Spring Data JPA 示例

在这篇文章中，我们将了解 Spring 数据 JPA。 Spring data JPA 提供 jpaTemplate 来集成 Spring 和 JPA。

为什么选择 Spring 数据 JPA：

现在实现数据访问层相当麻烦。您甚至需要编写太多样板代码才能执行简单的查询，并且您必须在执行查询之前和之后编写太多代码。Spring data JPA 提供的 API 非常抽象，您只需要编写存储库接口，Spring data JPA 就会自动提供实现。您还可以声明一些自定义查找方法（findCountryByName），spring 会为其提供实现。

下载源代码：

下载

让我们借助示例了解更多信息： 使用以下代码在 mysql 数据库中创建 Country 表：

CREATE TABLE COUNTRY
(
   id int PRIMARY KEY NOT NULL AUTO_INCREMENT,
   countryName varchar(100) NOT NULL,
   population int NOT NULL
)
;

我们将使用 Country 表来查询和更新数据库中的值。 第 1 步： 创建一个简单的 maven java 项目作为“SpringDataJPAHibernateExample”。 步骤 2： 在 pom.xml 中包含 Spring 数据、hibernate 和 mysql 依赖项。

<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>org.arpit.java2blog</groupId>
<artifactId>SpringDataJPAHibernateExample</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>

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

<properties>
  <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  <spring.version>4.2.1.RELEASE</spring.version>
  <hibernate.version>4.3.5.Final</hibernate.version>

</properties>

<dependencies>
  <dependency>
   <groupId>junit</groupId>
   <artifactId>junit</artifactId>
   <version>3.8.1</version>
   <scope>test</scope>
  </dependency>
  <dependency>
   <groupId>org.springframework</groupId>
   <artifactId>spring-core</artifactId>
   <version>${spring.version}</version>
  </dependency>
  <dependency>
   <groupId>org.springframework</groupId>
   <artifactId>spring-context</artifactId>
   <version>${spring.version}</version>
  </dependency>
  <dependency>
   <groupId>org.springframework.data</groupId>
   <artifactId>spring-data-jpa</artifactId>
   <version>1.8.0.RELEASE</version>
  </dependency>
  <dependency>
   <groupId>org.hibernate.javax.persistence</groupId>
   <artifactId>hibernate-jpa-2.1-api</artifactId>
   <version>1.0.0.Final</version>
  </dependency>
  <dependency>
   <groupId>org.hibernate</groupId>
   <artifactId>hibernate-entitymanager</artifactId>
   <version>${hibernate.version}</version>
   <scope>runtime</scope>
  </dependency>
  <dependency>
   <groupId>mysql</groupId>
   <artifactId>mysql-connector-java</artifactId>
   <version>5.1.6</version>
  </dependency>
  <dependency>
   <groupId>commons-dbcp</groupId>
   <artifactId>commons-dbcp</artifactId>
   <version>1.4</version>
  </dependency>
</dependencies>
</project>

第 3 步：让我们创建我们的 bean 类 Country.java

package org.arpit.java2blog.model;

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

/*
* This is our model class and it corresponds to Country table in database
*/
@Entity
@Table(name="COUNTRY")
public class Country{

@Id
@Column(name="id")
@GeneratedValue(strategy=GenerationType.IDENTITY)
int id;

@Column(name="countryName")
String countryName;

@Column(name="population")
long population;

public Country() {
  super();
}
public Country(int i, String countryName,long population) {
  super();
  this.id = i;
  this.countryName = countryName;
  this.population=population;
}
public int getId() {
  return id;
}
public void setId(int id) {
  this.id = id;
}
public String getCountryName() {
  return countryName;
}
public void setCountryName(String countryName) {
  this.countryName = countryName;
}
public long getPopulation() {
  return population;
}
public void setPopulation(long population) {
  this.population = population;
}

@Override
public String toString() {
  return "Country [id=" + id + ", countryName=" + countryName + ", population=" + population + "]";
}
}

