1. Spring Data JPA是什么

它是Spring基于ORM框架、JPA规范封装的一套JPA应用框架,可使开发者用极简的代码即可实现对数据的访问和操作。它提供了包括增删改查等在内的常用功能,且易于扩展。学习并使用Spring Data JPA可以极大提高开发效率。

2. Spring Data JPA 有什么

主要看看Spring Data JPA 提供的编程接口

  • Repository:最顶层的接口,是一个空接口,目的是为了统一所有的Repository的类型,且能让组件扫描时自动识别。
  • CrudRepository: Repository的子接口,提供CRUD的功能。
  • PagingAndSortingRepository: CrudRepository的子接口, 添加分页排序。
  • JpaRepository: PagingAndSortingRepository的子接口,增加批量操作等。
  • JpaSpecificationExecutor: 用来做复杂查询的接口。

接口继承关系图

    

3. 利用Spring Data JPA建立简单的用户管理项目

3.1 搭建项目

3.1.1 数据库建表

    

3.1.2 用户管理工程包结构

  • com.zang.usermanage.repository (存放自定义的数据操作接口)
  • com.zang.usermanage.model(存放实体模型)
  • com.zang.usermanage.service(存放服务层的接口和实现)
  • com.zang.usermanage.controller (如果是MVC项目可建立此包,存放控制器)
  • com.zang.usermanage.exception(存放异常类)
  • com.zang.usermanage.test(存放测试类)

    

3.1.3 所有需要的jar包

  • Spring 基础jar包(版本:4.1.5)
  • Spring Data Commons jar包(版本:1.9.2)
  • Spring Data JPA jar包(版本:1.7.2)
  • Hibernate 相关 jar包(版本:4.2.0)
  • MySQL数据库连接包 (版本:5.1.21)
  • 日志相关jar包
  • 其它jar包

3.1.4 配置与编码

创建配置

配置文件一:applicationContext.xml(Spring上下文)

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<beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"  
    xmlns:context="http://www.springframework.org/schema/context"   
    xmlns:jdbc="http://www.springframework.org/schema/jdbc"    
    xmlns:jee="http://www.springframework.org/schema/jee"   
    xmlns:tx="http://www.springframework.org/schema/tx"  
    xmlns:jpa="http://www.springframework.org/schema/data/jpa"  
    xsi:schemaLocation="  
        http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.2.xsd  
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.2.xsd  
        http://www.springframework.org/schema/jdbc http://www.springframework.org/schema/jdbc/spring-jdbc-3.2.xsd  
        http://www.springframework.org/schema/jee http://www.springframework.org/schema/jee/spring-jee-3.2.xsd  
        http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.2.xsd  
        http://www.springframework.org/schema/data/jpa http://www.springframework.org/schema/data/jpa/spring-jpa.xsd"  
    default-lazy-init="true">

    <!--第一步-->
    <!--定义服务层代码存放的包扫描路径-->
    <context:component-scan base-package="com.zang.usermanage.service" />

    <!--第二步-->
    <!--定义实体的工厂bean-->
    <bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
        <property name="persistenceUnitName" value="userPU" />
        <property name="persistenceXmlLocation" value="classpath:persistence.xml"></property>
    </bean>

    <!--第三步-->
    <!--定义事务管理器-->
    <bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
        <property name="entityManagerFactory" ref="entityManagerFactory"/>
    </bean>

    <!--第四步-->
    <!--定义repository接口的存放目录-->
    <!--定义接口实现的后缀,通常用Impl-->
    <!--定义实体工厂的引用-->
    <!--定义事务管理器的引用-->
       <jpa:repositories base-package="com.zang.usermanage.repository"
                         repository-impl-postfix="Impl" 
                         entity-manager-factory-ref="entityManagerFactory" 
                         transaction-manager-ref="transactionManager"/>


    <!--第五步-->
    <!--声明采用注解的方式申明事务-->
    <tx:annotation-driven transaction-manager="transactionManager"/>

</beans>
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配置文件二:persistence.xml(管理持久化)

