springDataJpa入门教程（4）-Example单表动态条件查询+分页

springDataJpa入门教程

• springDataJpa入门教程（1）-基于springBoot的基本增删改查

• springDataJpa入门教程（2）-Specification动态条件查询+排序+分页

• springDataJpa入门教程（3-1）-基于EntityManager原生sql多表联合查询+动态条件查询+分页

• springDataJpa入门教程（3-2）-基于EntityManager原生sql多表联合查询+动态条件查询+分页返回自定义实体类对象

• springDataJpa入门教程（4）-Example单表动态条件查询+分页

• springDataJpa入门教程（5）-单表动态条件查询+分页

• springDataJpa入门教程（6）-多表动态条件查询+分页

• springDataJpa入门教程（7）-基于springDataJpa投影(Projection)返回自定义实体类对象

• springDataJpa入门教程（8）-JPA EnableJpaAuditing 审计功能

• springDataJpa入门教程（9）-spring jpa实体属性类型转换器AttributeConverter的用法

• springDataJpa入门教程（10）-JPA使用过程中遇到的坑及解决方法

springDataJpa入门教程（4）-Example单表动态条件查询+分页

这节来讲下怎么使用springDataJpa实现简单的单表动态条件查询+分页，下面以springDataJpa提供的Example来讲解单表动态条件查询+分页。源码地址：源码下载地址。java学习交流群：184998348,欢迎大家一起交流学习。

1. 用到的实体类是User类,下面这个类的代码：

package com.thizgroup.jpa.study.model;

import java.util.Date;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;

@Entity
@Table(name = "tb_user")
@Data//使用lombok生成getter、setter
@NoArgsConstructor//生成无参构造方法
public class User {

  @Id
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  private Long id;

  @Column(name = "name",columnDefinition = "varchar(64)")
  private String name;

  @Column(name = "mobile",columnDefinition = "varchar(64)")
  private String mobile;

  @Column(name = "email",columnDefinition = "varchar(64)")
  private String email;

  @Column(name = "age",columnDefinition = "smallint(64)")
  private Integer age;

  @Column(name = "birthday",columnDefinition = "timestamp")
  private Date birthday;

  //地址
  @Column(name = "address_id",columnDefinition = "bigint(20)")
  private Long addressId;

  @Column(name = "create_date",columnDefinition = "timestamp")
  private Date createDate;

  @Column(name = "modify_date",columnDefinition = "timestamp")
  private Date modifyDate;

  @Builder(toBuilder = true)
  public User(Long id,String name, String mobile, String email, Integer age, Date birthday,
      Long addressId) {
    this.id = id;
    this.name = name;
    this.mobile = mobile;
    this.email = email;
    this.age = age;
    this.birthday = birthday;
    this.addressId = addressId;
  }
}

下面，在IUserService中添加一个查询方法,

package com.thizgroup.jpa.study.service;

import com.thizgroup.jpa.study.model.User;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.Pageable;

/**
 * 用户服务
 */
public interface IUserService {
  /**
   * example单表动态条件分页查询
   */
  Page<User> findUserListByPage(User user,Pageable pageable);
}

然后在UserServiceImpl类中实现这个方法，

package com.thizgroup.jpa.study.service.impl;

import com.thizgroup.jpa.study.dao.UserDao;
import com.thizgroup.jpa.study.dao.UserRepository;
import com.thizgroup.jpa.study.dto.AddressDTO;
import com.thizgroup.jpa.study.dto.PageRecord;
import com.thizgroup.jpa.study.dto.UserDTO;
import com.thizgroup.jpa.study.dto.UserProjection;
import com.thizgroup.jpa.study.model.User;
import com.thizgroup.jpa.study.service.IUserService;
import java.math.BigInteger;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.stream.Collectors;
import javax.persistence.criteria.CriteriaBuilder;
import javax.persistence.criteria.CriteriaQuery;
import javax.persistence.criteria.Order;
import javax.persistence.criteria.Predicate;
import javax.persistence.criteria.Root;
import org.apache.commons.lang3.StringUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.domain.Example;
import org.springframework.data.domain.ExampleMatcher;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.Pageable;
import org.springframework.data.jpa.domain.Specification;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Propagation;
import org.springframework.transaction.annotation.Transactional;
import org.springframework.util.Assert;

