SQLite数据库和JPA简单介绍

SQLite数据库和JPA简单介绍

一、SQLite简单使用

SQLite是遵循ACID的关系数据库管理系统，它的处理速度很快，
它的设计目标是嵌入式的，只需要几百K的内存就可以了。

1.下载SQLite
http://www.sqlite.org/download.html
sqlite-dll-win32-x86-201410071659.zip(294.11 KiB)
sqlite-shell-win32-x86-3080600.zip
解压在文件夹D:\Database\sqlite下，
得到文件sqlite3.dll，sqlite3.exe

参考：http://www.w3cschool.cc/sqlite/sqlite-installation.html

2.安装SQLite
写批处理文件z_sqlite.bat，内容是：

@echo
d:
cd D:\Database\sqlite
cmd.exe

执行命令sqlite3，看到结果：

D:\Database\sqlite>sqlite3
SQLite version 3.8.6 2014-08-15 11:46:33
Enter ".help" for usage hints.
Connected to a transient in-memory database.
Use ".open FILENAME" to reopen on a persistent database.
sqlite>

或是：

@echo
PATH=%PATH%;D:\Database\sqlite
cmd.exe

执行命令sqlite3，看到结果：

ECHO 处于打开状态。

D:\Database>PATH=C:\ProgramData\Oracle\Java\javapath;D:\Program_Files\oraclexe\app\oracle\product\10.2.0\server\bin;C:\P
rogram Files\AMD APP\bin\x86;C:\Windows\system32;C:\Windows;C:\Windows\System32\Wbem;C:\Windows\System32\WindowsPowerShe
ll\v1.0\;C:\Program Files\ATI Technologies\ATI.ACE\Core-Static;C:\Python27;C:\Program Files\MySQL\MySQL Server 5.5\bin;D
:\Idea\config\apache-maven-3.2.3\bin;D:\Idea\config\apache-ant-1.9.4\bin;D:\Database\sqlite

D:\Database>cmd.exe
Microsoft Windows [版本 6.3.9600]
(c) 2013 Microsoft Corporation。保留所有权利。

D:\Database>sqlite3
SQLite version 3.8.6 2014-08-15 11:46:33
Enter ".help" for usage hints.
Connected to a transient in-memory database.
Use ".open FILENAME" to reopen on a persistent database.
sqlite>

表明sqlite已安装。
解释：不让bat文件运行命令结束后cmd窗口自动关闭，最后运行一下cmd.exe

更多疑问请参考：[SQLite 教程]：http://www.w3cschool.cc/sqlite/sqlite-installation.html

3.SQLite命令

.help 　　　　帮助
.show 　　 　 显示各种设置的当前值
.schema 　　  显示建表语句

sqlite> .schema sqlite_master
create table episodes( id integer primary key, season int, name text );

其它的命令类似于一搬的sql语句

insert into episodes values(1, 1, 'one');
select * from episodes;

4.SQLite管理工具：SQLiteExpert
下载：http://www.sqliteexpert.com/download.html
选择免费版：SQLite Expert Personal
下载的太慢了，可以选择以前的版本：
http://dl.dbank.com/c0sog1u0xb

创建db文件：

D:\Database\sqlite>sqlite3 test1.db
SQLite version 3.8.6 2014-08-15 11:46:33
Enter ".help" for usage hints.
sqlite> sqlite3 test1.db;
Error: near "sqlite3": syntax error
sqlite> 

看到在D:\Database\sqlite目录下生成了一个test1.db的文件
File>OpenDatabase>选择刚刚生成的db文件>确定
看到数据库的文件已经导入：

二、JPA介绍
Java Persistence API：简化现有的持久化开发工作和整合ORM技术
结束现在的Hibernate、TopLink、JDO等ORM框架各自为营的局面
面向Hibernate的API开发，会紧密的与Hibernate耦合
JPA规范是由Hibernate的作者制定的

ORM映射元数据：　　 描述对象与表之间的映射关系
Java持久化API：　　   执行CRUD操作
查询语言：　　　　     JPQL，避免程序和SQL语句的紧密耦合

设置Maven4MyEclipse：MyEclipse>Maven4MyEclipse

Installation=D:\Idea\config\apache-maven-3.2.3
User Settings=D:\Idea\config\apache-maven-3.2.3\conf\settings.xml
Local Repository=D:\Idea\maven\repository

配置文件：META-INF/persistence.xml
D:\Idea\config\hibernate-release-4.3.6.Final\lib\jpa-metamodel-generator
/hibernate-jpamodelgen-4.3.6.Final.jar/persistence_2_1.xsd
配置数据库的方言，以及自动建表

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.1" 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_1.xsd ">
    <persistence-unit name="module1" transaction-type="RESOURCE_LOCAL">
        <properties>
            <property name="hibernate.hbm2ddl.auto" value="update" />
            <property name="hibernate.show_sql" value="true" />
        </properties>
    </persistence-unit>
</persistence>

三、SQLite作为Hibernate的数据源
1.Maven配置文件：pom.xml
用MyEclipse新建一个Maven的模块app1.module1
配置它的pom文件：/module1/pom.xml