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<?xml version="1.0" encoding="UTF-8"?>
<persistence xmlns="http://java.sun.com/xml/ns/persistence" version="2.0">
    <persistence-unit name="userPU" transaction-type="RESOURCE_LOCAL">
        <!--jpa的提供者-->
        <provider>org.hibernate.ejb.HibernatePersistence</provider>
        <properties>
            <!--声明数据库连接的驱动-->
            <property name="hibernate.connection.driver_class" value="com.mysql.jdbc.Driver"/>
            <!--jdbc数据库的连接地址-->
            <property name="hibernate.connection.url" value="jdbc:mysql://localhost:3306/user_manage"/>
            <property name="hibernate.connection.username" value="root"/>
            <property name="hibernate.connection.password" value="123"/>
            <!--配置方言-->
            <property name="hibernate.dialect" value="org.hibernate.dialect.MySQL5Dialect"/>
            <!--激活查询日志功能-->
            <property name="hibernate.show_sql" value="true"/>
            <!--优雅地输出Sql-->
            <property name="hibernate.format_sql" value="true"/>
            <!--添加一条解释型标注-->
            <property name="hibernate.use_sql_comments" value="false"/>
            <!--配置如何根据java模型生成数据库表结构,常用update,validate-->
            <property name="hibernate.hbm2ddl.auto" value="update"/>
        </properties>
    </persistence-unit>
</persistence>
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创建类文件并编码

User.java(用户实体类),UserRepository.java(用户的数据接口,继承JpaRepository接口), UserService.java(用户服务接口),UserServiceImpl.java(接口实现), UserNotFound.java(异常类,在查询实体未找到时抛出)

 类之间关系

     

User.java(用户实体类)

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package com.zang.usermanage.model;

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

/*
实体中常用的注解:
@Entity :声明这个类是一个实体类
@Table:指定映射到数据库的表格
@Id :映射到数据库表的主键属性,一个实体只能有一个属性被映射为主键
@GeneratedValue:主键的生成策略
*/
@Entity
@Table(name="user")
public class User {

    @Id
    @GeneratedValue
    private Integer id;
    private String name;
    private String address;
    private String phone;
    
    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;
    }
    public String getAddress() {
        return address;
    }
    public void setAddress(String address) {
        this.address = address;
    }
    public String getPhone() {
        return phone;
    }
    public void setPhone(String phone) {
        this.phone = phone;
    }
    
}
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UserRepository.java(用户的数据接口) 

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package com.zang.usermanage.repository;
import org.springframework.data.jpa.repository.JpaRepository;
import com.zang.usermanage.model.User;

public interface UserRepository extends JpaRepository<User,Integer> {

}
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3.2 实现简单的增、删、改、查

JpaRepository接口方法:

  • delete删除或批量删除
  • findAll查找所有
  • findOne查找单个
  • save保存单个或批量保存
  • saveAndFlush保存并刷新到数据库

接口源码如下:(实现类为org.springframework.data.jpa.repository.support.SimpleJpaRepository.class)

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package org.springframework.data.jpa.repository;

import java.io.Serializable;
import java.util.List;
import org.springframework.data.domain.Sort;
import org.springframework.data.repository.NoRepositoryBean;
import org.springframework.data.repository.PagingAndSortingRepository;

@NoRepositoryBean
public abstract interface JpaRepository<T, ID extends Serializable>
  extends PagingAndSortingRepository<T, ID>
{
  public abstract List<T> findAll();
  
  public abstract List<T> findAll(Sort paramSort);
  
  public abstract List<T> findAll(Iterable<ID> paramIterable);
  
  public abstract <S extends T> List<S> save(Iterable<S> paramIterable);
  
  public abstract void flush();
  
  public abstract <S extends T> S saveAndFlush(S paramS);
  
  public abstract void deleteInBatch(Iterable<T> paramIterable);
  
  public abstract void deleteAllInBatch();
  
  public abstract T getOne(ID paramID);
}
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3.2.1 编码实现

UserService.java(用户服务接口)

