Spring-Data-JPA高级

一、为什么使用Spring Data JPA

Spring Data JPA 让我们解脱了DAO层的操作，基本上所有CRUD都可以依赖于它来实现,在实际的工作工程中，推荐使用Spring Data JPA + ORM（如：hibernate）完成操作，这样在切换不同的ORM框架时提供了极大的方便，同时也使数据库层操作更加简单，方便解耦。

二、完成简单CRUD操作

2.1搭建开发环境

2.1.1pom坐标

 <properties>
        <spring.version>4.2.4.RELEASEspring.version>
        <hibernate.version>5.0.7.Finalhibernate.version>
        <slf4j.version>1.6.6slf4j.version>
        <log4j.version>1.2.12log4j.version>
        <c3p0.version>0.9.1.2c3p0.version>
        <mysql.version>5.1.6mysql.version>
    properties>

    <dependencies>
        
        <dependency>
            <groupId>junitgroupId>
            <artifactId>junitartifactId>
            <version>4.9version>
            <scope>testscope>
        dependency>
        
        
        <dependency>
            <groupId>org.aspectjgroupId>
            <artifactId>aspectjweaverartifactId>
            <version>1.6.8version>
        dependency>

        <dependency>
            <groupId>org.springframeworkgroupId>
            <artifactId>spring-aopartifactId>
            <version>${spring.version}version>
        dependency>

        <dependency>
            <groupId>org.springframeworkgroupId>
            <artifactId>spring-contextartifactId>
            <version>${spring.version}version>
        dependency>

        <dependency>
            <groupId>org.springframeworkgroupId>
            <artifactId>spring-context-supportartifactId>
            <version>${spring.version}version>
        dependency>

        <dependency>
            <groupId>org.springframeworkgroupId>
            <artifactId>spring-ormartifactId>
            <version>${spring.version}version>
        dependency>

        <dependency>
            <groupId>org.springframeworkgroupId>
            <artifactId>spring-beansartifactId>
            <version>${spring.version}version>
        dependency>

        <dependency>
            <groupId>org.springframeworkgroupId>
            <artifactId>spring-coreartifactId>
            <version>${spring.version}version>
        dependency>
        
        

        
        <dependency>
            <groupId>org.hibernategroupId>
            <artifactId>hibernate-coreartifactId>
            <version>${hibernate.version}version>
        dependency>
        <dependency>
            <groupId>org.hibernategroupId>
            <artifactId>hibernate-entitymanagerartifactId>
            <version>${hibernate.version}version>
        dependency>
        <dependency>
            <groupId>org.hibernategroupId>
            <artifactId>hibernate-validatorartifactId>
            <version>5.2.1.Finalversion>
        dependency>
        

        
        <dependency>
            <groupId>c3p0groupId>
            <artifactId>c3p0artifactId>
            <version>${c3p0.version}version>
        dependency>
        

        
        <dependency>
            <groupId>log4jgroupId>
            <artifactId>log4jartifactId>
            <version>${log4j.version}version>
        dependency>

        <dependency>
            <groupId>org.slf4jgroupId>
            <artifactId>slf4j-apiartifactId>
            <version>${slf4j.version}version>
        dependency>

        <dependency>
            <groupId>org.slf4jgroupId>
            <artifactId>slf4j-log4j12artifactId>
            <version>${slf4j.version}version>
        dependency>
        

        
        <dependency>
            <groupId>mysqlgroupId>
            <artifactId>mysql-connector-javaartifactId>
            <version>${mysql.version}version>
        dependency>

        <dependency>
            <groupId>org.springframework.datagroupId>
            <artifactId>spring-data-jpaartifactId>
            <version>1.9.0.RELEASEversion>
        dependency>

        <dependency>
            <groupId>org.springframeworkgroupId>
            <artifactId>spring-testartifactId>
            <version>4.2.4.RELEASEversion>
        dependency>
        
        
        <dependency>  
            <groupId>javax.elgroupId>  
            <artifactId>javax.el-apiartifactId>  
            <version>2.2.4version>  
        dependency>  
          
