| 22. 11. 1. 映射关系 |
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File: Project.java |
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import java.util.ArrayList;
import java.util.Collection;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.OneToMany;
@Entity
public class Project {
@Id private int id;
private String name;
@OneToMany(mappedBy="project")
private Collection<ProjectAssignment> assignments;
public Project() {
assignments = new ArrayList<ProjectAssignment>();
}
public int getId() {
return id;
}
public void setId(int projectNo) {
this.id = projectNo;
}
public String getName() {
return name;
}
public void setName(String projectName) {
this.name = projectName;
}
public Collection<ProjectAssignment> getAssignments() {
return assignments;
}
public String toString() {
return " no: " + getId() +
", name: " + getName();
}
}
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File: ProjectAssignment.java |
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import java.util.Date;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.IdClass;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.Table;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;
@Entity
@Table(name="EMP_PROJECT")
@IdClass(ProjectAssignmentId.class)
public class ProjectAssignment {
@Id
@Column(name="EMP_ID", insertable=false, updatable=false)
private int studentId;
@Id
@Column(name="PROJECT_ID", insertable=false, updatable=false)
private int projectId;
@ManyToOne
@JoinColumn(name="EMP_ID")
Student student;
@ManyToOne
@JoinColumn(name="PROJECT_ID")
Project project;
public ProjectAssignment() {}
public ProjectAssignment(Student emp, Project proj) {
this.studentId = emp.getId();
this.student = emp;
this.projectId = proj.getId();
this.project = proj;
}
public int getEmpId() {
return studentId;
}
public Student getEmployee() {
return student;
}
public int getProjectId() {
return projectId;
}
public Project getProject() {
return project;
}
}
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File: ProjectAssignmentId.java |
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import java.io.Serializable;
public class ProjectAssignmentId implements Serializable {
private int studentId;
private int projectId;
public ProjectAssignmentId() {
}
public ProjectAssignmentId(int Id, int projectId) {
this.studentId = Id;
this.projectId = projectId;
}
public int getEmpId() {
return studentId;
}
public int getProjectId() {
return projectId;
}
public boolean equals(Object o) {
return ((o instanceof ProjectAssignmentId) && studentId == ((ProjectAssignmentId) o).getEmpId() && projectId == ((ProjectAssignmentId) o)
.getProjectId());
}
public int hashCode() {
return studentId + projectId;
}
}
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File: Student.java |
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import java.util.ArrayList;
import java.util.Collection;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.OneToMany;
@Entity
public class Student {
@Id private int id;
private String name;
@OneToMany(mappedBy="student")
private Collection<ProjectAssignment> assignments;
public Student() {
assignments = new ArrayList<ProjectAssignment>();
}
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 Collection<ProjectAssignment> getAssignments() {
return assignments;
}
public String toString() {
return "Student id: " + getId() + " name: " + getName();
}
}
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File: Helper.java |
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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();
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");
}
}
}
}
}
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File: Main.java |
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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();
em.getTransaction().commit();
em.close();
emf.close();
Helper.checkData();
}
}
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File: persistence.xml |
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<persistence xmlns="http://java.sun.com/xml/ns/persistence"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence" version="1.0">
<persistence-unit name="JPAService" transaction-type="RESOURCE_LOCAL">
<properties>
<property name="hibernate.dialect" value="org.hibernate.dialect.HSQLDialect"/>
<property name="hibernate.hbm2ddl.auto" value="update"/>
<property name="hibernate.connection.driver_class" value="org.hsqldb.jdbcDriver"/>
<property name="hibernate.connection.username" value="sa"/>
<property name="hibernate.connection.password" value=""/>
<property name="hibernate.connection.url" value="jdbc:hsqldb:data/tutorial"/>
</properties>
</persistence-unit>
</persistence>
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 Download: JPA-MappingRelationshipState.zip( 5,291 k) |