引入JPA的依赖：
http://hibernate.org/orm/downloads/

<!-- for JPA, use hibernate-entitymanager instead of hibernate-core -->
<dependency>
　　<groupId>org.hibernate</groupId>
　　<artifactId>hibernate-entitymanager</artifactId>
　　<version>4.3.6.Final</version>
</dependency>

sqlite-jdbc
引入sqlite的依赖：http://www.mvnrepository.com/artifact/org.xerial/sqlite-jdbc/3.7.2

<dependency>
　　<groupId>org.xerial</groupId>
　　<artifactId>sqlite-jdbc</artifactId>
　　<version>3.7.2</version>
</dependency>

处理报错：ArtifactTransferException: Failure to transfer org.xerial:sqlite-jdbc:jar:3.7.2 from
http://zhanghua.1199.blog.163.com/blog/static/464498072013529936189/

对于这个包从maven中心传输到本地仓库失败，决定不会重新尝试下载jar包，直到mavne再改更新索引，或强制更新。
实际的解决办法是：直接去本地仓库，把这个1.1.1的目录删除掉（因为包没有下载下来），再次刷新你的项目就中以了，
或者在你的项目上右击，选择maven--->update就可以了，让maven重新下载。

删除D:\Idea\maven\repository\org\xerial文件

/module1/pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>yuki.jpa.hibernate.app1</groupId>
    <artifactId>module1</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>module1</name>
    <url>http://maven.apache.org</url>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>

    <dependencies>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.11</version>
            <scope>test</scope>
        </dependency>
        <!-- for JPA, use hibernate-entitymanager instead of hibernate-core -->
        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-entitymanager</artifactId>
            <version>4.3.6.Final</version>
        </dependency>
        <dependency>
            <groupId>org.xerial</groupId>
            <artifactId>sqlite-jdbc</artifactId>
            <version>3.7.2</version>
        </dependency>

    </dependencies>
</project>

2.JPA的配置文件：persistence.xml
D:\Workspaces\IntelliJ_IDEA\JavaEE_JPA\Module1\src\main\resources\META-INF\persistence.xml
在这里，需要配置数据源，数据源的位置是sqlite的db文件的位置
D:\Database\sqlite\test1.db
数据源的用户名和密码是空字符串就可以了

/module1/src/main/java/META-INF/persistence.xml

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.1" 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_1.xsd ">
    <persistence-unit name="module1" transaction-type="RESOURCE_LOCAL">
        <class>yuki.jpa.hibernate.app1.module1.bean.Person</class>
        <properties>
            <property name="hibernate.dialect" value="com.applerao.hibernatesqlite.dialect.SQLiteDialect" />
            <property name="hibernate.hbm2ddl.auto" value="update" />
            <property name="hibernate.connection.driver_class" value="org.sqlite.JDBC" />
            <property name="hibernate.connection.url" value="jdbc:sqlite://D:/Database/sqlite/test1.db" />
            <property name="hibernate.connection.username" value="" />
            <property name="hibernate.connection.password" value="" />
            <property name="hibernate.show_sql" value="true" />
        </properties>
    </persistence-unit>
</persistence>

3.SQLite的hibernate方言
复制代码：https://code.google.com/p/hibernate-sqlite/source/browse/trunk/source/src/main/java/com/applerao/hibernatesqlite/dialect/SQLiteDialect.java?r=24
修改报错内容：http://www.myexception.cn/open-source/1120141.html

hibernate4 替代hibernate3 的Hibernate.INTEGER的用法
hibernate3 中没有了Hibernate.INTEGER的用法
在Hibernate4中使用的方法是 StandardBasicTypes.INTEGER用法
例如：sqlQuery.addScalar("id",StandardBasicTypes.INTEGER);

/module1/src/main/java/com/applerao/hibernatesqlite/dialect/SQLiteDialect.java

package com.applerao.hibernatesqlite.dialect;

/**
 * https://code.google.com/p/hibernate-sqlite/source/browse/trunk/source/src/main/java/com/applerao/hibernatesqlite/dialect/SQLiteDialect.java?r=24
 * http://www.myexception.cn/open-source/1120141.html
 *
 */

/*
 * The author disclaims copyright to this source code. In place of
 * a legal notice, here is a blessing:
 *
 * May you do good and not evil.
 * May you find forgiveness for yourself and forgive others.
 * May you share freely, never taking more than you give.
 *
 */
import java.sql.Types;

import org.hibernate.dialect.Dialect;
import org.hibernate.dialect.function.SQLFunctionTemplate;
import org.hibernate.dialect.function.StandardSQLFunction;
import org.hibernate.dialect.function.VarArgsSQLFunction;
import org.hibernate.type.StandardBasicTypes;

public class SQLiteDialect extends Dialect {
    public SQLiteDialect() {
        super();
        registerColumnType(Types.BIT, "integer");
        registerColumnType(Types.TINYINT, "tinyint");
        registerColumnType(Types.SMALLINT, "smallint");
        registerColumnType(Types.INTEGER, "integer");
        registerColumnType(Types.BIGINT, "bigint");
        registerColumnType(Types.FLOAT, "float");
        registerColumnType(Types.REAL, "real");
        registerColumnType(Types.DOUBLE, "double");
        registerColumnType(Types.NUMERIC, "numeric");
        registerColumnType(Types.DECIMAL, "decimal");
        registerColumnType(Types.CHAR, "char");
        registerColumnType(Types.VARCHAR, "varchar");
        registerColumnType(Types.LONGVARCHAR, "longvarchar");
        registerColumnType(Types.DATE, "date");
        registerColumnType(Types.TIME, "time");
        registerColumnType(Types.TIMESTAMP, "timestamp");
        registerColumnType(Types.BINARY, "blob");
        registerColumnType(Types.VARBINARY, "blob");
        registerColumnType(Types.LONGVARBINARY, "blob");
        // registerColumnType(Types.NULL, "null");
        registerColumnType(Types.BLOB, "blob");
        registerColumnType(Types.CLOB, "clob");
        registerColumnType(Types.BOOLEAN, "integer");