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package com.zang.usermanage.service;

import java.util.List;import com.zang.usermanage.exception.UserNotFound;
import com.zang.usermanage.model.User;

public interface UserService {
    //添加用户
    public void addUser(User user);
    //修改用户
    public User updateUser(User user) throws UserNotFound;
    //删除用户,根据用户编号删除
    public User deleteUser(int id) throws UserNotFound;
    //查询单个用户
    public User getUser(int id);
    //查询所有用户
    public List<User> getUsers(); 
}
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UserServiceImpl.java(接口实现)

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package com.zang.usermanage.service;


import java.util.ArrayList;
import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;import org.springframework.stereotype.Service;

import com.zang.usermanage.exception.UserNotFound;
import com.zang.usermanage.model.User;
import com.zang.usermanage.repository.UserRepository;


@Service("userService")
public class UserServiceImpl implements UserService {
    
    //自动装配
    @Autowired
    private UserRepository userRepository;

    //增加用户调用save方法
    @Override
    public void addUser(User user) {
        userRepository.save(user);
    }

    //更新用户先进行非空判断,再对新用户各个属性进行非空判断并赋值,最后调用save方法
    //自定义异常类 UserNotFound
    @Override
    public User updateUser(User user) throws UserNotFound {  
        User userUpdate = userRepository.findOne(user.getId());
        if (userUpdate==null)
            throw new UserNotFound();
        if (user.getName()!=null)
            userUpdate.setName(user.getName());
        if (user.getAddress()!=null)
            userUpdate.setAddress(user.getAddress());
        if (user.getPhone()!=null)
            userUpdate.setPhone(user.getPhone());
        userRepository.save(userUpdate);
        return userUpdate;
    }

    //删除用户先进行非空判断,最后调用delete方法
    @Override
    public User deleteUser(int id) throws UserNotFound {
        User userDelete = userRepository.findOne(id);
        if (userDelete==null)
            throw new UserNotFound();
        userRepository.delete(userDelete);
        return userDelete;
    }

    //查询单个,调用findOne方法
    @Override
    public User getUser(int id) {

        return userRepository.findOne(id);
    }

    //查询所有,调用findAll方法
    @Override
    public List<User> getUsers() {

        return userRepository.findAll();
    }

}
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3.2.2 测试

Client.java(测试类)

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package com.zang.usermanage.test;

import java.util.List;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.data.domain.Page;

import com.zang.usermanage.exception.UserNotFound;
import com.zang.usermanage.model.User;
import com.zang.usermanage.service.UserService;


public class Client {
    
    public static void printUser(User user){
        StringBuilder sb = new StringBuilder();
        sb.append("id="+user.getId());
        sb.append("name="+user.getName());
        sb.append("address="+user.getAddress());
        sb.append("phone="+user.getPhone());
        System.out.println(sb.toString());
    }
    
    public static void testList(UserService userService){
        List<User> users = userService.getUsers();
        if (users!=null){
            for (int i=0; i<users.size();i++){
                printUser(users.get(i)); 
            }
        }
    }
    public static void testUpate(UserService userService) throws UserNotFound{
        User user = new User();
        user.setId(1);
        user.setAddress("北京路121号");
        userService.updateUser(user);
        testList(userService);   
    }
    
    public static void testAdd(UserService userService){
        User user = new User();
        user.setAddress("天河路120号");
        user.setName("小徐");
        user.setPhone("130000000");
        userService.addUser(user);
        testList(userService);
    }    
    
    public static void testDelete(UserService userService) throws UserNotFound{
        userService.deleteUser(7);
        testList(userService);
    }
    
    public static void main(String[] arg) throws UserNotFound{

        ApplicationContext ac = new ClassPathXmlApplicationContext("applicationContext.xml");
        UserService userService = (UserService) ac.getBean("userService");
        //testList(userService);
        testUpate(userService);
        //testAdd(userService);
        //testDelete(userService);
    }
}
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3.3 实现复杂查询

 3.3.1 基于方法名解析的概念

JpaRepository支持接口规范方法名查询。意思是如果在接口中定义的查询方法符合它的命名规则,就可以不用写实现

例如:findByName这个方法表示从数据库中查询Name这个属性等于XXX的所有记录,类似于SQL语句:select * from xxTable where name=xxx这种形式

