JPA雖然是Java EE規范的一部分，但是可以在J2SE環境下單獨使用，不需要Web相關容器。本篇主要通過Netbeans 自動生成的代碼來學習JPA相關內容。

1.打開Netbeans 8.1 添加Mysql數據庫連接

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2.新建Java應用程式，輸入項目名稱JpaExample

3.在項目中右鍵新建其他，選擇主樣例窗體/詳細樣例窗體，輸入類名稱和包名稱

4.選擇第一步建立的數據庫連接->選擇表(user)，右側為程式中用到的欄位，默認是全部帶到右邊，不需要的可以移到左邊

5.選擇在Swing界面上顯示的欄位，默認全部在右邊表示全選，不需要的可以移到左邊。點擊完成

6.查看生成的類，persistence.xml是jpa配置文件，User.java是對于table的實體，MasterDetailForm.java是自動生成的Swing界面，自動添加的庫文件包括實現JPA2.1 的EclipseLink和添加連接mysql數據庫的jdbc驅動，都是安裝Netbeans自帶的可以自行替換指定版本。?

7.運行，點擊New就可以新增內容，Delete刪除上面Jtable選中的數據，Save保存到數據庫，Refresh 刷新數據，主要是數據庫數據與JPA同步，如果數據庫有變動，刷新后本地JPA顯示變動后數據。