        registerFunction("concat", new VarArgsSQLFunction(StandardBasicTypes.STRING, "", "||", ""));
        registerFunction("mod", new SQLFunctionTemplate(StandardBasicTypes.INTEGER, "?1 % ?2"));
        registerFunction("substr", new StandardSQLFunction("substr", StandardBasicTypes.STRING));
        registerFunction("substring", new StandardSQLFunction("substr", StandardBasicTypes.STRING));
    }

    public boolean supportsIdentityColumns() {
        return true;
    }

    /*
     * public boolean supportsInsertSelectIdentity() { return true; // As
     * specify in NHibernate dialect }
     */

    public boolean hasDataTypeInIdentityColumn() {
        return false; // As specify in NHibernate dialect
    }

    /*
     * public String appendIdentitySelectToInsert(String insertString) { return
     * new StringBuffer(insertString.length()+30). // As specify in NHibernate
     * dialect append(insertString).
     * append("; ").append(getIdentitySelectString()). toString(); }
     */

    public String getIdentityColumnString() {
        // return "integer primary key autoincrement";
        return "integer";
    }

    public String getIdentitySelectString() {
        return "select last_insert_rowid()";
    }

    public boolean supportsLimit() {
        return true;
    }

    public String getLimitString(String query, boolean hasOffset) {
        return new StringBuffer(query.length() + 20).append(query).append(hasOffset ? " limit ? offset ?" : " limit ?").toString();
    }

    public boolean supportsTemporaryTables() {
        return true;
    }

    public String getCreateTemporaryTableString() {
        return "create temporary table if not exists";
    }

    public boolean dropTemporaryTableAfterUse() {
        return false;
    }

    public boolean supportsCurrentTimestampSelection() {
        return true;
    }

    public boolean isCurrentTimestampSelectStringCallable() {
        return false;
    }

    public String getCurrentTimestampSelectString() {
        return "select current_timestamp";
    }

    public boolean supportsUnionAll() {
        return true;
    }

    public boolean hasAlterTable() {
        return false; // As specify in NHibernate dialect
    }

    public boolean dropConstraints() {
        return false;
    }

    public String getAddColumnString() {
        return "add column";
    }

    public String getForUpdateString() {
        return "";
    }

    public boolean supportsOuterJoinForUpdate() {
        return false;
    }

    public String getDropForeignKeyString() {
        throw new UnsupportedOperationException("No drop foreign key syntax supported by SQLiteDialect");
    }

    public String getAddForeignKeyConstraintString(String constraintName, String[] foreignKey, String referencedTable, String[] primaryKey, boolean referencesPrimaryKey) {
        throw new UnsupportedOperationException("No add foreign key syntax supported by SQLiteDialect");
    }

    public String getAddPrimaryKeyConstraintString(String constraintName) {
        throw new UnsupportedOperationException("No add primary key syntax supported by SQLiteDialect");
    }

    public boolean supportsIfExistsBeforeTableName() {
        return true;
    }

    public boolean supportsCascadeDelete() {
        return false;
    }
}

4.设置
设置程序关联：控制面板\所有控制面板项\默认程序\设置默认程序\设置程序关联
设置XML格式化代码时不换行：
MyEclipse>FilesAndEditors>XML>XML Source>Linewidth=很大的值
设置JAVA格式化代码时不换行：
Java>CodeStyle>Formatter>New…>LineWrapping>
SettingsForAnnotation>选择上面的选项>LineWrapPolicy=DoNotWrap

5.异常处理

没有持久化的提供者
报错：javax.persistence.PersistenceException: No Persistence provider for EntityManager named module1
解决：http://stackoverflow.com/questions/21975553/javax-persistence-persistenceexception-no-persistence-provider-for-entitymanage

If you're doing this from a JUnit test, and using maven, 
the persistence.xml should be located in src/test/resources/META-INF/persistence.xml 
which will be put into the correct location at test execution time. 
The file in src/main/resources/META-INF/ is not used as it is not in the test-jar's path.

