StackOverflow2013

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PO
primarykey
Id
5064085
data
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0
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0
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2011-02-21T09:11:13.033
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2011-02-21T09:11:13.033
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text
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Example of your Query import java.util.HashMap; import java.util.Map; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.GenerationType; import javax.persistence.Id; import javax.persistence.MapKey; import javax.persistence.OneToMany; @Entity public class Department { @Id @GeneratedValue(strategy=GenerationType.IDENTITY) private int id; private String name; @OneToMany(mappedBy="department") @MapKey(name="name") private Map students; <pre><code>public Department() { students = new HashMap<String, Student>(); } public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String deptName) { this.name = deptName; } public void addStudent(Student student) { if (!getStudents().containsKey(student.getName())) { getStudents().put(student.getName(), student); if (student.getDepartment() != null) { student.getDepartment().getStudents().remove(student.getName()); } student.setDepartment(this); } } public Map<String,Student> getStudents() { return students; } public String toString() { return "Department id: " + getId() + ", name: " + getName(); } </code></pre> } File: Student.java import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.GenerationType; import javax.persistence.Id; import javax.persistence.ManyToOne; @Entity public class Student { @Id @GeneratedValue(strategy=GenerationType.IDENTITY) private int id; private String name; <pre><code>@ManyToOne private Department department; public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public Department getDepartment() { return department; } public void setDepartment(Department department) { this.department = department; } public String toString() { return "Student id: " + getId() + " name: " + getName() + " with " + getDepartment(); } </code></pre> } File: Helper.java import java.sql.Connection; import java.sql.DriverManager; import java.sql.ResultSet; import java.sql.ResultSetMetaData; import java.sql.Statement; public class Helper { public static void checkData() throws Exception { Class.forName("org.hsqldb.jdbcDriver"); Connection conn = DriverManager.getConnection("jdbc:hsqldb:data/tutorial", "sa", ""); Statement st = conn.createStatement(); <pre><code>ResultSet mrs = conn.getMetaData().getTables(null, null, null, new String[] { "TABLE" }); while (mrs.next()) { String tableName = mrs.getString(3); System.out.println("\n\n\n\nTable Name: "+ tableName); ResultSet rs = st.executeQuery("select * from " + tableName); ResultSetMetaData metadata = rs.getMetaData(); while (rs.next()) { System.out.println(" Row:"); for (int i = 0; i < metadata.getColumnCount(); i++) { System.out.println(" Column Name: "+ metadata.getColumnLabel(i + 1)+ ", "); System.out.println(" Column Type: "+ metadata.getColumnTypeName(i + 1)+ ": "); Object value = rs.getObject(i + 1); System.out.println(" Column Value: "+value+"\n"); } } } </code></pre> } } File: Main.java import java.util.List; import javax.persistence.EntityManager; import javax.persistence.EntityManagerFactory; import javax.persistence.Persistence; import javax.persistence.Query; public class Main { static EntityManagerFactory emf = Persistence.createEntityManagerFactory("JPAService"); static EntityManager em = emf.createEntityManager(); public static void main(String[] a) throws Exception { em.getTransaction().begin(); <pre><code>Student student = new Student(); student.setName("Joe"); em.persist(student); Department dept = new Department(); dept.addStudent(student); em.persist(dept); em.flush(); Query query = em.createQuery("SELECT e FROM Student e"); List<Student> list = (List<Student>) query.getResultList(); System.out.println(list); query = em.createQuery("SELECT d FROM Department d"); List<Department> dList = (List<Department>) query.getResultList(); System.out.println(dList); em.getTransaction().commit(); em.close(); emf.close(); Helper.checkData(); </code></pre> } } File: persistence.xml http://java.sun.com/xml/ns/persistence/persistence" version="1.0"> 
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1. This table or related slice is empty.
PostParentId
1. POEclipselink @mapkey and @JoinFetch(JoinFetchType.OUTER) cannot co-exist?
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1. PTAnswer
UserLastEditorUserId
1. This table or related slice is empty.
UserOwnerUserId
1. USVolatilitySmile
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1. This table or related slice is empty.
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1. This table or related slice is empty.
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1. This table or related slice is empty.
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Querying!

Guidance

A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.