8.代碼分析,完整MasterDetailForm.java如下。

package com.cc.jpa;import java.awt.EventQueue; import java.beans.Beans; import java.util.ArrayList; import java.util.List; import javax.persistence.RollbackException; import javax.swing.JFrame; import javax.swing.JPanel;/**** @author dev*/ public class MasterDetailForm extends JPanel {public MasterDetailForm() {initComponents();if (!Beans.isDesignTime()) {entityManager.getTransaction().begin();}}/*** This method is called from within the constructor to initialize the form.* WARNING: Do NOT modify this code. The content of this method is always* regenerated by the Form Editor.*/@SuppressWarnings("unchecked")// <editor-fold defaultstate="collapsed" desc="Generated Code"> private void initComponents() {bindingGroup = new org.jdesktop.beansbinding.BindingGroup();entityManager = java.beans.Beans.isDesignTime() ? null : javax.persistence.Persistence.createEntityManagerFactory("ccPU").createEntityManager();query = java.beans.Beans.isDesignTime() ? null : entityManager.createQuery("SELECT u FROM User u");list = java.beans.Beans.isDesignTime() ? java.util.Collections.emptyList() : org.jdesktop.observablecollections.ObservableCollections.observableList(query.getResultList());masterScrollPane = new javax.swing.JScrollPane();masterTable = new javax.swing.JTable();idLabel = new javax.swing.JLabel();usernmaeLabel = new javax.swing.JLabel();passwordLabel = new javax.swing.JLabel();nameLabel = new javax.swing.JLabel();idField = new javax.swing.JTextField();usernmaeField = new javax.swing.JTextField();passwordField = new javax.swing.JTextField();nameField = new javax.swing.JTextField();saveButton = new javax.swing.JButton();refreshButton = new javax.swing.JButton();newButton = new javax.swing.JButton();deleteButton = new javax.swing.JButton();FormListener formListener = new FormListener();org.jdesktop.swingbinding.JTableBinding jTableBinding = org.jdesktop.swingbinding.SwingBindings.createJTableBinding(org.jdesktop.beansbinding.AutoBinding.UpdateStrategy.READ_WRITE, list, masterTable);org.jdesktop.swingbinding.JTableBinding.ColumnBinding columnBinding = jTableBinding.addColumnBinding(org.jdesktop.beansbinding.ELProperty.create("${id}"));columnBinding.setColumnName("Id");columnBinding.setColumnClass(Integer.class);columnBinding = jTableBinding.addColumnBinding(org.jdesktop.beansbinding.ELProperty.create("${usernmae}"));columnBinding.setColumnName("Usernmae");columnBinding.setColumnClass(String.class);columnBinding = jTableBinding.addColumnBinding(org.jdesktop.beansbinding.ELProperty.create("${password}"));columnBinding.setColumnName("Password");columnBinding.setColumnClass(String.class);columnBinding = jTableBinding.addColumnBinding(org.jdesktop.beansbinding.ELProperty.create("${name}"));columnBinding.setColumnName("Name");columnBinding.setColumnClass(String.class);bindingGroup.addBinding(jTableBinding);masterScrollPane.setViewportView(masterTable);idLabel.setText("Id:");usernmaeLabel.setText("Usernmae:");passwordLabel.setText("Password:");nameLabel.setText("Name:");org.jdesktop.beansbinding.Binding binding = org.jdesktop.beansbinding.Bindings.createAutoBinding(org.jdesktop.beansbinding.AutoBinding.UpdateStrategy.READ_WRITE, masterTable, org.jdesktop.beansbinding.ELProperty.create("${selectedElement.id}"), idField, org.jdesktop.beansbinding.BeanProperty.create("text"));binding.setSourceUnreadableValue("null");bindingGroup.addBinding(binding);binding = org.jdesktop.beansbinding.Bindings.createAutoBinding(org.jdesktop.beansbinding.AutoBinding.UpdateStrategy.READ, masterTable, org.jdesktop.beansbinding.ELProperty.create("${selectedElement != null}"), idField, org.jdesktop.beansbinding.BeanProperty.create("enabled"));bindingGroup.addBinding(binding);binding = org.jdesktop.beansbinding.Bindings.createAutoBinding(org.jdesktop.beansbinding.AutoBinding.UpdateStrategy.READ_WRITE, masterTable, org.jdesktop.beansbinding.ELProperty.create("${selectedElement.usernmae}"), usernmaeField, org.jdesktop.beansbinding.BeanProperty.create("text"));binding.setSourceUnreadableValue("null");bindingGroup.addBinding(binding);binding = org.jdesktop.beansbinding.Bindings.createAutoBinding(org.jdesktop.beansbinding.AutoBinding.UpdateStrategy.READ, masterTable, org.jdesktop.beansbinding.ELProperty.create("${selectedElement != null}"), usernmaeField, org.jdesktop.beansbinding.BeanProperty.create("enabled"));bindingGroup.addBinding(binding);binding = org.jdesktop.beansbinding.Bindings.createAutoBinding(org.jdesktop.beansbinding.AutoBinding.UpdateStrategy.READ_WRITE, masterTable, org.jdesktop.beansbinding.ELProperty.create("${selectedElement.password}"), passwordField, org.jdesktop.beansbinding.BeanProperty.create("text"));binding.setSourceUnreadableValue("null");bindingGroup.addBinding(binding);binding = org.jdesktop.beansbinding.Bindings.createAutoBinding(org.jdesktop.beansbinding.AutoBinding.UpdateStrategy.READ, masterTable, org.jdesktop.beansbinding.ELProperty.create("${selectedElement != null}"), passwordField, org.jdesktop.beansbinding.BeanProperty.create("enabled"));bindingGroup.addBinding(binding);binding = org.jdesktop.beansbinding.Bindings.createAutoBinding(org.jdesktop.beansbinding.AutoBinding.UpdateStrategy.READ_WRITE, masterTable, org.jdesktop.beansbinding.ELProperty.create("${selectedElement.name}"), nameField, org.jdesktop.beansbinding.BeanProperty.create("text"));binding.setSourceUnreadableValue("null");bindingGroup.addBinding(binding);binding = org.jdesktop.beansbinding.Bindings.createAutoBinding(org.jdesktop.beansbinding.AutoBinding.UpdateStrategy.READ, masterTable, org.jdesktop.beansbinding.ELProperty.create("${selectedElement != null}"), nameField, org.jdesktop.beansbinding.BeanProperty.create("enabled"));bindingGroup.addBinding(binding);saveButton.setText("Save");saveButton.addActionListener(formListener);refreshButton.setText("Refresh");refreshButton.addActionListener(formListener);newButton.setText("New");newButton.addActionListener(formListener);deleteButton.setText("Delete");binding = org.jdesktop.beansbinding.Bindings.createAutoBinding(org.jdesktop.beansbinding.AutoBinding.UpdateStrategy.READ, masterTable, org.jdesktop.beansbinding.ELProperty.create("${selectedElement != null}"), deleteButton, org.jdesktop.beansbinding.BeanProperty.create("enabled"));bindingGroup.addBinding(binding);deleteButton.addActionListener(formListener);javax.swing.GroupLayout layout = new javax.swing.GroupLayout(this);this.setLayout(layout);layout.setHorizontalGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING).addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup().addComponent(newButton).addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED).addComponent(deleteButton).addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED).addComponent(refreshButton).addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED).addComponent(saveButton).addContainerGap()).addGroup(layout.createSequentialGroup().addContainerGap().addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING).addComponent(idLabel).addComponent(usernmaeLabel).addComponent(passwordLabel).addComponent(nameLabel)).addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED).addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING).addComponent(idField, javax.swing.GroupLayout.DEFAULT_SIZE, 315, Short.MAX_VALUE).addComponent(usernmaeField, javax.swing.GroupLayout.DEFAULT_SIZE, 315, Short.MAX_VALUE).addComponent(passwordField, javax.swing.GroupLayout.DEFAULT_SIZE, 315, Short.MAX_VALUE).addComponent(nameField, javax.swing.GroupLayout.DEFAULT_SIZE, 315, Short.MAX_VALUE)).addContainerGap()).addGroup(layout.createSequentialGroup().addContainerGap().addComponent(masterScrollPane, javax.swing.GroupLayout.DEFAULT_SIZE, 380, Short.MAX_VALUE).addContainerGap()));layout.linkSize(javax.swing.SwingConstants.HORIZONTAL, new java.awt.Component[] {deleteButton, newButton, refreshButton, saveButton});layout.setVerticalGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING).addGroup(layout.createSequentialGroup().addContainerGap().addComponent(masterScrollPane, javax.swing.GroupLayout.DEFAULT_SIZE, 130, Short.MAX_VALUE).addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED).addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE).addComponent(idLabel).addComponent(idField, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)).addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED).addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE).addComponent(usernmaeLabel).addComponent(usernmaeField, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)).addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED).addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE).addComponent(passwordLabel).addComponent(passwordField, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)).addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED).addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE).addComponent(nameLabel).addComponent(nameField, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)).addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED).addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE).addComponent(saveButton).addComponent(refreshButton).addComponent(deleteButton).addComponent(newButton)).addContainerGap()));bindingGroup.bind();}// Code