initial

.gitignore

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+*.iml
+target
+derby.log

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>jpa-builder-pattern</groupId>
+    <artifactId>jpa-builder-pattern</artifactId>
+    <version>1.0-SNAPSHOT</version>
+
+    <properties>
+        <maven.compiler.source>1.8</maven.compiler.source>
+        <maven.compiler.target>1.8</maven.compiler.target>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
+    </properties>
+
+    <dependencies>
+        <dependency>
+            <groupId>com.google.inject</groupId>
+            <artifactId>guice</artifactId>
+            <version>4.1.0</version>
+        </dependency>
+        <dependency>
+            <groupId>com.google.inject.extensions</groupId>
+            <artifactId>guice-persist</artifactId>
+            <version>4.1.0</version>
+        </dependency>
+        <dependency>
+            <groupId>org.eclipse.persistence</groupId>
+            <artifactId>eclipselink</artifactId>
+            <version>2.5.1</version>
+        </dependency>
+        <dependency>
+            <groupId>org.apache.derby</groupId>
+            <artifactId>derby</artifactId>
+            <version>10.12.1.1</version>
+            <scope>runtime</scope>
+        </dependency>
+        <dependency>
+            <groupId>junit</groupId>
+            <artifactId>junit</artifactId>
+            <version>4.12</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.hamcrest</groupId>
+            <artifactId>hamcrest-all</artifactId>
+            <version>1.3</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+</project>

src/main/java/entity/AbstractEntity.java

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+package entity;
+
+import javax.persistence.GeneratedValue;
+import javax.persistence.Id;
+import javax.persistence.MappedSuperclass;
+
+@MappedSuperclass
+class AbstractEntity {
+    @Id
+    @GeneratedValue
+    private Long id;
+
+    public Long getId() {
+        return id;
+    }
+
+    public void setId(final Long id) {
+        this.id = id;
+    }
+}

src/main/java/entity/Dept.java

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+package entity;
+
+import javax.persistence.Column;
+import javax.persistence.Entity;
+import javax.persistence.OneToMany;
+import java.util.Collection;
+
+@Entity
+public class Dept extends AbstractEntity {
+
+    @Column(nullable = false)
+    private String name;
+    @OneToMany(mappedBy = "dept")
+    private Collection<Employee> employees;
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(final String name) {
+        this.name = name;
+    }
+
+    public Collection<Employee> getEmployees() {
+        return employees;
+    }
+
+    public void setEmployees(final Collection<Employee> employees) {
+        this.employees = employees;
+    }
+}

src/main/java/entity/Employee.java

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+package entity;
+
+import javax.persistence.Column;
+import javax.persistence.Entity;
+import javax.persistence.JoinColumn;
+import javax.persistence.ManyToMany;
+import javax.persistence.ManyToOne;
+import javax.persistence.OneToMany;
+import java.util.Collection;
+
+@Entity
+public class Employee extends AbstractEntity {
+
+    @Column(nullable = false)
+    private String name;
+    @Column(nullable = false, name = "temporary_emp")
+    private Boolean temporary;
+    @JoinColumn(nullable = false)
+    @ManyToOne
+    private Dept dept;
+    @ManyToMany
+    private Collection<Project> projects;
+    @OneToMany(mappedBy = "employee")
+    private Collection<Phone> phones;
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(final String name) {
+        this.name = name;
+    }
+
+    public Boolean getTemporary() {
+        return temporary;
+    }
+
+    public void setTemporary(final Boolean temporary) {
+        this.temporary = temporary;
+    }
+
+    public Dept getDept() {
+        return dept;
+    }
+
+    public void setDept(final Dept dept) {
+        this.dept = dept;
+    }
+
+    public Collection<Project> getProjects() {
+        return projects;
+    }
+
+    public void setProjects(final Collection<Project> projects) {
+        this.projects = projects;
+    }
+
+    public Collection<Phone> getPhones() {
+        return phones;
+    }
+
+    public void setPhones(final Collection<Phone> phones) {
+        this.phones = phones;
+    }
+}

src/main/java/entity/Phone.java

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+package entity;
+
+import javax.persistence.Column;
+import javax.persistence.Entity;
+import javax.persistence.JoinColumn;
+import javax.persistence.ManyToOne;
+
+@Entity
+public class Phone extends AbstractEntity {
+
+    @Column(nullable = false, unique = true)
+    private String number;
+    @ManyToOne
+    @JoinColumn(nullable = false)
+    private Employee employee;
+
+    public String getNumber() {
+        return number;
+    }
+
+    public void setNumber(final String number) {
+        this.number = number;
+    }
+
+    public Employee getEmployee() {
+        return employee;
+    }
+
+    public void setEmployee(final Employee employee) {
+        this.employee = employee;
+    }
+}