执行maven clean之后

执行maven clean后会删除运行处的persistence.xml，可以删除再添加persistence.xml，来使persistence.xml在运行的文件夹下

四、JPA实体
1.自动建表
<property name="hibernate.hbm2ddl.auto" value="update" />
http://www.cnblogs.com/talo/articles/1662244.html

validate 　　　　 加载hibernate时，验证创建数据库表结构
create 　　　　　每次加载hibernate，重新创建数据库表结构，这就是导致数据库表数据丢失的原因。
create-drop 　　 加载hibernate时创建，退出是删除表结构
update 　　　　  加载hibernate自动更新数据库结构

需要建表的类Person.java
添加注解Entity，被 @Entity注解的类就是JPA的实体类，
主键注解 @Id， @GeneratedValue
http://andyj.iteye.com/blog/287827

IDENTITY：　　　表自增键字段，Oracle不支持这种方式
AUTO： 　　　     JPA自动选择合适的策略，是默认选项
SEQUENCE：　　 通过序列产生主键，通过 @SequenceGenerator注解指定序列名，MySql不支持这种方式
TABLE：　　　　  通过表产生主键，框架借由表模拟序列产生主键，使用该策略可以使应用更易于数据库移植

/module1/src/main/java/yuki/jpa/hibernate/app1/module1/bean/person/Person1.txt

package yuki.jpa.hibernate.app1.module1.bean;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;

@Entity
public class Person {

    private Integer id;
    private String name;

    public Person() {}
    public Person(String name) {
        this.name = name;
    }

    @Id
    @GeneratedValue
    // @GeneratedValue (strategy=GenerationType.AUTO)
    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

}

测试类PersonTest.java

获取实体管理器工厂，获取实体管理器，开启事务，保存，提交事务，关闭实体管理器，关闭实体管理器工厂

/module1/src/test/java/yuki/jpa/hibernate/app1/module1/bean/personTest/PersonTest1

package yuki.jpa.hibernate.app1.module1.bean;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;

import org.junit.Test;

public class PersonTest {

    @Test
    public void save() {
        EntityManagerFactory factory = Persistence.createEntityManagerFactory("module1");
        EntityManager manager = factory.createEntityManager();
        manager.getTransaction().begin();
        manager.persist(new Person("person1"));
        manager.getTransaction().commit();
        manager.close();
        factory.close();
    }

}

刷新SQliteExpert中的数据库，看到新建的表和保存的数据

2.实体类的注解

自定义表名 　　　　@Table(name="xxxPerson")
自定义列的属性 　　@Column(length=10, nullable=false, name="personName")

/module1/src/main/java/yuki/jpa/hibernate/app1/module1/bean/person/Person2.txt

package yuki.jpa.hibernate.app1.module1.bean;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name="xxxPerson")
public class Person {

    private Integer id;
    private String name;

    public Person() {}
    public Person(String name) {
        this.name = name;
    }

    @Id
    @GeneratedValue
    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    @Column(length=10, nullable=false, name="personName")
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

}

删除Person表，再次测试

日期类型 　　@Temporal(TemporalType.DATE)
枚举类型 　　@Enumerated(EnumType.STRING)

/module1/src/main/java/yuki/jpa/hibernate/app1/module1/bean/person/Person3.txt

package yuki.jpa.hibernate.app1.module1.bean;

import java.util.Date;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.EnumType;
import javax.persistence.Enumerated;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;

@Entity
public class Person {

    private Integer id;
    private String name;
    private Date birthday; //1987-12-10
    private Gender gender = Gender.MAN; //默认值为MAN

    public Person() {}
    public Person(String name) {
        this.name = name;
    }

    @Id
    @GeneratedValue
    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }

    @Column(length=10, nullable=false)
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }

    @Temporal(TemporalType.DATE)
    public Date getBirthday() {
        return birthday;
    }
    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }

    @Enumerated(EnumType.STRING)
    @Column(length=5, nullable=false/*保存枚举值要设置数据库的字段不能为空*/)
    public Gender getGender() {
        return gender;
    }
    public void setGender(Gender gender) {
        this.gender = gender;
    }

}

/module1/src/main/java/yuki/jpa/hibernate/app1/module1/bean/Gender.java

package yuki.jpa.hibernate.app1.module1.bean;

public enum Gender {
    MAN,WOMEN
}

删除Person表，再次测试

文件或大文本数据 　　@Lob

/module1/src/main/java/yuki/jpa/hibernate/app1/module1/bean/person/Person4.txt

package yuki.jpa.hibernate.app1.module1.bean;

import java.util.Date;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.EnumType;
import javax.persistence.Enumerated;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Lob;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;

@Entity
public class Person {

    private Integer id;
    private String name;
    private Date birthday; //1987-12-10
    private Gender gender = Gender.MAN; //默认值为MAN
    private String info; //存放大文本数据
    private byte[] file; //存放文件

    public Person() {}
    public Person(String name) {
        this.name = name;
    }

    @Id
    @GeneratedValue
    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }

    @Column(length=10, nullable=false)
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }

    @Temporal(TemporalType.DATE)
    public Date getBirthday() {
        return birthday;
    }
    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }

    @Enumerated(EnumType.STRING)
    @Column(length=5, nullable=false/*保存枚举值要设置数据库的字段不能为空*/)
    public Gender getGender() {
        return gender;
    }
    public void setGender(Gender gender) {
        this.gender = gender;
    }

    @Lob
    public String getInfo() {
        return info;
    }
    public void setInfo(String info) {
        this.info = info;
    }

    @Lob
    public byte[] getFile() {
        return file;
    }
    public void setFile(byte[] file) {
        this.file = file;
    }

}

延迟加载 　　　　　　@Basic(fetch=FetchType.LAZY)
不持久化的字段 　　　@Transient

/module1/src/main/java/yuki/jpa/hibernate/app1/module1/bean/person/Person5.txt

package yuki.jpa.hibernate.app1.module1.bean;

import java.util.Date;

import javax.persistence.Basic;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.EnumType;
import javax.persistence.Enumerated;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Lob;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;
import javax.persistence.Transient;

