book> {
+    @PersistenceContext(unitName = "persistence-unit")
+    protected EntityManager em;
+
+    @Override
+    public EntityManager getEntityManager() {
+        return em;
+    }
+}

src/main/java/com/ocolak/dao/impl/GenericDaoImpl.java

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+package com.ocolak.dao.impl;
+
+import java.lang.reflect.ParameterizedType;
+import java.lang.reflect.Type;
+import java.util.List;
+
+
+import com.ocolak.dao.GenericDao;
+import lombok.extern.log4j.Log4j2;
+
+@Log4j2
+public abstract class GenericDaoImpl<K, E> implements GenericDao<K, E> {
+
+    private Class<E> persistentClass;
+
+    @SuppressWarnings("unchecked")
+    public GenericDaoImpl() {
+        Type genericSuperClass = getClass().getGenericSuperclass();
+
+        ParameterizedType parametrizedType = null;
+        while (parametrizedType == null) {
+            if (genericSuperClass instanceof ParameterizedType) {
+                parametrizedType = (ParameterizedType) genericSuperClass;
+            } else {
+                genericSuperClass = ((Class<?>) genericSuperClass).getGenericSuperclass();
+            }
+        }
+        this.persistentClass = (Class<E>) parametrizedType.getActualTypeArguments()[1];
+    }
+
+    @Override
+    public List<E> findAll() {
+        return getEntityManager().createNamedQuery(String.format("%s.findAll", persistentClass.getSimpleName()), persistentClass)
+                .getResultList();
+    }
+
+    @Override
+    public E getByField(final String field, final String value) {
+        log.debug(String.format("persistentClass: %s", persistentClass.getSimpleName()));
+        log.debug(String.format("field: %s", field));
+        return getEntityManager()
+                .createQuery(String.format("SELECT t FROM %s t where t.%s = :value", persistentClass.getSimpleName(), field),
+                        persistentClass)
+                .setParameter("value", value).getResultStream().findFirst().orElse(null);
+    }
+
+    @Override
+    public E getById(final K key) {
+        return getEntityManager().find(persistentClass, key);
+    }
+}