The result type of a query is determined by the expressions listed in the SELECT clause of the query.
The query result from a Query is a List of Object. And the Object in the list can be an Object[].
The following code loop through the list of object and output one by one. If the object is an Object[] it also loops that array.
private void printQueryResult(String queryString, List result) { System.out.println("EJB QL: " + queryString+"\n"); System.out.println("Result:\n"); if (result.isEmpty()) { System.out.println("No results Found\n"); } else { for (Object o : result) { System.out.println(resultAsString(o)); } } } private String resultAsString(Object o) { if (o instanceof Object[]) { return Arrays.asList((Object[])o).toString(); } else { return String.valueOf(o); } }
The following code is from Project.java.
package com.java2s.common; import java.util.ArrayList; import java.util.Collection; import javax.persistence.Entity; import javax.persistence.Id; import javax.persistence.ManyToMany; @Entity public class Project { @Id protected int id; protected String name; @ManyToMany(mappedBy="projects") private Collection<Employee> employees; public Project() { employees = new ArrayList<Employee>(); } public void setId(int id) { this.id = id; } public void setName(String name) { this.name = name; } public void setEmployees(Collection<Employee> employees) { this.employees = employees; } public int getId() { return id; } public String getName() { return name; } public Collection<Employee> getEmployees() { return employees; } public String toString() { return "Project id: " + getId() + ", name: " + getName(); } }
The following code is from Employee.java.
package com.java2s.common; import java.util.ArrayList; import java.util.Collection; import java.util.Date; import javax.persistence.Entity; import javax.persistence.Id; import javax.persistence.ManyToMany; import javax.persistence.ManyToOne; import javax.persistence.NamedQueries; import javax.persistence.NamedQuery; import javax.persistence.OneToMany; import javax.persistence.Temporal; import javax.persistence.TemporalType; @Entity public class Employee { @Id private int id; private String name; private long salary; @Temporal(TemporalType.DATE) private Date startDate; @ManyToOne private Employee manager; @OneToMany(mappedBy="manager") private Collection<Employee> directs; @ManyToOne private Department department; @ManyToMany private Collection<Project> projects; public Employee() { projects = new ArrayList<Project>(); directs = new ArrayList<Employee>(); } public void setId(int id) { this.id = id; } public void setName(String name) { this.name = name; } public void setSalary(long salary) { this.salary = salary; } public void setStartDate(Date startDate) { this.startDate = startDate; } public void setManager(Employee manager) { this.manager = manager; } public void setDirects(Collection<Employee> directs) { this.directs = directs; } public void setDepartment(Department department) { this.department = department; } public void setProjects(Collection<Project> projects) { this.projects = projects; } public int getId() { return id; } public String getName() { return name; } public long getSalary() { return salary; } public Date getStartDate() { return startDate; } public Department getDepartment() { return department; } public Collection<Employee> getDirects() { return directs; } public Employee getManager() { return manager; } public Collection<Project> getProjects() { return projects; } public String toString() { return "Employee " + getId() + ": name: " + getName() + ", salary: " + getSalary() + ", dept: " + ((getDepartment() == null) ? null : getDepartment().getName()); } }
The following code is from PersonDaoImpl.java.
package com.java2s.common; import java.io.PrintWriter; import java.util.Arrays; import java.util.Date; import java.util.List; import javax.persistence.EntityManager; import javax.persistence.PersistenceContext; import javax.persistence.Query; import org.springframework.transaction.annotation.Transactional; @Transactional public class PersonDaoImpl { public void test() { Employee emp = new Employee(); emp.setName("Tom"); emp.setSalary(123); emp.setStartDate(new Date()); emp.setId(1); Project pro = new Project(); pro.setName("Design"); pro.getEmployees().add(emp); Department dept = new Department(); dept.setName("Dept"); dept.getEmployees().add(emp); emp.setDepartment(dept); emp.getProjects().add(pro); em.persist(dept); em.persist(pro); em.persist(emp); executeAndPrintQuery("SELECT e.department FROM Employee e"); } private void executeAndPrintQuery(String queryString) { try { Query query = em.createQuery(queryString); printQueryResult(queryString, query.getResultList()); } finally { em.close(); } } private void printQueryResult(String queryString, List result) { System.out.println("EJB QL: " + queryString+"\n"); System.out.println("Result:\n"); if (result.isEmpty()) { System.out.println("No results Found\n"); } else { for (Object o : result) { System.out.println(resultAsString(o)); } } } private String resultAsString(Object o) { if (o instanceof Object[]) { return Arrays.asList((Object[])o).toString(); } else { return String.valueOf(o); } } @PersistenceContext private EntityManager em; }
The following code is from Department.java.
package com.java2s.common; import java.util.ArrayList; import java.util.Collection; import javax.persistence.Entity; import javax.persistence.Id; import javax.persistence.OneToMany; @Entity public class Department { @Id private int id; private String name; @OneToMany(mappedBy="department") private Collection<Employee> employees; public Department() { employees = new ArrayList<Employee>(); } public void setId(int id) { this.id = id; } public void setName(String name) { this.name = name; } public void setEmployees(Collection<Employee> employees) { this.employees = employees; } public int getId() { return id; } public String getName() { return name; } public Collection<Employee> getEmployees() { return employees; } public String toString() { return "Department no: " + getId() + ", name: " + getName(); } }
The code above generates the following result.
The following is the database dump.
Table Name: DEPARTMENT Row: Column Name: ID, Column Type: INTEGER: Column Value: 0 Column Name: NAME, Column Type: VARCHAR: Column Value: Dept Table Name: EMPLOYEE Row: Column Name: ID, Column Type: INTEGER: Column Value: 1 Column Name: NAME, Column Type: VARCHAR: Column Value: Tom Column Name: SALARY, Column Type: BIGINT: Column Value: 123 Column Name: STARTDATE, Column Type: DATE: Column Value: 2014-12-29 Column Name: DEPARTMENT_ID, Column Type: INTEGER: Column Value: 0 Column Name: MANAGER_ID, Column Type: INTEGER: Column Value: null Table Name: EMPLOYEE_PROJECT Row: Column Name: EMPLOYEES_ID, Column Type: INTEGER: Column Value: 1 Column Name: PROJECTS_ID, Column Type: INTEGER: Column Value: 0 Table Name: PROJECT Row: Column Name: ID, Column Type: INTEGER: Column Value: 0 Column Name: NAME, Column Type: VARCHAR: Column Value: Design