@Entity
public class Person {

    private Integer id;
    private String name;
    private Date birthday; //1987-12-10
    private Gender gender = Gender.MAN; //默认值为MAN
    private String info; //存放大文本
    private byte[] file; //存放大文件，延迟加载
    private String imagePath; //不持久化的字段

    public Person() {}
    public Person(String name) {
        this.name = name;
    }

    @Id
    @GeneratedValue
    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }

    @Column(length=10, nullable=false)
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }

    @Temporal(TemporalType.DATE)
    public Date getBirthday() {
        return birthday;
    }
    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }

    @Enumerated(EnumType.STRING)
    @Column(length=5, nullable=false/*保存枚举值要设置数据库的字段不能为空*/)
    public Gender getGender() {
        return gender;
    }
    public void setGender(Gender gender) {
        this.gender = gender;
    }

    @Lob
    public String getInfo() {
        return info;
    }
    public void setInfo(String info) {
        this.info = info;
    }

    @Lob
    @Basic(fetch=FetchType.LAZY) //访问这个属性的时候才会加载进内存
    public byte[] getFile() {
        return file;
    }
    public void setFile(byte[] file) {
        this.file = file;
    }

    @Transient
    public String getImagePath() {
        return imagePath;
    }
    public void setImagePath(String imagePath) {
        this.imagePath = imagePath;
    }

}

下面使用的实体类
/module1/src/main/java/yuki/jpa/hibernate/app1/module1/bean/person/Person7

package yuki.jpa.hibernate.app1.module1.bean;

import java.util.Date;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.EnumType;
import javax.persistence.Enumerated;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;
import javax.persistence.Transient;

@Entity
public class Person {

    private Integer id;
    private String name;
    private Date birthday; //1987-12-10
    private Gender gender = Gender.MAN; //默认值为MAN
    private String imagePath; //不持久化的字段

    public Person() {}
    public Person(String name) {
        this.name = name;
    }

    @Id
    @GeneratedValue
    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }

    @Column(length=10, nullable=false)
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }

    @Temporal(TemporalType.DATE)
    public Date getBirthday() {
        return birthday;
    }
    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }

    @Enumerated(EnumType.STRING)
    @Column(length=5, nullable=false/*保存枚举值要设置数据库的字段不能为空*/)
    public Gender getGender() {
        return gender;
    }
    public void setGender(Gender gender) {
        this.gender = gender;
    }

    @Transient
    public String getImagePath() {
        return imagePath;
    }
    public void setImagePath(String imagePath) {
        this.imagePath = imagePath;
    }

    @Override
    public String toString() {
        return "Person [id=" + id + ", name=" + name + ", birthday=" + birthday + ", gender=" + gender + ", imagePath=" + imagePath + "]";
    }

}

3.对实体类的查找
/module1/src/test/java/yuki/jpa/hibernate/app1/module1/bean/personTest/PersonTest2

package yuki.jpa.hibernate.app1.module1.bean;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;

import org.junit.Test;

public class PersonTest {

    @Test
    public void getPerson() {
        EntityManagerFactory factory = Persistence.createEntityManagerFactory("module1");
        EntityManager em = factory.createEntityManager();
//        em.getTransaction().begin();
        Person person = em.find(Person.class, 1);
        System.out.println(person);
//        em.getTransaction().commit();
        em.close();
        factory.close();
    }

}

Hibernate: select person0_.id as id1_0_0_, person0_.birthday as birthday2_0_0_, person0_.gender as gender3_0_0_, person0_.name as name4_0_0_ from Person person0_ where person0_.id=?
Person [id=1, name=person1, birthday=null, gender=MAN, imagePath=null]

.find和.getReference
/module1/src/test/java/yuki/jpa/hibernate/app1/module1/bean/personTest/PersonTest4

package yuki.jpa.hibernate.app1.module1.bean;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;

import org.junit.Test;

public class PersonTest {

    @Test
    public void getPerson() {
        EntityManagerFactory factory = Persistence.createEntityManagerFactory("module1");
        EntityManager em = factory.createEntityManager();
//        Person person = em.find(Person.class, 1); //相当于hibernate的get
        Person person = em.getReference(Person.class, 1); //相当于hibernate的load
//        load之后返回的是代理对象，使用的是cglib动态创建字节码的技术
//        如果不访问数据，是不回发生数据的加载行为的
//        org.hibernate.LazyInitializationException: could not initialize proxy - no Session
        em.close();
        System.out.println(person.getName());
        factory.close();
    }

}

Tests run: 1, Failures: 0, Errors: 1, Skipped: 0, Time elapsed: 2.712 sec <<< FAILURE!
getPerson(yuki.jpa.hibernate.app1.module1.bean.PersonTest) Time elapsed: 2.613 sec <<< ERROR!
org.hibernate.LazyInitializationException: could not initialize proxy - no Session

异常在访问引用对象的属性时就会发生，即使实体管理器没有关闭
/module1/src/test/java/yuki/jpa/hibernate/app1/module1/bean/personTest/PersonTest5

package yuki.jpa.hibernate.app1.module1.bean;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;

import org.junit.Test;

public class PersonTest {

    @Test
    public void getPerson() {
        EntityManagerFactory factory = Persistence.createEntityManagerFactory("module1");
        EntityManager em = factory.createEntityManager();
        /*Person person = em.find(Person.class, 2);//null
        Person person = em.getReference(Person.class, 2);//javax.persistence.EntityNotFoundException
        System.out.println(person);*/
        Person person = em.getReference(Person.class, 2);
        System.out.println(person.getName()); //这里出现了异常
        em.close();
        factory.close();
    }