src/main/java/entity/Project.java

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+package entity;
+
+import javax.persistence.Column;
+import javax.persistence.Entity;
+import javax.persistence.ManyToMany;
+import java.util.Collection;
+
+@Entity
+public class Project extends AbstractEntity {
+
+    @Column(nullable = false)
+    private String name;
+    @ManyToMany(mappedBy = "projects")
+    private Collection<Employee> employees;
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(final String name) {
+        this.name = name;
+    }
+
+    public Collection<Employee> getEmployees() {
+        return employees;
+    }
+
+    public void setEmployees(final Collection<Employee> employees) {
+        this.employees = employees;
+    }
+}

src/main/java/service/EmployeeService.java

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+package service;
+
+import entity.Dept;
+import entity.Employee;
+import entity.Phone;
+import entity.Project;
+
+import javax.persistence.EntityManager;
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.Set;
+
+public class EmployeeService {
+
+    private final EntityManager em;
+
+    EmployeeService(final EntityManager em) {
+        this.em = em;
+    }
+
+    public long create(long deptId,
+                       String name,
+                       boolean temporary,
+                       Set<Long> projectIds,
+                       Set<String> phoneNumbers) {
+
+        // instantiating and setting attributes of employee
+        final Employee employee = new Employee();
+        employee.setName(name);
+        employee.setTemporary(temporary);
+
+        // making a relation between employee and dept
+        final Dept dept = em.find(Dept.class, deptId);
+        employee.setDept(dept);
+        dept.getEmployees().add(employee);
+
+        // making relations between employee and projects
+        employee.setProjects(new HashSet<>());
+        for (final Long projectId : projectIds) {
+            final Project project = em.find(Project.class, projectId);
+            project.getEmployees().add(employee);
+            employee.getProjects().add(project);
+        }
+
+        // creating phones
+        employee.setPhones(new HashSet<>());
+        for (final String phoneNumber : phoneNumbers) {
+            final Phone phone = new Phone();
+            phone.setNumber(phoneNumber);
+            phone.setEmployee(employee);
+            employee.getPhones().add(phone);
+            em.persist(phone);
+        }
+
+        em.persist(employee);
+        em.flush(); // making sure a generated id is present
+
+        return employee.getId();
+    }
+
+    public Builder builder(long deptId, String name) {
+        return new Builder(deptId, name);
+    }
+
+    public final class Builder { // not static
+        private final long deptId;
+        private final String name;
+        private boolean temporary;
+        private Set<Long> projectIds = new HashSet<>();
+        private Set<String> phoneNumbers = new HashSet<>();
+
+        public Builder(final long deptId, final String name) {
+            this.deptId = deptId;
+            this.name = name;
+        }
+
+        public Builder temporary() {
+            temporary = true;
+            return this;
+        }
+
+        public Builder projectIds(long... ids) {
+            for (final long id : ids) {
+                projectIds.add(id);
+            }
+            return this;
+        }
+
+        public Builder phoneNumbers(String... numbers) {
+            phoneNumbers.addAll(Arrays.asList(numbers));
+            return this;
+        }
+
+        public long build() {
+            return EmployeeService.this.create(deptId, name, temporary, projectIds, phoneNumbers);
+        }
+    }
+}

src/main/resources/META-INF/persistence.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<persistence version="2.1" xmlns="http://xmlns.jcp.org/xml/ns/persistence"
+             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+             xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd">
+    <persistence-unit name="myPU" transaction-type="RESOURCE_LOCAL">
+        <provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
+        <class>entity.Dept</class>
+        <class>entity.Employee</class>
+        <class>entity.Phone</class>
+        <class>entity.Project</class>
+        <shared-cache-mode>NONE</shared-cache-mode>
+        <properties>
+            <property name="javax.persistence.jdbc.driver" value="org.apache.derby.jdbc.EmbeddedDriver"/>
+            <property name="javax.persistence.jdbc.url" value="jdbc:derby:memory:myDB;create=true"/>
+            <property name="javax.persistence.jdbc.user" value="app"/>
+            <property name="javax.persistence.jdbc.password" value="app"/>
+
+            <property name="javax.persistence.schema-generation.database.action" value="drop-and-create"/>
+
+            <property name="eclipselink.logging.level" value="FINE"/>
+            <property name="eclipselink.logging.parameters" value="true"/>
+
+            <property name="hibernate.show_sql" value="true"/>
+        </properties>
+    </persistence-unit>
+</persistence>