```java import org.w3c.dom.Document; import javax.xml.parsers.DocumentBuilder; import javax.xml.parsers.DocumentBuilderFactory; public class XMLParser { public static void main(String[] args) { try { DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance(); DocumentBuilder builder = factory.newDocumentBuilder(); Document doc = builder.parse("example.xml"); } catch (Exception e) { e.printStackTrace(); } } } ``` ```java import org.xml.sax.Attributes; import org.xml.sax.SAXException; import org.xml.sax.helpers.DefaultHandler; import javax.xml.parsers.SAXParser; import javax.xml.parsers.SAXParserFactory; public class XMLParser { public static void main(String[] args) { try { SAXParserFactory factory = SAXParserFactory.newInstance(); SAXParser parser = factory.newSAXParser(); parser.parse("example.xml", new XMLHandler()); } catch (Exception e) { e.printStackTrace(); } } static class XMLHandler extends DefaultHandler { @Override public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException { } @Override public void endElement(String uri, String localName, String qName) throws SAXException { } @Override public void characters(char[] ch, int start, int length) throws SAXException { } } } ``` ```java import org.w3c.dom.Document; import org.w3c.dom.Element; import javax.xml.parsers.DocumentBuilder; import javax.xml.parsers.DocumentBuilderFactory; import javax.xml.transform.Transformer; import javax.xml.transform.TransformerFactory; import javax.xml.transform.dom.DOMSource; import javax.xml.transform.stream.StreamResult; public class XMLGenerator { public static void main(String[] args) { try { DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance(); DocumentBuilder builder = factory.newDocumentBuilder(); Document doc = builder.newDocument(); Element rootElement = doc.createElement("employees"); doc.appendChild(rootElement); Element employeeElement = doc.createElement("employee"); rootElement.appendChild(employeeElement); employeeElement.setAttribute("id", "1"); TransformerFactory transformerFactory = TransformerFactory.newInstance(); Transformer transformer = transformerFactory.newTransformer(); DOMSource source = new DOMSource(doc); StreamResult result = new StreamResult("example.xml"); transformer.transform(source, result); } catch (Exception e) { e.printStackTrace(); } } } ``` ```java import jakarta.xml.bind.JAXBContext; import jakarta.xml.bind.JAXBException; import jakarta.xml.bind.Marshaller; import java.io.File; public class XMLGenerator { public static void main(String[] args) { try { JAXBContext context = JAXBContext.newInstance(Employee.class); Marshaller marshaller = context.createMarshaller(); marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true); Employee employee = new Employee(); employee.setId(1); employee.setName("John Doe"); marshaller.marshal(employee, new File("example.xml")); } catch (JAXBException e) { e.printStackTrace(); } } static class Employee { private int id; private String name; } } ```

```java public abstract class BaseEntity { @Id @GeneratedValue(strategy = GenerationType.AUTO) private Long id; // Getters and setters } @Entity @Table(name = "employees") public class Employee extends BaseEntity { private String firstName; private String lastName; // Getters and setters } @Entity @Table(name = "managers") public class Manager extends Employee { private String department; // Getters and setters } ``` ```java @Entity @Table(name = "departments") public class Department { @Id @GeneratedValue(strategy = GenerationType.AUTO) private Long id; @OneToMany(mappedBy = "department") private List<Employee> employees; // Getters and setters } @Entity @Table(name = "employees") public class Employee { @Id @GeneratedValue(strategy = GenerationType.AUTO) private Long id; @ManyToOne @JoinColumn(name = "department_id") private Department department; // Getters and setters } ``` ```java @Entity @Table(name = "departments") public class Department { @Id @GeneratedValue(strategy = GenerationType.AUTO) private Long id; @OneToMany(mappedBy = "department", fetch = FetchType.LAZY) private List<Employee> employees; // Getters and setters } ``` ```java @Entity @Table(name = "employees") @Cacheable public class Employee { @Id @GeneratedValue(strategy = GenerationType.AUTO) private Long id; // Other fields // Getters and setters } ``` ```java public List<Employee> getEmployeesByDepartment(String departmentName) { Query query = entityManager.createQuery("SELECT e FROM Employee e JOIN e.department d WHERE d.name = :departmentName"); query.setParameter("departmentName", departmentName); return query.getResultList(); } ```

```java import org.datanucleus.api.jdo.JDOPersistenceManagerFactory; public class PersistenceExample { private static final String DB_URL = "jdbc:mysql://localhost:3306/mydatabase"; private static final String DB_USERNAME = "myuser"; private static final String DB_PASSWORD = "mypassword"; public static void main(String[] args) { JDOPersistenceManagerFactory pmf = new JDOPersistenceManagerFactory(); pmf.setProperty("javax.jdo.option.ConnectionURL", DB_URL); pmf.setProperty("javax.jdo.option.ConnectionUserName", DB_USERNAME); pmf.setProperty("javax.jdo.option.ConnectionPassword", DB_PASSWORD); PersistenceManager pm = pmf.getPersistenceManager(); try { Person person = new Person("John Doe", 30); pm.currentTransaction().begin(); pm.makePersistent(person); pm.currentTransaction().commit(); Query query = pm.newQuery(Person.class); List<Person> persons = (List<Person>) query.execute(); for (Person p : persons) { System.out.println(p.getName() + " - " + p.getAge()); } } finally { pm.close(); } } } ```