}

at yuki.jpa.hibernate.app1.module1.bean.Person_$$_jvst586_0.getName(Person_$$_jvst586_0.java)
at yuki.jpa.hibernate.app1.module1.bean.PersonTest.getPerson(PersonTest.java:19)

4.JPA实体的四种状态

new(新建)、managed(托管)、游离(脱管)、删除
当一个对象与事务关联且进入托管状态时
对属性进行更新，对应的数据就会同步到数据库
对象的属性发生更改后，会放进jdbc的批提交里去

/module1/src/test/java/yuki/jpa/hibernate/app1/module1/bean/personTest/PersonTest6

package yuki.jpa.hibernate.app1.module1.bean;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;

import org.junit.Test;

public class PersonTest {

    @Test
    public void updatePerson() {
        EntityManagerFactory factory = Persistence.createEntityManagerFactory("module1");
        EntityManager em = factory.createEntityManager();
        em.getTransaction().begin();

        Person person = em.find(Person.class, 2);
        person.setName("老张");

        em.getTransaction().commit();
        em.close();
        factory.close();

        /**
         * JPA对象的四种状态
         * new(新建)
         * managed(托管)
         * 游离(脱管)
         * 删除
         *
         * 当一个对象与事务关联且进入托管状态时，
         * 对属性进行更新，对应的数据就会同步到数据库
         * 对象的属性发生更改后，会放进jdbc的批提交里去
         *
         */
    }

}

把实体管理器中的所有实体变成游离对象　　　.clear()
把游离对象同步回数据库 　　　　　　　　      .merge(person)

/module1/src/test/java/yuki/jpa/hibernate/app1/module1/bean/personTest/PersonTest7

package yuki.jpa.hibernate.app1.module1.bean;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;

import org.junit.Test;

public class PersonTest {

    @Test
    public void updatePerson() {
        EntityManagerFactory factory = Persistence.createEntityManagerFactory("module1");
        EntityManager em = factory.createEntityManager();
        em.getTransaction().begin();

        Person person = em.find(Person.class, 2);
        em.clear(); //把实体管理器中的所有实体变成游离对象
        person.setName("老黎");
        em.merge(person); //把游离对象同步回数据库

        em.getTransaction().commit();
        em.close();
        factory.close();
    }

}

删除实体
/module1/src/test/java/yuki/jpa/hibernate/app1/module1/bean/personTest/PersonTest8

package yuki.jpa.hibernate.app1.module1.bean;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;

import org.junit.Test;

public class PersonTest {

    @Test
    public void deletePerson() {
        EntityManagerFactory factory = Persistence.createEntityManagerFactory("module1");
        EntityManager em = factory.createEntityManager();
        em.getTransaction().begin();

        Person person = em.find(Person.class, 2);
        em.remove(person);

        em.getTransaction().commit();
        em.close();
        factory.close();
    }

}

刷新实体

业务处理期间，有人修改了获取的数据，
这时，这个对象就不能拥有数据库中最新的数据
再次调用find方法也是不能获得最新数据的，
它会从EntityManager的一级缓存中获取刚才查询的对象
refresh可以刷新这个实体

/module1/src/test/java/yuki/jpa/hibernate/app1/module1/bean/personTest2/PersonTest4

package yuki.jpa.hibernate.app1.module1.bean;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
import javax.persistence.Query;

import org.junit.Test;

public class PersonTest {

    @Test
    public void updateQuery() {
        EntityManagerFactory factory = Persistence.createEntityManagerFactory("module1");
        EntityManager em = factory.createEntityManager();
        em.getTransaction().begin();

        Person person = em.find(Person.class, 3);
        /**
         * 业务处理期间，有人修改了获取的数据
         * 这时，这个对象就不能拥有数据库中最新的数据
         * 再次调用find方法也是不能获得最新数据的
         * 它会从EntityManager的一级缓存中获取刚才查询的对象
         * refresh可以刷新这个实体
         */
        em.refresh(person);
        System.out.println(person.getName());

        em.getTransaction().commit();
        em.close();
        factory.close();

    }

}

Hibernate: select person0_.id as id1_0_0_, person0_.birthday as birthday2_0_0_, person0_.gender as gender3_0_0_, person0_.name as name4_0_0_ from Person person0_ where person0_.id=?
Hibernate: select person0_.id as id1_0_0_, person0_.birthday as birthday2_0_0_, person0_.gender as gender3_0_0_, person0_.name as name4_0_0_ from Person person0_ where person0_.id=?
person1

5.JPQL语句

用hibernate实现的JPA是可以不写select o的,建议写上select o，因为这是JPA的规范
写据查询语句参数的时候，不要把参数直接放进去
这样会造成字符串的组拼，delete from table_name会删除所有的表的数据
可以使用命名参数，比如:id；也可以使用位参，比如?；
位参可以设置编号，在问号后写1：?1，表示从1开始