for dispatching events from components to event handlers.private class FormListener implements java.awt.event.ActionListener {FormListener() {}public void actionPerformed(java.awt.event.ActionEvent evt) {if (evt.getSource() == saveButton) {MasterDetailForm.this.saveButtonActionPerformed(evt);}else if (evt.getSource() == refreshButton) {MasterDetailForm.this.refreshButtonActionPerformed(evt);}else if (evt.getSource() == newButton) {MasterDetailForm.this.newButtonActionPerformed(evt);}else if (evt.getSource() == deleteButton) {MasterDetailForm.this.deleteButtonActionPerformed(evt);}}}// </editor-fold> @SuppressWarnings("unchecked")private void refreshButtonActionPerformed(java.awt.event.ActionEvent evt) { entityManager.getTransaction().rollback();entityManager.getTransaction().begin();java.util.Collection data = query.getResultList();for (Object entity : data) {entityManager.refresh(entity);}list.clear();list.addAll(data);} private void deleteButtonActionPerformed(java.awt.event.ActionEvent evt) { int[] selected = masterTable.getSelectedRows();List<com.cc.jpa.User> toRemove = new ArrayList<com.cc.jpa.User>(selected.length);for (int idx = 0; idx < selected.length; idx++) {com.cc.jpa.User u = list.get(masterTable.convertRowIndexToModel(selected[idx]));toRemove.add(u);entityManager.remove(u);}list.removeAll(toRemove);} private void newButtonActionPerformed(java.awt.event.ActionEvent evt) { com.cc.jpa.User u = new com.cc.jpa.User();entityManager.persist(u);list.add(u);int row = list.size() - 1;masterTable.setRowSelectionInterval(row, row);masterTable.scrollRectToVisible(masterTable.getCellRect(row, 0, true));} private void saveButtonActionPerformed(java.awt.event.ActionEvent evt) { try {entityManager.getTransaction().commit();entityManager.getTransaction().begin();} catch (RollbackException rex) {rex.printStackTrace();entityManager.getTransaction().begin();List<com.cc.jpa.User> merged = new ArrayList<com.cc.jpa.User>(list.size());for (com.cc.jpa.User u : list) {merged.add(entityManager.merge(u));}list.clear();list.addAll(merged);}} // Variables declaration - do not modify private javax.swing.JButton deleteButton;private javax.persistence.EntityManager entityManager;private javax.swing.JTextField idField;private javax.swing.JLabel idLabel;private java.util.List<com.cc.jpa.User> list;private javax.swing.JScrollPane masterScrollPane;private javax.swing.JTable masterTable;private javax.swing.JTextField nameField;private javax.swing.JLabel nameLabel;private javax.swing.JButton newButton;private javax.swing.JTextField passwordField;private javax.swing.JLabel passwordLabel;private javax.persistence.Query query;private javax.swing.JButton refreshButton;private javax.swing.JButton saveButton;private javax.swing.JTextField usernmaeField;private javax.swing.JLabel usernmaeLabel;private org.jdesktop.beansbinding.BindingGroup bindingGroup;// End of variables declaration public static void main(String[] args) {/* Set the Nimbus look and feel *///<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">/* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.* For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html */try {for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {if ("Nimbus".equals(info.getName())) {javax.swing.UIManager.setLookAndFeel(info.getClassName());break;}}} catch (ClassNotFoundException ex) {java.util.logging.Logger.getLogger(MasterDetailForm.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);} catch (InstantiationException ex) {java.util.logging.Logger.getLogger(MasterDetailForm.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);} catch (IllegalAccessException ex) {java.util.logging.Logger.getLogger(MasterDetailForm.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);} catch (javax.swing.UnsupportedLookAndFeelException ex) {java.util.logging.Logger.getLogger(MasterDetailForm.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);}//</editor-fold>/* Create and display the form */EventQueue.invokeLater(new Runnable() {public void run() {JFrame frame = new JFrame();frame.setContentPane(new MasterDetailForm());frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);frame.pack();frame.setVisible(true);}});}} View Code

