JPA的注解的基本使用

1、persistence.xml

<?xml version="1.0" encoding="UTF-8"?>  <persistence xmlns="http://java.sun.com/xml/ns/persistence"  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"  xsi:schemaLocation="http://java.sun.com/xml/ns/persistence  http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd"  version="1.0">  <persistence-unit name="jpa" transaction-type="RESOURCE_LOCAL">  <properties>  <property name="hibernate.dialect" value="org.hibernate.dialect.Oracle10gDialect" />  <property name="hibernate.connection.driver_class" value="oracle.jdbc.driver.OracleDriver" />  <property name="hibernate.connection.username" value=" " />  <property name="hibernate.connection.password" value=" " />  <property name="hibernate.connection.url" value="jdbc:oracle:thin:@xxx.xxx.xxx.xxxx:1521:xxx" />  <property name="hibernate.max_fetch_depth" value="5" />  <property name="hibernate.jdbc.fetch_size" value="20" />  <property name="hibernate.jdbc.batch_size" value="10" />  <property name="hibernate.hbm2ddl.auto" value="update" />  <property name="hibernate.show_sql" value="true" />  <property name="hibernate.format_sql" value="false" />  </properties>  </persistence-unit> </persistence>

2 实体类

package entity;//认准是这个包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.GenerationType;import javax.persistence.Id;import javax.persistence.Lob;import javax.persistence.Table;import javax.persistence.Temporal;import javax.persistence.TemporalType;import javax.persistence.Transient;@Entity@Table(name="t_person")public class Person {private Integer id;private String name;private Date birthday;//1988-12-24private Gender gender=Gender.MAN;//设置默认值private String info;private Byte[] file;//二进制文本private String imagePath;//此无参构造器必须要有public Person() {}public Person(String name) {this.name = name;}//(strategy=GenerationType.IDENTITY)数据库id自增长的方式生成主键@Id @GeneratedValue(strategy=GenerationType.IDENTITY)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;}@Temporal(TemporalType.DATE) @Column(nullable=false)public Date getBirthday() {return birthday;}public void setBirthday(Date birthday) {this.birthday = birthday;}//@Enumerated(EnumType.ORDINAL) 此种注解在数据库中保存索引值，即0,1,2..//此种注解在数据库中保存字符串，易于理解，可读性高;     保存枚举类型时一定要设置非空约束@Enumerated(EnumType.STRING) @Column(length=5,nullable=false) public Gender getGender() {return gender;}public void setGender(Gender gender) {this.gender = gender;}@Lob   //大文本字段注解public String getInfo() {return info;}public void setInfo(String info) {this.info = info;}//@Basic(fetch=FetchType.EAGER)  代表立刻加载@Lob @Basic(fetch=FetchType.EAGER) //代表延时加载,也就是当我们不需要访问此属性时，读取时不会从数据库中抓取此属性值public Byte[] getFile() {return file;}public void setFile(Byte[] file) {this.file = file;}@Transient //不作为持久化字段，也就是说不和数据库建立映射关系public String getImagePath() {return imagePath;}public void setImagePath(String imagePath) {this.imagePath = imagePath;}}

枚举类

package entity;public enum Gender {MAN,//索引值为0WOMEN//索引值为1}

3、 测试类的测试方法

@Testpublic void mytest(){EntityManagerFactory factory = Persistence.createEntityManagerFactory("jpa");factory.close();}

4 、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/maven-v4_0_0.xsd">  <modelVersion>4.0.0</modelVersion>  <groupId>com.xxxxx.mvc</groupId>  <artifactId>jpa</artifactId>  <packaging>war</packaging>  <version>0.0.1-SNAPSHOT</version>  <name>jpa Maven Webapp</name>  <url>http://maven.apache.org</url>  <dependencies>    <dependency>      <groupId>junit</groupId>      <artifactId>junit</artifactId>      <version>4.11</version>      <scope>test</scope>    </dependency>            <dependency>  <groupId>org.hibernate</groupId>  <artifactId>hibernate-core</artifactId>  <version>3.6.8.Final</version>  <type>jar</type>  <scope>compile</scope>  </dependency>  <dependency>  <groupId>org.hibernate</groupId>  <artifactId>hibernate-annotations</artifactId>  <version>3.5.6-Final</version>  <type>jar</type>  <scope>compile</scope>  </dependency>  <dependency>  <groupId>org.hibernate</groupId>  <artifactId>hibernate-commons-annotations</artifactId>  <version>3.2.0.Final</version>  <type>jar</type>  <scope>compile</scope>  </dependency>  <!--  -->  <dependency>  <groupId>org.hibernate</groupId>  <artifactId>hibernate-entitymanager</artifactId>  <version>3.4.0.GA</version>  <type>jar</type>  </dependency>  <!-- mysql驱动  <dependency>  <groupId>mysql</groupId>  <artifactId>mysql-connector-java</artifactId>  <version>5.1.18</version>  <type>jar</type>  <scope>compile</scope>  </dependency>   -->   <!-- oracle驱动 -->  <dependency>    <groupId>com.oracle</groupId>    <artifactId>ojdbc14</artifactId>    <version>10</version></dependency>  </dependencies>  <build>    <finalName>jpa</finalName>  </build></project>