```xml <dependency> <groupId>org.jpox</groupId> <artifactId>jpox-core</artifactId> <version>2.2.0-final</version> </dependency> ``` ```xml <?xml version="1.0" encoding="UTF-8"?> <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_2_0.xsd" version="2.0"> <persistence-unit name="jdo"> <provider>org.jpox.PersistenceProviderImpl</provider> <properties> <property name="javax.jdo.option.ConnectionURL" value="jdbc:mysql://localhost:3306/mydb"/> <property name="javax.jdo.option.ConnectionDriverName" value="com.mysql.jdbc.Driver"/> <property name="javax.jdo.option.ConnectionUserName" value="root"/> <property name="javax.jdo.option.ConnectionPassword" value="password"/> </properties> </persistence-unit> </persistence> ``` ```xml <plugin> <groupId>jpox</groupId> <artifactId>maven-jpox-plugin</artifactId> <version>2.2.0</version> <configuration> <propsFile>maven-jdo-plugin.props</propsFile> <useDefaultFile>false</useDefaultFile> </configuration> <executions> <execution> <goals> <goal>enhancer</goal> </goals> </execution> </executions> <dependencies> <dependency> <groupId>org.jpox</groupId> <artifactId>jpox</artifactId> <version>2.2.0-final</version> </dependency> </dependencies> </plugin> ``` ``` mvn clean install jpox:enhancer ```

```java import org.datanucleus.api.jdo.JDOPersistenceManagerFactory; public class JPOXDemo { public static void main(String[] args) { JDOPersistenceManagerFactory pmf = new JDOPersistenceManagerFactory(); pmf.setProperty("javax.jdo.option.ConnectionURL", "jdbc:mysql://localhost:3306/mydatabase"); pmf.setProperty("javax.jdo.option.ConnectionDriverName", "com.mysql.jdbc.Driver"); pmf.setProperty("javax.jdo.option.ConnectionUserName", "root"); pmf.setProperty("javax.jdo.option.ConnectionPassword", "password"); PersistenceManager pm = pmf.getPersistenceManager(); try { pm.currentTransaction().begin(); MyObject obj = new MyObject(); obj.setName("John"); obj.setAge(25); pm.makePersistent(obj); pm.currentTransaction().commit(); Query query = pm.newQuery(MyObject.class); List<MyObject> results = (List<MyObject>) query.execute(); for (MyObject result : results) { System.out.println(result.getName() + " - " + result.getAge()); } } finally { pm.close(); } } } import javax.jdo.annotations.*; @PersistenceCapable public class MyObject { @PrimaryKey private String name; @Persistent private int age; } ```

```java public class BankAccount { private int accountNumber; private double balance; // Getter and Setter methods public void deposit(double amount) { balance += amount; } public void withdraw(double amount) { if (balance >= amount) { balance -= amount; } } public void transfer(BankAccount destination, double amount) { try { this.withdraw(amount); destination.deposit(amount); System.out.println("Transfer successful!"); } catch (Exception e) { System.out.println("Transfer failed!"); throw e; } } } ``` ```xml <transaction name="tx" nontransactional-read="false" nontransactional-write="false" isolation="read-committed"/> ``` ```java import javax.jdo.JDOHelper; import javax.jdo.PersistenceManager; import javax.jdo.Transaction; public class Main { public static void main(String[] args) { PersistenceManager pm = JDOHelper.getPersistenceManagerFactory("jdoconfig.xml").getPersistenceManager(); try { Transaction tx = pm.currentTransaction(); tx.begin(); BankAccount source = pm.getObjectById(BankAccount.class, 1); BankAccount destination = pm.getObjectById(BankAccount.class, 2); source.transfer(destination, 100.0); tx.commit(); System.out.println("Transaction committed successfully!"); } catch (Exception e) { System.out.println("Transaction failed!"); } finally { if (tx.isActive()) { tx.rollback(); } pm.close(); } } } ```

```java import javax.jdo.PersistenceManager; import javax.jdo.PersistenceManagerFactory; import javax.jdo.Query; public class JPOXCoreExample { private static PersistenceManagerFactory pmf; public static void main(String[] args) { pmf = JDOHelper.getPersistenceManagerFactory("jdoconfig.xml"); try { PersistenceManager pm = pmf.getPersistenceManager(); Transaction tx = pm.currentTransaction(); tx.begin(); Query query = pm.newQuery(Person.class); List<Person> persons = (List<Person>) query.execute(); for (Person person : persons) { // do something } tx.commit(); } finally { if (tx.isActive()) { tx.rollback(); } pm.close(); } } } ```