/module1/src/test/java/yuki/jpa/hibernate/app1/module1/bean/personTest2/PersonTest1

package yuki.jpa.hibernate.app1.module1.bean;

import java.util.List;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
import javax.persistence.Query;

import org.junit.Test;

public class PersonTest {

    @Test
    public void queryPerson() {
        EntityManagerFactory factory = Persistence.createEntityManagerFactory("module1");
        EntityManager em = factory.createEntityManager();
        /**
         * 用hibernate实现的JPA是可以不写select o的
         * 建议写上select o，因为这是JPA的规范
         *
         * 写据查询语句参数的时候，不要把参数直接放进去
         * 这样会造成字符串的组拼，delete from table_name会删除所有的表的数据
         * 可以使用命名参数，比如:id；也可以使用位参，比如?；
         * 位参可以设置编号，在问号后写1：?1，表示从1开始
         *
         */
//        Query query = em.createQuery("select count(o) from Person o");
        Query query = em.createQuery("select o from Person o where o.id=?1");
        query.setParameter(1, 2);
//        Person person = (Person) query.getSingleResult();
//        System.out.println(person.getName());
        @SuppressWarnings("unchecked")
        List<Person> persons = query.getResultList();
        for(Person p : persons)
            System.out.println(p.getName());

        em.close();
        factory.close();

    }

}

Hibernate: select person0_.id as id1_0_, person0_.birthday as birthday2_0_, person0_.gender as gender3_0_, person0_.name as name4_0_ from Person person0_ where person0_.id=?
person1

增删改操作需要开启事务，如果不开启会抛出异常

/module1/src/test/java/yuki/jpa/hibernate/app1/module1/bean/personTest2/PersonTest2

package yuki.jpa.hibernate.app1.module1.bean;

import java.util.List;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
import javax.persistence.Query;

import org.junit.Test;

public class PersonTest {

    @Test
    public void deleteQuery() {
        EntityManagerFactory factory = Persistence.createEntityManagerFactory("module1");
        EntityManager em = factory.createEntityManager();
//        如果不开启事务
//        javax.persistence.TransactionRequiredException: Executing an update/delete query
        em.getTransaction().begin();

        Query query = em.createQuery("delete from Person o where o.id=?1");
        query.setParameter(1, 2);
        query.executeUpdate();

        em.getTransaction().commit();
        em.close();
        factory.close();

    }

}

javax.persistence.TransactionRequiredException: Executing an update/delete query
/module1/src/test/java/yuki/jpa/hibernate/app1/module1/bean/personTest2/PersonTest2
Hibernate: delete from Person where id=?

/module1/src/test/java/yuki/jpa/hibernate/app1/module1/bean/personTest2/PersonTest3

package yuki.jpa.hibernate.app1.module1.bean;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
import javax.persistence.Query;

import org.junit.Test;

public class PersonTest {

    @Test
    public void updateQuery() {
        EntityManagerFactory factory = Persistence.createEntityManagerFactory("module1");
        EntityManager em = factory.createEntityManager();
//        如果不开启事务
//        javax.persistence.TransactionRequiredException: Executing an update/delete query
        em.getTransaction().begin();

        Query query = em.createQuery("update Person o set o.name=:name where o.id=:id");
        query.setParameter("name", "name3");
        query.setParameter("id", 3);
        query.executeUpdate();

        em.getTransaction().commit();
        em.close();
        factory.close();

    }

}

/module1/src/test/java/yuki/jpa/hibernate/app1/module1/bean/personTest2/PersonTest3
Hibernate: update Person set name=? where id=?

五、"JPA并不依赖于某一个持久化产品"的解释
创建实体管理工厂：Persistence.createEntityManagerFactory
寻找类路径下所有的持久化驱动类，JPA并不依赖于某一个持久化产品
如何与持久化产品进行对接，使用的是类似于JDBC驱动的一个类
这个类在jdbc里叫做jdbc驱动，在持久化里叫做持久化驱动类

/META-INF/services/下寻找：javax.persistence.spi.PersistenceProvider
找到指定的持久化驱动，这个文件起到了桥梁的作用

org.hibernate.jpa.HibernatePersistenceProvider
# The deprecated provider, logs warnings when used.
org.hibernate.ejb.HibernatePersistence

遍历所有的驱动，具体使用哪一个具有随机性
如果创建出了EntityManagerFactory对象，就跳出循环
/module1/src/test/java/yuki/jpa/hibernate/app1/module1/bean/persistence/Persistence.java

/*
 * Copyright (c) 2008, 2009, 2011 Oracle, Inc. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v1.0 and Eclipse Distribution License v. 1.0
 * which accompanies this distribution.  The Eclipse Public License is available
 * at http://www.eclipse.org/legal/epl-v10.html and the Eclipse Distribution License
 * is available at http://www.eclipse.org/org/documents/edl-v10.php.
 */
//package javax.persistence;
package yuki.jpa.hibernate.app1.module1.bean.persistence;

import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;

import javax.persistence.EntityManagerFactory;
import javax.persistence.PersistenceException;
import javax.persistence.PersistenceUtil;
import javax.persistence.spi.LoadState;
import javax.persistence.spi.PersistenceProvider;
import javax.persistence.spi.PersistenceProviderResolverHolder;

/**
 * Bootstrap class that provides access to an EntityManagerFactory.
 */
public class Persistence {