这段话有两个重点:

  • 方法名需要在接口中设定
  • 必须符合一定的命名规范

3.3.2 方法名构造方法

find+全局修饰+By+实体的属性名称+限定词+连接词+ ...(其它实体属性)+OrderBy+排序属性+排序方向 例如:findDistinctByFirstNameIgnoreCaseAndLastNameOrderByAgeDesc(String firstName,String lastName){......}

其中:Distinct是全局修饰(非必须),FirstName和LastName是实体的属性名,And是连接词,IgnoreCase是限定词,Age是排序属性,Desc是排序方向,限定词和连接词统称为“关键词”。

3.3.3 目前支持的关键词

常用词如下:

  • 全局修饰:Distinct,Top,First
  • 关键词:IsNull,IsNotNull,Like,NotLike,Containing,In,NotIn,IgnoreCase,Between,Equals,LessThan,GreaterThan,After,Before...
  • 排序方向:Asc,Desc
  • 连接词:And,Or

更多关键词请查看官方在线文档: https://docs.spring.io/spring-data/jpa/docs/2.0.4.RELEASE/reference/html/

3.3.4 嵌套实体方法命名规则

构词法:主实体中子实体的名称+ _ +子实体的属性名称

例如:List<Person> findByAddress_ZipCode(ZipCode zipCode) 表示查询所有 Address(地址)的zipCode(邮编)为指定值的所有Person(人员)

3.3.5 代码展示条件查询、分页、排序

 UserRepository接口定义查询方法

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package com.zang.usermanage.repository;

import java.util.List;

import org.springframework.data.domain.Sort;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.Pageable;
import org.springframework.data.jpa.repository.JpaRepository;

import com.zang.usermanage.model.User;

public interface UserRepository extends JpaRepository<User,Integer> {
        
    //查询需求: 从数据库中查询电话号码(phone)以指定字符串开始(例如:136)的,并且地址(address)中包含指定字符串(例如:路)的记录   提取前两条,降序排列
    //select * from user where phone like '136%' and address like '%路%' order by phone desc limit 0,2
    List<User> findTop2ByPhoneStartingWithAndAddressContainingOrderByPhoneDesc(String phone,String address);
    List<User> findTop2ByPhoneStartingWithAndAddressContaining(String phone,String address,Sort sort);
    
    //分页要用到Pageable接口
    Page<User> findByPhoneStartingWithAndAddressContaining(String phone,String address,Pageable pageable);
    
}
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UserService.java

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package com.zang.usermanage.service;

import java.util.List;

import org.springframework.data.domain.Page;

import com.zang.usermanage.exception.UserNotFound;
import com.zang.usermanage.model.User;

public interface UserService {
        
    //不分页带条件查询
    public List<User> getUsersByConditionNoPage(String phone,String address);
    
    //带分页条件查询(需要得到用户列表并且得到分页信息)
    public Page<User> getUsersByConditionWithPage(String phone,String address,Integer page,Integer pageSize);
    //带分页条件查询(得到用户列表)
    //public List<User> getUsersByCondition(String phone,String address,Integer page,Integer pageSize);
}
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UserServiceImpl.java

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package com.zang.usermanage.service;


import java.util.ArrayList;
import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.PageRequest;
import org.springframework.data.domain.Sort;
import org.springframework.data.domain.Sort.Direction;
import org.springframework.data.domain.Sort.Order;
import org.springframework.stereotype.Service;

import com.zang.usermanage.exception.UserNotFound;
import com.zang.usermanage.model.User;
import com.zang.usermanage.repository.UserRepository;


@Service("userService")
public class UserServiceImpl implements UserService {
    
    //自动装配
    @Autowired
    private UserRepository userRepository;

    @Override
    public Page<User> getUsersByConditionWithPage(String phone,String address,Integer page,Integer pageSize) {
        
        
        //不排序
        Page<User> userPage = userRepository.findByPhoneStartingWithAndAddressContaining(phone,address,new PageRequest(page, pageSize));
        
        //排序(三种方法)
        
