spring-data-jpa -hibernate --specificationExecutor

Specifications动态查询

在查询某个实体的时候，给定的条件是不固定的，这时就需要动态构建相应的查询语句，在Spring Data JPA中可以通过JpaSpecificationExecutor接口查询。相比JPQL,其优势是类型安全,更加的面向对象

import java.util.List;

import org.springframework.data.domain.Page;
import org.springframework.data.domain.Pageable;
import org.springframework.data.domain.Sort;
import org.springframework.data.jpa.domain.Specification;

/**
 *    JpaSpecificationExecutor中定义的方法
 **/
 public interface JpaSpecificationExecutor {
       //根据条件查询一个对象
     T findOne(Specification spec);    
       //根据条件查询集合
     List findAll(Specification spec);
       //根据条件分页查询
     Page findAll(Specification spec, Pageable pageable);
       //排序查询查询
     List findAll(Specification spec, Sort sort);
       //统计查询
     long count(Specification spec);
}

对于JpaSpecificationExecutor，这个接口基本是围绕着Specification接口来定义的。可以简单的理解为，Specification构造的就是查询条件。

 //构造查询条件
    /**
    *    root    ：Root接口，代表查询的根对象，可以通过root获取实体中的属性
    *    query    ：代表一个顶层查询对象，用来自定义查询
    *    cb        ：用来构建查询，此对象里有很多条件方法
    **/
    public Predicate toPredicate(Root root, CriteriaQuery query, CriteriaBuilder cb);

配置文件

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: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"
       xmlns:contxt="http://www.springframework.org/schema/context"
       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="entityManagerFactoryBean" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
        <property name="dataSource" ref="dataSource"/>

        <property name="packagesToScan" value="com.ytfs.entity"/>
        <property name="persistenceProvider">
            <bean class="org.hibernate.jpa.HibernatePersistenceProvider"/>
        property>

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

    

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

    
    <jpa:repositories base-package="com.ytfs.dao" transaction-manager-ref="transactionManager"
                      entity-manager-factory-ref="entityManagerFactoryBean"/>


    

    <context:component-scan base-package="com.ytfs"/>
    
    <context:property-placeholder location="classpath:jdbcConfig.properties"/>
    <bean id="dataSource" class="com.alibaba.druid.pool.DruidDataSource">
        <property name="driverClassName" value="${jdbc.driver}"/>
        <property name="username" value="${jdbc.username}"/>
        <property name="password" value="${jdbc.password}"/>
        <property name="url" value="${jdbc.url}"/>
    bean>
beans>

jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/jpa
jdbc.username=root
jdbc.password=root

 

实体类

　　

package com.ytfs.entity;

import javax.persistence.*;
import java.io.Serializable;

/**
 * @Classname Customer
 * @Description TODO(客户的实体类)
 * @Date 2020/5/6 16:15
 * @Created by ytfs
 */

@Entity
@Table(name = "cst_customer")
public class Customer implements Serializable {
    /**
     * cust_id` bigint(32) NOT NULL AUTO_INCREMENT COMMENT '客户编号(主键)',
     * `cust_name` varchar(32) NOT NULL COMMENT '客户名称(公司名称)',
     * `cust_source` varchar(32) DEFAULT NULL COMMENT '客户信息来源',
     * `cust_industry` varchar(32) DEFAULT NULL COMMENT '客户所属行业',
     * `cust_level` varchar(32) DEFAULT NULL COMMENT '客户级别',
     * `cust_address` varchar(128) DEFAULT NULL COMMENT '客户联系地址',
     * `cust_phone` v
     */
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "cust_id")
    private Long custId;

    @Column(name = "cust_name")
    private String custName;

    @Column(name = "cust_source")
    private String custSource;

    @Column(name = "cust_industry")
    private String custIndustry;

    @Column(name = "cust_level")
    private String custLevel;

    @Column(name = "cust_address")
    private String custAddress;

    @Column(name = "cust_phone")
    private String custPhone;

    public Long getCustId() {
        return custId;
    }

    public void setCustId(Long custId) {
        this.custId = custId;
    }

    public String getCustName() {
        return custName;
    }

    public void setCustName(String custName) {
        this.custName = custName;
    }

    public String getCustSource() {
        return custSource;
    }

    public void setCustSource(String custSource) {
        this.custSource = custSource;
    }

    public String getCustIndustry() {
        return custIndustry;
    }

    public void setCustIndustry(String custIndustry) {
        this.custIndustry = custIndustry;
    }

    public String getCustLevel() {
        return custLevel;
    }

    public void setCustLevel(String custLevel) {
        this.custLevel = custLevel;
    }

    public String getCustAddress() {
        return custAddress;
    }

    public void setCustAddress(String custAddress) {
        this.custAddress = custAddress;
    }

    public String getCustPhone() {
        return custPhone;
    }

    public void setCustPhone(String custPhone) {
        this.custPhone = custPhone;
    }

    @Override
    public String toString() {
        return "Customer{" +
                "custId=" + custId +
                ", custName='" + custName + '\'' +
                ", custSource='" + custSource + '\'' +
                ", custIndustry='" + custIndustry + '\'' +
                ", custLevel='" + custLevel + '\'' +
                ", custAddress='" + custAddress + '\'' +
                ", custPhone='" + custPhone + '\'' +
                '}';
    }
}

 

Dao接口

package com.ytfs.dao;

import com.ytfs.entity.Customer;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.JpaSpecificationExecutor;

/**
 * @Classname ICustomerDao
 * @Description TODO(客户的数据访问层)
 * @Date 2020/5/6 16:20
 * @Created by ytfs
 */


public interface ICustomerDao  extends JpaRepository, JpaSpecificationExecutor {
}

 

查询测试

package com.ytfs.test;

import com.ytfs.dao.ICustomerDao;
import com.ytfs.entity.Customer;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.PageRequest;
import org.springframework.data.domain.Pageable;
import org.springframework.data.domain.Sort;
import org.springframework.data.jpa.domain.Specification;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;

import javax.persistence.criteria.*;
import java.util.ArrayList;
import java.util.List;
import java.util.Optional;

/**
 * @Classname Test
 * @Description TODO(测试)
 * @Date 2020/5/6 16:21
 * @Created by ytfs
 */

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = "classpath:applicationContext.xml")
public class TestSpringDataJPA {

    @Autowired
    private ICustomerDao customerDao;

    /**
     * 根据名称查询用户
     */
    @Test
    public void testFindAll() {
        //匿名内部类
        /**
         * 自定义查询条件
         *      1.实现Specification接口（提供泛型：查询的对象类型）
         *      2.实现toPredicate方法（构造查询条件）
         *      3.需要借助方法参数中的两个参数（
         *          root：获取需要查询的对象属性
         *          CriteriaBuilder：构造查询条件的，内部封装了很多的查询条件（模糊匹配，精准匹配）
         *       ）
         *  案例：根据客户名称查询，查询客户名为传智播客的客户
         *          查询条件
         *              1.查询方式
         *                  criteriaBuilder对象
         *              2.比较的属性名称
         *                  root对象
         *
         */
        Specification spec = new Specification() {
            @Override
            public Predicate toPredicate(Root root, CriteriaQuery criteriaQuery, CriteriaBuilder criteriaBuilder) {
                //1.获取比较的属性
                Path