第 4 步： 创建一个名为 CountryRepository.java 的存储库接口您不需要提供它的实现，Spring JPA 会自动提供它。

package org.arpit.java2blog.jpa;

import java.util.List;

import org.arpit.java2blog.model.Country;
import org.springframework.data.jpa.repository.Query;
import org.springframework.data.repository.CrudRepository;

public interface CountryRepository extends CrudRepository<Country,Integer> {
    Country findCountryByCountryName(String name);
    @Query("select country from Country country where country.population >= ?1 and country.population  <= ?2")
    List findCountriesPopulationRange(long from, long to);
}

第 5 步： 创建 applicationcontext.xml 如下

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 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:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/jdbc http://www.springframework.org/schema/jdbc/spring-jdbc.xsd
  http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
  http://www.springframework.org/schema/data/jpa http://www.springframework.org/schema/data/jpa/spring-jpa.xsd
  http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx.xsd
  http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd">
<context:annotation-config/>  
<bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
  <property name="entityManagerFactory" ref="entityManagerFactory" />
</bean>
<jpa:repositories base-package="org.arpit.java2blog.jpa" />

<bean id="entityManagerFactory"
  class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
  <property name="dataSource" ref="dataSource" />
  <property name="packagesToScan" value="org.arpit.java2blog" />
  <property name="jpaVendorAdapter">
   <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
    <property name="generateDdl" value="true" />
   </bean>
  </property>
</bean>

<bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource"
  destroy-method="close">
  <property name="driverClassName" value="com.mysql.jdbc.Driver" />
  <property name="url"
   value="jdbc:mysql://localhost:3306/CountryData" />
  <property name="username" value="root" />
  <property name="password" value="arpit123" />
</bean>
<bean id="mainClass" class="org.arpit.java2blog.main.SpringApplicationMainBean">

</bean>
</beans>

根据您的连接详细信息配置数据源。 entityManagerFactory 将引用 dataSource 和 jpaVendorAdapter。 第 6 步： 创建名为 SpringApplicationMainBean.java 的 Main 类，如下所示

package org.arpit.java2blog.main;

import java.util.List;

import javax.sql.DataSource;

import org.arpit.java2blog.jpa.CountryRepository;
import org.arpit.java2blog.model.Country;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class SpringApplicationMainBean
{
@Autowired
private CountryRepository repository;

public static void main(String[] args) {

  ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
  SpringApplicationMainBean samb= (SpringApplicationMainBean) context.getBean("mainClass");  
  samb.addCountries();

  System.out.println("=====================================");
  // Read
  Country countryRead = samb.getCountry(3);
  System.out.println("Getting country with ID 3::" + countryRead.getCountryName());

  System.out.println("=====================================");
  System.out.println("Getting all Countries");
  // Get All
  Iterable countryList = samb.getAllCountries();
  countryList.forEach(c -> System.out.println(c));

  System.out.println("=====================================");
  System.out.println("Finding countryName Bhutan");
  // find country by name
  Country country =samb.findCountryByName("Bhutan");
  System.out.println(country);

  System.out.println("=====================================");
  System.out.println("Finding All Countries which have population from 2000 to 20000");
  // find countries by population ranges
  List countries=samb.findCountryByPopulationRange(2000,20000);
  System.out.println(countries);

  System.out.println("=====================================");
  System.out.println("We are done with all operations");
}

public void addCountries()
{
   // Add Country object to database
   Country countryUSA = new Country();
   countryUSA.setCountryName("USA");
   countryUSA.setPopulation(10000);

   Country countryIndia = new Country();
   countryIndia.setCountryName("India");
   countryIndia.setPopulation(20000);

   Country countryChina = new Country();
   countryChina.setCountryName("China");
   countryChina.setPopulation(30000);

   Country countryBhutan = new Country();
   countryBhutan.setCountryName("Bhutan");
   countryBhutan.setPopulation(5000);

   // Add Country
   repository.save(countryUSA);
   repository.save(countryIndia);
   repository.save(countryChina);
   repository.save(countryBhutan);
}
public Country getCountry(int id)
{
  return repository.findOne(id);
}
public Iterable getAllCountries()
{
  return repository.findAll();
}

public Country findCountryByName(String countryName)
{
  return repository.findCountryByCountryName(countryName);
}

public List findCountryByPopulationRange(long populationTo,long populationFrom)
{
  return repository.findCountriesPopulationRange(populationTo,populationFrom);
}
}

