一、SQLite簡單使用

SQLite是遵循ACID的關系數據庫管理系統，它的處理速度很快，它的設計目標是嵌入式的，只需要幾百K的內存就可以了。

1.下載SQLitehttp://www.sqlite.org/download.htmlsqlite-dll-win32-x86-201410071659.zip(294.11 KiB)sqlite-shell-win32-x86-3080600.zip解壓在文件夾D:/Database/sqlite下，得到文件sqlite3.dll，sqlite3.exe參考：http://www.w3cschool.cc/sqlite/sqlite-installation.html

2.安裝SQLite寫批處理文件z_sqlite.bat，內容是：

@echod:cd D:/Database/sqlitecmd.exe

執行命令sqlite3，看到結果：

D:/Database/sqlite>sqlite3SQLite version 3.8.6 2014-08-15 11:46:33Enter ".help" for usage hints.Connected to a transient in-memory database.Use ".open FILENAME" to reopen on a persistent database.sqlite>

或是：

@echoPATH=%PATH%;D:/Database/sqlitecmd.exe

執行命令sqlite3，看到結果：

ECHO 處于打開狀態。D:/Database>PATH=C:/PRogramData/Oracle/java/javapath;D:/Program_Files/oraclexe/app/oracle/product/10.2.0/server/bin;C:/Program Files/AMD APP/bin/x86;C:/Windows/system32;C:/Windows;C:/Windows/System32/Wbem;C:/Windows/System32/WindowsPowerShell/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/sqliteD:/Database>cmd.exeMicrosoft Windows [版本 6.3.9600](c) 2013 Microsoft Corporation。保留所有權利。D:/Database>sqlite3SQLite version 3.8.6 2014-08-15 11:46:33Enter ".help" for usage hints.Connected to a transient in-memory database.Use ".open FILENAME" to reopen on a persistent database.sqlite>

表明sqlite已安裝。解釋：不讓bat文件運行命令結束后cmd窗口自動關閉，最后運行一下cmd.exe

更多疑問請參考：[SQLite 教程]：http://www.w3cschool.cc/sqlite/sqlite-installation.html

3.SQLite命令

.help　　　　幫助.show　　　顯示各種設置的當前值.schema　　 顯示建表語句

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

其它的命令類似于一搬的sql語句

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

4.SQLite管理工具：SQLiteExpert下載：http://www.sqliteexpert.com/download.html選擇免費版：SQLite Expert Personal下載的太慢了，可以選擇以前的版本：http://dl.dbank.com/c0sog1u0xb

創建db文件：

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

看到在D:/Database/sqlite目錄下生成了一個test1.db的文件File>OpenDatabase>選擇剛剛生成的db文件>確定看到數據庫的文件已經導入：

二、JPA介紹Java Persistence API：簡化現有的持久化開發工作和整合ORM技術結束現在的Hibernate、TopLink、JDO等ORM框架各自為營的局面面向Hibernate的API開發，會緊密的與Hibernate耦合JPA規范是由Hibernate的作者制定的

ORM映射元數據：　　描述對象與表之間的映射關系Java持久化API：　　 執行CRUD操作查詢語言：　　　　 JPQL，避免程序和SQL語句的緊密耦合

設置Maven4MyEclipse：MyEclipse>Maven4MyEclipse

Installation=D:/Idea/config/apache-maven-3.2.3User Settings=D:/Idea/config/apache-maven-3.2.3/conf/settings.xmlLocal Repository=D:/Idea/maven/repository

配置文件：META-INF/persistence.xmlD:/Idea/config/hibernate-release-4.3.6.Final/lib/jpa-metamodel-generator/hibernate-jpamodelgen-4.3.6.Final.jar/persistence_2_1.xsd配置數據庫的方言，以及自動建表

<?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作為Hibernate的數據源1.Maven配置文件：pom.xml用MyEclipse新建一個Maven的模塊app1.module1配置它的pom文件：/module1/pom.xml

引入JPA的依賴：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的依賴：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>

處理報錯：ArtifactTransferException: Failure to transfer org.xerial:sqlite-jdbc:jar:3.7.2 from http://zhanghua.1199.blog.163.com/blog/static/464498072013529936189/

對于這個包從maven中心傳輸到本地倉庫失敗，決定不會重新嘗試下載jar包，直到mavne再改更新索引，或強制更新。實際的解決辦法是：直接去本地倉庫，把這個1.1.1的目錄刪除掉（因為包沒有下載下來），再次刷新你的項目就中以了，或者在你的項目上右擊，選擇maven--->update就可以了，讓maven重新下載。