主要部分:

entityManager初始化，ccPU是在persistence.xml中定義的persistence-unit 的名稱， query 和list的 代碼 一個是新建一個查詢，另一個是查出所有資料。query其實可以用另一種寫法，使用entityManager.createNamedQuery("User.findAll");

查看User.java文件會發現，Netbeans 生成的文件里面默認生成了幾個Query，也可以根據需要自行添加，集中管理。

entityManager = java.beans.Beans.isDesignTime() ? null : javax.persistence.Persistence.createEntityManagerFactory("ccPU").createEntityManager(); query = java.beans.Beans.isDesignTime() ? null : entityManager.createQuery("SELECT u FROM User u"); list = java.beans.Beans.isDesignTime() ? java.util.Collections.emptyList() : org.jdesktop.observablecollections.ObservableCollections.observableList(query.getResultList());

User:

/** To change this license header, choose License Headers in Project Properties.* To change this template file, choose Tools | Templates* and open the template in the editor.*/ package com.cc.jpa;import java.beans.PropertyChangeListener; import java.beans.PropertyChangeSupport; import java.io.Serializable; import javax.persistence.Basic; import javax.persistence.Column; import javax.persistence.Entity; import javax.persistence.Id; import javax.persistence.NamedQueries; import javax.persistence.NamedQuery; import javax.persistence.Table; import javax.persistence.Transient;/**** @author dev*/ @Entity @Table(name = "user", catalog = "cc", schema = "") @NamedQueries({@NamedQuery(name = "User.findAll", query = "SELECT u FROM User u"),@NamedQuery(name = "User.findById", query = "SELECT u FROM User u WHERE u.id = :id"),@NamedQuery(name = "User.findByUsernmae", query = "SELECT u FROM User u WHERE u.usernmae = :usernmae"),@NamedQuery(name = "User.findByPassword", query = "SELECT u FROM User u WHERE u.password = :password"),@NamedQuery(name = "User.findByName", query = "SELECT u FROM User u WHERE u.name = :name")}) public class User implements Serializable {@Transientprivate PropertyChangeSupport changeSupport = new PropertyChangeSupport(this);private static final long serialVersionUID = 1L;@Id@Basic(optional = false)@Column(name = "id")private Integer id;@Basic(optional = false)@Column(name = "usernmae")private String usernmae;@Basic(optional = false)@Column(name = "password")private String password;@Basic(optional = false)@Column(name = "name")private String name;public User() {}public User(Integer id) {this.id = id;}public User(Integer id, String usernmae, String password, String name) {this.id = id;this.usernmae = usernmae;this.password = password;this.name = name;}public Integer getId() {return id;}public void setId(Integer id) {Integer oldId = this.id;this.id = id;changeSupport.firePropertyChange("id", oldId, id);}public String getUsernmae() {return usernmae;}public void setUsernmae(String usernmae) {String oldUsernmae = this.usernmae;this.usernmae = usernmae;changeSupport.firePropertyChange("usernmae", oldUsernmae, usernmae);}public String getPassword() {return password;}public void setPassword(String password) {String oldPassword = this.password;this.password = password;changeSupport.firePropertyChange("password", oldPassword, password);}public String getName() {return name;}public void setName(String name) {String oldName = this.name;this.name = name;changeSupport.firePropertyChange("name", oldName, name);}@Overridepublic int hashCode() {int hash = 0;hash += (id != null ? id.hashCode() : 0);return hash;}@Overridepublic boolean equals(Object object) {// TODO: Warning - this method won't work in the case the id fields are not setif (!(object instanceof User)) {return false;}User other = (User) object;if ((this.id == null && other.id != null) || (this.id != null && !this.id.equals(other.id))) {return false;}return true;}@Overridepublic String toString() {return "com.cc.jpa.User[ id=" + id + " ]";}public void addPropertyChangeListener(PropertyChangeListener listener) {changeSupport.addPropertyChangeListener(listener);}public void removePropertyChangeListener(PropertyChangeListener listener) {changeSupport.removePropertyChangeListener(listener);}} View Code

New，主要是新增一個新的User對象，沒有寫到數據庫中，主要是前端操作

com.cc.jpa.User u = new com.cc.jpa.User(); entityManager.persist(u); list.add(u); int row = list.size() - 1; masterTable.setRowSelectionInterval(row, row); masterTable.scrollRectToVisible(masterTable.getCellRect(row, 0, true));

Delete，執行entityManager.remove(u)并沒有寫到數據庫是因為有開啟Transaction ，在保存的時候才會commit

int[] selected = masterTable.getSelectedRows();
List<com.cc.jpa.User> toRemove = new ArrayList<com.cc.jpa.User>(selected.length);for (int idx = 0; idx < selected.length; idx++) {com.cc.jpa.User u = list.get(masterTable.convertRowIndexToModel(selected[idx]));toRemove.add(u);entityManager.remove(u);}list.removeAll(toRemove);

Save，主要就是Transaction 的提交以及異常處理

try {
entityManager.getTransaction().commit();
entityManager.getTransaction().begin();
} catch (RollbackException rex) {
rex.printStackTrace();
entityManager.getTransaction().begin();
List<com.cc.jpa.User> merged = new ArrayList<com.cc.jpa.User>(list.size());
for (com.cc.jpa.User u : list) {
merged.add(entityManager.merge(u));
}
list.clear();
list.addAll(merged);
}

Refresh，同步數據庫數據

entityManager.getTransaction().rollback(); entityManager.getTransaction().begin(); java.util.Collection data = query.getResultList(); for (Object entity : data) {entityManager.refresh(entity); } list.clear(); list.addAll(data);

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此范例主要是J2SE 下JPA的使用，實際項目中，可能設計很多table，程式也會相應的分層，如果只是學習一下JPA的特性熟悉下方法，這種方式也是沒問題的。使用eclipse 創建JPA時?EclipseLink 需要單獨下載，EclipseLink 前身是Oracle TopLink ，以前商業框架 ADF的一部分，用JPA 選擇EclipseLink ，Hibernate 或其他實現都沒有關系，而且只用JPA的功能，不用實現提供的一些擴展的話，切換使用都是沒有問題的，就像JSP頁面用不同的容器，Tomcat、Jetty、GlassFish結果是沒差別的。

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轉載于:https://www.cnblogs.com/NZuoF/p/5558826.html

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