```java @Entity @Table(name = "employees") public class Employee { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private Long id; @Column(name = "name") private String name; // getters and setters } public List<Employee> getAllEmployees() { EntityManagerFactory emf = Persistence.createEntityManagerFactory("my-persistence-unit"); EntityManager em = emf.createEntityManager(); TypedQuery<Employee> query = em.createQuery("SELECT e FROM Employee e", Employee.class); return query.getResultList(); } ``` ```xml <?xml version="1.0" encoding="UTF-8"?> <persistence 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_2.xsd" version="2.2"> <persistence-unit name="my-persistence-unit" transaction-type="RESOURCE_LOCAL"> <provider>org.jpox.PersistenceProviderImpl</provider> <properties> <property name="javax.persistence.jdbc.url" value="jdbc:mysql://localhost:3306/mydb"/> <property name="javax.persistence.jdbc.user" value="root"/> <property name="javax.persistence.jdbc.password" value="password"/> </properties> </persistence-unit> </persistence> ``` ```java public class EmployeeMapper { public List<Employee> getAllEmployees() { SqlSessionFactory sessionFactory = getSqlSessionFactory(); try (SqlSession session = sessionFactory.openSession()) { EmployeeMapper mapper = session.getMapper(EmployeeMapper.class); return mapper.getAllEmployees(); } } @Select("SELECT * FROM employees") List<Employee> getAllEmployees(); private SqlSessionFactory getSqlSessionFactory() { String resource = "mybatis-config.xml"; try (InputStream inputStream = Resources.getResourceAsStream(resource)) { return new SqlSessionFactoryBuilder().build(inputStream); } catch (IOException e) { throw new RuntimeException("Error initializing MyBatis.", e); } } } ``` ```xml <configuration> <environments default="development"> <environment id="development"> <transactionManager type="JDBC"/> <dataSource type="POOLED"> <property name="driver" value="com.mysql.jdbc.Driver"/> <property name="url" value="jdbc:mysql://localhost:3306/mydb"/> <property name="username" value="root"/> <property name="password" value="password"/> </dataSource> </environment> </environments> <mappers> <mapper class="com.example.EmployeeMapper"/> </mappers> </configuration> ```

``` <dependencies> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-context</artifactId> <version>5.3.8</version> </dependency> <dependency> <groupId>org.datanucleus</groupId> <artifactId>datanucleus-core</artifactId> <version>5.2.5</version> </dependency> <dependency> <groupId>org.datanucleus</groupId> <artifactId>datanucleus-api-jpa</artifactId> <version>5.2.4</version> </dependency> </dependencies> ``` ``` <?xml version="1.0" encoding="UTF-8"?> <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_2_0.xsd" version="2.0"> <persistence-unit name="myPersistenceUnit" transaction-type="RESOURCE_LOCAL"> <provider>org.datanucleus.api.jpa.PersistenceProviderImpl</provider> <class>com.example.entity.User</class> <properties> <property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver" /> <property name="javax.persistence.jdbc.url" value="jdbc:mysql://localhost:3306/mydatabase" /> <property name="javax.persistence.jdbc.user" value="username" /> <property name="javax.persistence.jdbc.password" value="password" /> <property name="datanucleus.autoCreateSchema" value="true" /> <property name="datanucleus.schema.autoCreateAll" value="true" /> </properties> </persistence-unit> </persistence> ``` ```java @Entity @Table(name = "users") public class User { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private Long id; @Column(name = "username") private String username; } ``` ```xml <?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:context="http://www.springframework.org/schema/context" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd"> <context:annotation-config /> <bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean"> <property name="dataSource" ref="dataSource" /> <property name="persistenceUnitName" value="myPersistenceUnit" /> <property name="packagesToScan" value="com.example.entity" /> <property name="jpaPropertyMap"> <map> <entry key="javax.persistence.transactionType" value="RESOURCE_LOCAL" /> <entry key="javax.persistence.jtaDataSource" value="${jpa.jtaDataSource}" /> <entry key="javax.persistence.schema-generation.database.action" value="create" /> <entry key="javax.persistence.validation.mode" value="AUTO" /> </map> </property> </bean> <bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager"> <property name="entityManagerFactory" ref="entityManagerFactory" /> </bean> </beans> ``` ```java @Repository public class UserRepository { @PersistenceContext private EntityManager entityManager; public void saveUser(User user) { entityManager.persist(user); } } ```

```python pip install blinker ``` ```python from blinker import signal event_signal = signal('custom-event') @event_signal.connect def event_handler(sender): event_signal.send('CustomSender') ```