刪除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.xmlD:/Workspaces/IntelliJ_IDEA/JavaEE_JPA/Module1/src/main/resources/META-INF/persistence.xml在這里，需要配置數據源，數據源的位置是sqlite的db文件的位置D:/Database/sqlite/test1.db數據源的用戶名和密碼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方言復制代碼：https://code.google.com/p/hibernate-sqlite/source/browse/trunk/source/src/main/java/com/applerao/hibernatesqlite/dialect/SQLiteDialect.java?r=24修改報錯內容：http://www.myexception.cn/open-source/1120141.html

hibernate4 替代hibernate3 的Hibernate.INTEGER的用法hibernate3 中沒有了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.設置設置程序關聯：控制面板/所有控制面板項/默認程序/設置默認程序/設置程序關聯設置XML格式化代碼時不換行：MyEclipse>FilesAndEditors>XML>XML Source>Linewidth=很大的值設置JAVA格式化代碼時不換行：Java>CodeStyle>Formatter>New…>LineWrapping>SettingsForAnnotation>選擇上面的選項>LineWrapPolicy=DoNotWrap

5.異常處理

沒有持久化的提供者報錯：javax.persistence.PersistenceException: No Persistence provider for EntityManager named module1解決：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.xmlwhich 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.

執行maven clean之后

執行maven clean后會刪除運行處的persistence.xml，可以刪除再添加persistence.xml，來使persistence.xml在運行的文件夾下

四、JPA實體1.自動建表<property name="hibernate.hbm2ddl.auto" value="update" />http://www.companysz.com/talo/articles/1662244.html

validate　　　　加載hibernate時，驗證創建數據庫表結構create　　　　　每次加載hibernate，重新創建數據庫表結構，這就是導致數據庫表數據丟失的原因。create-drop　　加載hibernate時創建，退出是刪除表結構update　　　　 加載hibernate自動更新數據庫結構

需要建表的類Person.java添加注解Entity，被 @Entity注解的類就是JPA的實體類，主鍵注解 @Id， @GeneratedValuehttp://andyj.VEvb.com/blog/287827

IDENTITY：　　　表自增鍵字段，Oracle不支持這種方式AUTO： 　　　 JPA自動選擇合適的策略，是默認選項SEQUENCE：　　通過序列產生主鍵，通過 @SequenceGenerator注解指定序列名，MySql不支持這種方式TABLE：　　　　 通過表產生主鍵，框架借由表模擬序列產生主鍵，使用該策略可以使應用更易于數據庫移植

/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;@Entitypublic 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;    }}

測試類PersonTest.java

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/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中的數據庫，看到新建的表和保存的數據

2.實體類的注解

自定義表名　　　　@Table(name="xxxPerson")自定義列的屬性　　@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;    }}

刪除Person表，再次測試

日期類型　　@Temporal(TemporalType.DATE)枚舉類型　　@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;@Entitypublic class Person {    private Integer id;    private String name;    private Date birthday; //1987-12-10    private Gender gender = Gender.MAN; //默認值為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/*保存枚舉值要設置數據庫的字段不能為空*/)     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}

刪除Person表，再次測試

文件或大文本數據　　@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;@Entitypublic class Person {    private Integer id;    private String name;    private Date birthday; //1987-12-10    private Gender gender = Gender.MAN; //默認值為MAN    private String info; //存放大文本數據    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/*保存枚舉值要設置數據庫的字段不能為空*/)     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;    }}

延遲加載 　　　　　　@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;@Entitypublic class Person {    private Integer id;    private String name;    private Date birthday; //1987-12-10    private Gender gender = Gender.MAN; //默認值為MAN    private String info; //存放大文本    private byte[] file; //存放大文件，延遲加載    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/*保存枚舉值要設置數據庫的字段不能為空*/)     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) //訪問這個屬性的時候才會加載進內存    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;    }}

下面使用的實體類/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;@Entitypublic class Person {    private Integer id;    private String name;    private Date birthday; //1987-12-10    private Gender gender = Gender.MAN; //默認值為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/*保存枚舉值要設置數據庫的字段不能為空*/)     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.對實體類的查找/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); //相當于hibernate的get        Person person = em.getReference(Person.class, 1); //相當于hibernate的load//        load之后返回的是代理對象，使用的是cglib動態創建字節碼的技術//        如果不訪問數據，是不回發生數據的加載行為的//        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

異常在訪問引用對象的屬性時就會發生，即使實體管理器沒有關閉/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()); //這里出現了異常        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實體的四種狀態

new(新建)、managed(托管)、游離(脫管)、刪除當一個對象與事務關聯且進入托管狀態時對屬性進行更新，對應的數據就會同步到數據庫對象的屬性發生更改后，會放進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("老張");                em.getTransaction().commit();        em.close();        factory.close();                /**         * JPA對象的四種狀態         * new(新建)         * managed(托管)         * 游離(脫管)         * 刪除         *          * 當一個對象與事務關聯且進入托管狀態時，         * 對屬性進行更新，對應的數據就會同步到數據庫         * 對象的屬性發生更改后，會放進jdbc的批提交里去         *          */    }    }

把實體管理器中的所有實體變成游離對象　　　.clear()把游離對象同步回數據庫　　　　　　　　 .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(); //把實體管理器中的所有實體變成游離對象        person.setName("老黎");        em.merge(person); //把游離對象同步回數據庫                em.getTransaction().commit();        em.close();        factory.close();    }    }

刪除實體/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 = fa