@Service
@Transactional(readOnly = false,propagation = Propagation.REQUIRED)
public class UserServiceImpl implements IUserService {

  @Autowired
  private UserRepository userRepository;

   @Override
  public Page<User> findUserListByPage(User user, Pageable pageable) {

    Example<User> example = Example.of(user,
        模糊查询匹配开头，即{name}%
        ExampleMatcher.matching().withMatcher("name",ExampleMatcher.GenericPropertyMatchers.startsWith())
            //是否包含某个字符串 email like ‘%’ + ?0 + ‘%’
        .withMatcher("email",ExampleMatcher.GenericPropertyMatchers.contains())
            //按照年龄精确查询
        .withMatcher("age",ExampleMatcher.GenericPropertyMatchers.exact()));
    return userRepository.findAll(example,pageable);
  }
}

此外，ExampleMatcher.GenericPropertyMatcher还提供了其他的查询条件，整理如下：

方法	描述
ignoreCase	忽略大小写
caseSensitive	大小写敏感
endsWith	以什么结尾
exact	精确查询
contains	是否包含某个字符串
startsWith	以什么开始
regex	使用正则表达式匹配

不幸的是，即使开发人员最初认为支持正则表达式（因为存在上述枚举常量），Spring实际上目前不支持它们——并且根据相关JILA问题的讨论，它永远不会：HTTPS://JIRA.SpRIP.IO/BROSESE/DATAJPA-944

下面写个单元测试验证上面的代码：

package com.thizgroup.jpa.study.service;

import com.thizgroup.jpa.study.JpaApplication;
import com.thizgroup.jpa.study.model.User;
import java.util.ArrayList;
import java.util.List;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.PageRequest;
import org.springframework.test.annotation.Rollback;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import org.springframework.transaction.annotation.Propagation;
import org.springframework.transaction.annotation.Transactional;

@SpringBootTest(classes={JpaApplication.class})
@RunWith(SpringJUnit4ClassRunner.class)
@Transactional(readOnly = false,propagation = Propagation.REQUIRED)
public class UserServiceImplTest {

  @Autowired
  private IUserService userService;
  
  @Test
  public void findUserListByPage3Test() throws Exception{
    User u = new User();
    u.setName("张");
    u.setEmail("@qq.com");
    u.setAge(35);
    //注意：jpa的分页是从0开始的
    Page<User> pageList = userService.findUserListByPage(u, PageRequest.of(0, 15));
    System.out.println("分页信息：");
    System.out.println("总记录数："+pageList.getTotalElements()+",总页数："+pageList.getTotalPages());
    System.out.println("页码："+(pageList.getNumber()+1)+",每页条数："+pageList.getSize());
    List<User> content = pageList.getContent();
    content = null == content? new ArrayList<>() : content;
    content.forEach(user->System.out.println(user));
  }
}

运行上面的单元测试，结果如下：

分页信息：
总记录数：1,总页数：1
页码：1,每页条数：15
User(id=1, name=张三, mobile=156989989, email=hu@qq.com, age=35, birthday=2008-09-16 08:00:00.0, addressId=11, createDate=2019-08-06 05:50:01.0, modifyDate=2019-08-08 05:46:11.0)

如果需要详细了解Example查询，推荐这篇文章：Spring Data JPA 实例查询.

至此，springDataJpa Example单表动态条件查询+分页就介绍完了，有需要源码的朋友，请到git上下载源码，源码地址：https://github.com/hgq0916/springdatajpa-study.git。java学习交流群：184998348,欢迎大家一起交流学习。

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