        //第一种排序方式
        //Page<User> userPage = userRepository.findByPhoneStartingWithAndAddressContaining(phone,address,new PageRequest(page, pageSize,new Sort(Direction.ASC,"name","phone")));

        //第二种排序方式
        //Order order = new Order(Direction.ASC,"phone");
        //Page<User> userPage = userRepository.findByPhoneStartingWithAndAddressContaining(phone,address,new PageRequest(page, pageSize,new Sort(order));        

        //第三种排序方式
        //List<Order> orders = new ArrayList<Order>();
        //orders.add(new Order(Direction.DESC,"name"));
        //orders.add(new Order(Direction.ASC,"phone"));
        //Page<User> userPage = userRepository.findByPhoneStartingWithAndAddressContaining(phone,address,new PageRequest(page, pageSize,new Sort(orders));

        return userPage;
        
    }

    /**
     * 不分页
     */
    @Override
    public List<User> getUsersByConditionNoPage(String phone,String address) {
        
        return userRepository.findTop2ByPhoneStartingWithAndAddressContainingOrderByPhoneDesc(phone, address);

        //return userRepository.findTop2ByPhoneStartingWithAndAddressContaining(phone, address, new Sort(Direction.ASC,"phone"));

        //Order order = new Order(Direction.ASC,"phone");
        //return userRepository.findTop2ByPhoneStartingWithAndAddressContaining(phone, address, new Sort(order));

        //List<Order> orders = new ArrayList<Order>();
        //orders.add(new Order(Direction.DESC,"name"));
        //orders.add(new Order(Direction.ASC,"phone"));        
        //return userRepository.findTop2ByPhoneStartingWithAndAddressContaining(phone, address, new Sort(orders);
        
    }


}
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Client.java(测试类)

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package com.zang.usermanage.test;

import java.util.List;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.data.domain.Page;

import com.zang.usermanage.exception.UserNotFound;
import com.zang.usermanage.model.User;
import com.zang.usermanage.service.UserService;


public class Client {
    
    public static void printUser(User user){
        StringBuilder sb = new StringBuilder();
        sb.append("id="+user.getId());
        sb.append("name="+user.getName());
        sb.append("address="+user.getAddress());
        sb.append("phone="+user.getPhone());
        System.out.println(sb.toString());
        
    }
    
    /**
     * 打印分页信息
     * @param pageInfo
     */
    public static <T> void printPageInfo(Page<T> pageInfo){
        StringBuilder sb = new StringBuilder();
        sb.append("当前是第几页="+pageInfo.getNumber()).append("\n");
        sb.append("当前页查得的记录数="+pageInfo.getNumberOfElements()).append("\n");
        sb.append("每页需要查询的条数="+pageInfo.getSize()).append("\n");
        sb.append("总共符合条件的记录数="+pageInfo.getTotalElements()).append("\n");
        sb.append("总共的页数是="+pageInfo.getTotalPages()).append("\n");
        System.out.println(sb.toString());
    }
    
    /**
     * 不分页查询
     * @param userService
     */
    public static void testListByConditonNoPage(UserService userService){
        
        List<User> users = userService.getUsersByConditionNoPage("136","路");
        
        if (users!=null){
            for (int i=0; i<users.size();i++){
                printUser(users.get(i));  
            }            
        }
    }    
    
    /**
     * 分页查询
     * @param userService
     */
    public static void testListByConditonWithPage(UserService userService){
        
        //传入条件和分页信息
        Page<User> userPage = userService.getUsersByConditionWithPage("136","路",0,2);
        //打印分页信息
        printPageInfo(userPage);
        
        List<User> users = userPage.getContent();
        
        if (users!=null){
            for (int i=0; i<users.size();i++){
                printUser(users.get(i));            
            }        
        } 
    }
    

    public static void main(String[] arg) throws UserNotFound{

        ApplicationContext ac = new ClassPathXmlApplicationContext("applicationContext.xml");
        UserService userService = (UserService) ac.getBean("userService");

        //testListByConditonNoPage(userService);
        testListByConditonWithPage(userService);        
    }
}
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效果:

 

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