    @Deprecated
    public static final String PERSISTENCE_PROVIDER = "javax.persistence.spi.PeristenceProvider";

    @Deprecated
    protected static final Set<PersistenceProvider> providers = new HashSet<PersistenceProvider>();

    /**
     * Create and return an EntityManagerFactory for the named persistence unit.
     *
     * @param persistenceUnitName The name of the persistence unit
     *
     * @return The factory that creates EntityManagers configured according to the specified persistence unit
     */
    /// 一开始调用的方法
    public static EntityManagerFactory createEntityManagerFactory(String persistenceUnitName) {
        return createEntityManagerFactory( persistenceUnitName, null );
    }

    /**
     * Create and return an EntityManagerFactory for the named persistence unit using the given properties.
     *
     * @param persistenceUnitName The name of the persistence unit
     * @param properties Additional properties to use when creating the factory. The values of these properties override
     * any values that may have been configured elsewhere
     *
     * @return The factory that creates EntityManagers configured according to the specified persistence unit
     */
    // 被一开始调用的方法指向的方法
    public static EntityManagerFactory createEntityManagerFactory(String persistenceUnitName, @SuppressWarnings("rawtypes") Map properties) {
        EntityManagerFactory emf = null;
        /**
         * 寻找类路径下所有的持久化驱动类，JPA并不依赖于某一个持久化产品
         * 如何与持久化产品进行对接，使用的是类似于JDBC驱动的一个类
         * 这个类在jdbc里叫做jdbc驱动，在持久化里叫做持久化驱动类
         *
         * D:\Idea\maven\repository\org\hibernate\hibernate-entitymanager\4.3.6.Final\hibernate-entitymanager-4.3.6.Final.jar
         * 寻找hibernate-entitymanager-4.3.6.Final.jar/META-INF/services/javax.persistence.spi.PersistenceProvider
//                org.hibernate.jpa.HibernatePersistenceProvider
//                # The deprecated provider, logs warnings when used.
//                org.hibernate.ejb.HibernatePersistence
         * 找到指定的持久化驱动，这个文件起到了桥梁的作用
         *
         */
        List<PersistenceProvider> providers = getProviders();
        /**
         * 遍历所有的驱动，具体使用哪一个具有随机性
         * 如果创建出了EntityManagerFactory对象，就跳出循环
         */
        for ( PersistenceProvider provider : providers ) {
            emf = provider.createEntityManagerFactory( persistenceUnitName, properties );
            if ( emf != null ) {
                break;
            }
        }
        if ( emf == null ) {
            throw new PersistenceException( "No Persistence provider for EntityManager named " + persistenceUnitName );
        }
        return emf;
    }

    private static List<PersistenceProvider> getProviders() {
        return PersistenceProviderResolverHolder
                .getPersistenceProviderResolver()
                .getPersistenceProviders();
    }

    /**
     * Create database schemas and/or tables and/or create DDL scripts as determined by the supplied properties
     *
     * Called when schema generation is to occur as a separate phase from creation of the entity manager factory.
     *
     * @param persistenceUnitName the name of the persistence unit
     * @param properties properties for schema generation; these may also contain provider-specific properties. The
     * values of these properties override any values that may have been configured elsewhere.
     *
     * @throws PersistenceException if insufficient or inconsistent configuration information is provided or if schema
     * generation otherwise fails.
     */
    public static void generateSchema(String persistenceUnitName, @SuppressWarnings("rawtypes") Map properties) {
        List<PersistenceProvider> providers = getProviders();
        for ( PersistenceProvider provider : providers ) {
            final boolean generated = provider.generateSchema( persistenceUnitName, properties );
            if ( generated ) {
                return;
            }
        }

        throw new PersistenceException(
                "No persistence provider found for schema generation for persistence-unit named " + persistenceUnitName
        );
    }

    /**
     * @return Returns a <code>PersistenceUtil</code> instance.
     */
    public static PersistenceUtil getPersistenceUtil() {
        return util;
    }

    private static PersistenceUtil util =
            //TODO add an Hibernate specific optimization
        new PersistenceUtil() {
            public boolean isLoaded(Object entity, String attributeName) {
                List<PersistenceProvider> providers = Persistence.getProviders();
                for ( PersistenceProvider provider : providers ) {
                    final LoadState state = provider.getProviderUtil().isLoadedWithoutReference( entity, attributeName );
                    if ( state == LoadState.UNKNOWN ) continue;
                    return state == LoadState.LOADED;
                }
                for ( PersistenceProvider provider : providers ) {
                    final LoadState state = provider.getProviderUtil().isLoadedWithReference( entity, attributeName );
                    if ( state == LoadState.UNKNOWN ) continue;
                    return state == LoadState.LOADED;
                }
                return true;
            }

            public boolean isLoaded(Object object) {
                List<PersistenceProvider> providers = Persistence.getProviders();
                for ( PersistenceProvider provider : providers ) {
                    final LoadState state = provider.getProviderUtil().isLoaded( object );
                    if ( state == LoadState.UNKNOWN ) continue;
                    return state == LoadState.LOADED;
                }
                return true;
            }
        };
}

目录结构：

更多详情请参考[黎活明JPA教程]：http://www.itcast.cn/news/c8cd98d0/3d09/443f/a189/904fccafbd72.shtml

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孔東陽
2014/10/12