如您所见，我们在上面的类中使用了 autowire 注解来注入 CountryRepository。Spring 自动提供了一些常用方法的实现，例如 save、delete、findAll 等。

当你运行上面的程序时，你会得到下面的输出：

SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder".
SLF4J: Defaulting to no-operation (NOP) logger implementation
SLF4J: See http://www.slf4j.org/codes.html#StaticLoggerBinder for further details.
Sep 13, 2016 12:36:15 PM org.hibernate.jpa.internal.util.LogHelper logPersistenceUnitInformation
INFO: HHH000204: Processing PersistenceUnitInfo [
name: default
...]
Sep 13, 2016 12:36:16 PM org.hibernate.Version logVersion
INFO: HHH000412: Hibernate Core {4.3.5.Final}
Sep 13, 2016 12:36:16 PM org.hibernate.cfg.Environment
INFO: HHH000206: hibernate.properties not found
Sep 13, 2016 12:36:16 PM org.hibernate.cfg.Environment buildBytecodeProvider
INFO: HHH000021: Bytecode provider name : javassist
Sep 13, 2016 12:36:16 PM org.hibernate.annotations.common.reflection.java.JavaReflectionManager
INFO: HCANN000001: Hibernate Commons Annotations {4.0.4.Final}
Sep 13, 2016 12:36:17 PM org.hibernate.dialect.Dialect
INFO: HHH000400: Using dialect: org.hibernate.dialect.MySQL5Dialect
Sep 13, 2016 12:36:17 PM org.hibernate.engine.jdbc.internal.LobCreatorBuilder useContextualLobCreation
INFO: HHH000423: Disabling contextual LOB creation as JDBC driver reported JDBC version [3] less than 4
Sep 13, 2016 12:36:17 PM org.hibernate.hql.internal.ast.ASTQueryTranslatorFactory
INFO: HHH000397: Using ASTQueryTranslatorFactory
Sep 13, 2016 12:36:18 PM org.hibernate.tool.hbm2ddl.SchemaUpdate execute
INFO: HHH000228: Running hbm2ddl schema update
Sep 13, 2016 12:36:18 PM org.hibernate.tool.hbm2ddl.SchemaUpdate execute
INFO: HHH000102: Fetching database metadata
Sep 13, 2016 12:36:18 PM org.hibernate.tool.hbm2ddl.SchemaUpdate execute
INFO: HHH000396: Updating schema
Sep 13, 2016 12:36:18 PM org.hibernate.tool.hbm2ddl.TableMetadata
INFO: HHH000261: Table found: CountryData.country
Sep 13, 2016 12:36:18 PM org.hibernate.tool.hbm2ddl.TableMetadata
INFO: HHH000037: Columns: [countryname, id, population]
Sep 13, 2016 12:36:18 PM org.hibernate.tool.hbm2ddl.TableMetadata
INFO: HHH000108: Foreign keys: []
Sep 13, 2016 12:36:18 PM org.hibernate.tool.hbm2ddl.TableMetadata
INFO: HHH000126: Indexes: [primary]
Sep 13, 2016 12:36:18 PM org.hibernate.tool.hbm2ddl.SchemaUpdate execute
INFO: HHH000232: Schema update complete
=====================================
Getting country with ID 3::China
=====================================
Getting all Countries
Country [id=1, countryName=USA, population=10000]
Country [id=2, countryName=India, population=20000]
Country [id=3, countryName=China, population=30000]
Country [id=4, countryName=Bhutan, population=5000]
=====================================
Finding countryName Bhutan
Country [id=4, countryName=Bhutan, population=5000]
=====================================
Finding All Countries which have population from 2000 to 20000
[Country [id=1, countryName=USA, population=10000], Country [id=2, countryName=India, population=20000], Country [id=4, countryName=Bhutan, population=5000]]
=====================================
We are done with all operations

原文链接：https://codingdict.com/

Spring Data JPA 示例

为什么选择 Spring 数据 JPA：

下载源代码：

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