Spring data JPA(1)

Day 5:

Dependencies

Before the emergence of Spring boot, we need to add these two dependencies if we want to use Spring data jpa.

<dependency>
  <groupId>org.springframework.data</groupId>
  <artifactId>spring-data-jpa</artifactId>
  <version>2.1.8.RELEASE</version>
</dependency>

<dependency>
  <groupId>org.hibernate</groupId>
  <artifactId>hibernate-entitymanager</artifactId>
  <version>5.4.2.Final</version>
</dependency>

If we have Spring boot, we add the following dependency instead.

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>

xml configuration

Without Spring boot, we have to write many configurations in a xml file.

<?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:context="http://www.springframework.org/schema/context"
       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.xsd
		http://www.springframework.org/schema/data/jpa http://www.springframework.org/schema/data/jpa/spring-jpa-1.3.xsd
		http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.0.xsd
		http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd">

    <!--1 配置数据源-->
    <bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
        <property name="driverClassName" value="com.mysql.jdbc.Driver"/>
        <property name="username" value="root"/>
        <property name="password" value="root"/>
        <property name="url" value="jdbc:mysql:///spring_data"/>
    </bean>

    <!--2 配置EntityManagerFactory-->
    <bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
        <property name="dataSource" ref="dataSource"/>
        <property name="jpaVendorAdapter">
            <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter"/>
        </property>
        <property name="packagesToScan" value="com.imooc"/>

        <property name="jpaProperties">
            <props>
                <prop key="hibernate.ejb.naming_strategy">org.hibernate.cfg.ImprovedNamingStrategy</prop>
                <prop key="hibernate.dialect">org.hibernate.dialect.MySQL5InnoDBDialect</prop>
                <prop key="hibernate.show_sql">true</prop>
                <prop key="hibernate.format_sql">true</prop>
                <prop key="hibernate.hbm2ddl.auto">update</prop>
            </props>
        </property>

    </bean>

    <!--3 配置事务管理器-->
    <bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
        <property name="entityManagerFactory" ref="entityManagerFactory"/>
    </bean>

    <!--4 配置支持注解的事务-->
    <tx:annotation-driven transaction-manager="transactionManager"/>

    <!--5 配置spring data-->
    <jpa:repositories base-package="com.imooc" entity-manager-factory-ref="entityManagerFactory"/>

    <context:component-scan base-package="com.imooc"/>

</beans>

Create an entity

@Entity
public class Employee {

    @Id
    @GeneratedValue
    private Integer id;

    @Column(length = 50)
    private String name;

    private Integer age;

    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 Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }
}

Create Repositories

If we use Spring boot, actually we do not need to write any xml. We only need to add a dependency and define our DAO entity class. Now, we can create a repository interface to manipulate our database.

public interface EmployeeRepository extends Repository<Employee, Integer> {
    public Employee findByName(String name);
}

Done! Now we can use this method directly without any implement code!

private EmployeeRepository employeeRepository = null;

public void findByName() {
    Employee aaa = employeeRepository.findByName("aaa");
    System.out.println("aaa = " + aaa.getName());
}

Notice that the name of this method, findByName, must follow some rules.