        <dependency>  
            <groupId>org.glassfish.webgroupId>  
            <artifactId>javax.elartifactId>  
            <version>2.2.4version>  
        dependency> 
        
    dependencies>

2.1.2编写配置文件整合Spring Data JPA与Spring

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:aop="http://www.springframework.org/schema/aop"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:jdbc="http://www.springframework.org/schema/jdbc" xmlns:tx="http://www.springframework.org/schema/tx"
       xmlns:jpa="http://www.springframework.org/schema/data/jpa" xmlns:task="http://www.springframework.org/schema/task"
       xsi:schemaLocation="
		http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
		http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd
		http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd
		http://www.springframework.org/schema/jdbc http://www.springframework.org/schema/jdbc/spring-jdbc.xsd
		http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx.xsd
		http://www.springframework.org/schema/data/jpa
		http://www.springframework.org/schema/data/jpa/spring-jpa.xsd">

    

    
    <bean id="entityManagerFactoty" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
        <property name="dataSource" ref="dataSource" />
        
        <property name="packagesToScan" value="实体类包路径" />
        
        <property name="persistenceProvider">
            <bean class="org.hibernate.jpa.HibernatePersistenceProvider"/>
        property>

        
        <property name="jpaVendorAdapter">
            <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
                
                <property name="generateDdl" value="false" />
                
                <property name="database" value="MYSQL" />
                
                <property name="databasePlatform" value="org.hibernate.dialect.MySQLDialect" />
                
                <property name="showSql" value="true" />
            bean>
        property>

        
        <property name="jpaDialect" >
            <bean class="org.springframework.orm.jpa.vendor.HibernateJpaDialect" />
        property>

    bean>

    
    <bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource">
        <property name="user" value="用户名">property>
        <property name="password" value="密码">property>
        <property name="jdbcUrl" value="jdbc:mysql://ip：端口/数据库" >property>
        <property name="driverClass" value="com.mysql.jdbc.Driver">property>
    bean>

    
    <jpa:repositories base-package="实体类包名" transaction-manager-ref="transactionManager"
                   entity-manager-factory-ref="entityManagerFactoty" >jpa:repositories>

    
    <bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
        <property name="entityManagerFactory" ref="entityManagerFactoty">property>
    bean>

    
    <tx:advice id="txAdvice" transaction-manager="transactionManager">
        <tx:attributes>
            <tx:method name="save*" propagation="REQUIRED"/>
            <tx:method name="insert*" propagation="REQUIRED"/>
            <tx:method name="update*" propagation="REQUIRED"/>
            <tx:method name="delete*" propagation="REQUIRED"/>
            <tx:method name="get*" read-only="true"/>
            <tx:method name="find*" read-only="true"/>
            <tx:method name="*" propagation="REQUIRED"/>
        tx:attributes>
    tx:advice>

    
    <aop:config>
        <aop:pointcut id="pointcut" expression="execution(* service包名.*.*(..))" />
        <aop:advisor advice-ref="txAdvice" pointcut-ref="pointcut" />
    aop:config>


    

    
    <context:component-scan base-package="包名(包含所有子包和类)" >context:component-scan>
beans>

2.1.5 使用JPA注解配置映射关系

创建对应数据库的实体类
所有注解都是JPA规范提供的注解，导包为javax.persistence

几个注解

@Entity
	//类上注解，声明为实体类
@Table(name = "表名")
	//类上注解，建立实体类和表的映射关系
@Id
	//属性注解，声明此私有属性为主键
@GeneratedValue(strategy=GenerationType.IDENTITY)
	//属性上注解，配置主键自动生成策略，具体值代表的含义见上一篇
@Colum(name = "字段名")
	//属性注解，指定此属性对应表中的字段

3.配置接口

Spring Data JPA是spring提供的一款对于数据访问层（Dao层）的框架，使用Spring Data JPA，只需要按照框架的规范提供dao接口，不需要实现类就可以完成数据库的增删改查、分页查询等方法的定义，极大的简化了我们的开发过程。

创建符合规范的接口：
1.创建一个Dao层接口，并实现JpaRepository和JpaSpecificationExecutor
2.提供相应的泛型

举例

 import java.util.List;

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.JpaSpecificationExecutor;

import cn.itcast.entity.Customer;

/**
 * JpaRepository<实体类类型，主键类型>：用来完成基本CRUD操作
 * JpaSpecificationExecutor<实体类类型>：用于复杂查询（分页等查询操作）
 */
public interface CustomerDao extends JpaRepository<Customer, Long>, JpaSpecificationExecutor<Customer> {
}

4.完成基本操作

初始注入对象

	@Autowired
    private CustomerDao customerDao;

4.1 保存

	//1.创建对象customer;
	//2.执行方法
	customerDao.save(customer);
	//如果执行此方法是对象中存在id属性，即为更新操作会先根据id查询，再更新    
    //如果执行此方法中对象中不存在id属性，即为保存操作

4.2 删除

  customerDao.delete(1l);//传入id

4.3根据id查询

Customer customer = customerDao.findOne(2l);//传入id

JPQL方式查询

接口内定义查询的抽象方法
使用@Query注解配置JPQL语句

	//查询全部
	@Query(value="from Customer")
    public List<Customer> findAllCustomer();

	//条件查询
	//@Query 使用jpql的方式查询。?1代表参数的占位符，其中1对应方法中的参数索引
    @Query(value="from Customer where custName = ?1")
    public Customer findCustomer(String custName);

	//更新
 	@Query(value="update Customer set custName = ?1 where custId = ?2")
    @Modifying//标识为修改查询
    public void updateCustomer(String custName,Long custId);

使用sql语句需要添加nativeQuery=true

	/**
     * nativeQuery : 使用本地sql的方式查询
     */
    @Query(value="select * from cst_customer",nativeQuery=true)
    public void findSql();

方法命名规则查询

接口内使用规范的命名方式命名查询方法既可以完成查询工作，自动生成查询语句
查询方法：
	findBy开头，条件属性使用关键字连接，属性的首字母大写

附录：关键字用法与对应关系示例：

Keword	示例	JPQL
And	findByLastnameAndFirstname	… where x.lastname = ?1 and x.firstname = ?2
Or	findByLastnameOrFirstname	… where x.lastname = ?1 or x.firstname = ?2
Is,Equals	findByFirstnameIs,findByFirstnameEquals	… where x.firstname = ?1
Between	findByStartDateBetween	… where x.startDate between ?1 and ?2
LessThan	findByAgeLessThan	… where x.age < ?1
LessThanEqual	findByAgeLessThanEqual	… where x.age ⇐ ?1
GreaterThan	findByAgeGreaterThan	… where x.age > ?1
GreaterThanEqual	findByAgeGreaterThanEqual	… where x.age >= ?1
After	findByStartDateAfter	… where x.startDate > ?1
Before	findByStartDateBefore	… where x.startDate < ?1
IsNull	findByAgeIsNull	… where x.age is null
IsNotNull,NotNull	findByAge(Is)NotNull	… where x.age not null
Like	findByFirstnameLike	… where x.firstname like ?1
NotLike	findByFirstnameNotLike	… where x.firstname not like ?1
StartingWith	findByFirstnameStartingWith	… where x.firstname like ?1 (parameter bound with appended %)
EndingWith	findByFirstnameEndingWith	… where x.firstname like ?1 (parameter bound with prepended %)
Containing	findByFirstnameContaining	… where x.firstname like ?1 (parameter bound wrapped in %)
OrderBy	findByAgeOrderByLastnameDesc	… where x.age = ?1 order by x.lastname desc
Not	findByLastnameNot	… where x.lastname <> ?1
In	findByAgeIn(Collection ages)	… where x.age not in ?1
NotIn	findByAgeNotIn(Collection age)	… where x.age not in ?1
True	findByActiveTrue()	… where x.active = true
False	findByActiveFalse()	… where x.active = false
IgnoreCase	findByFirstnameIgnoreCase	… where UPPER(x.firstame) = UPPER(?1)