Spring Data

Spring Data’s mission is to provide a familiar and consistent, Spring-based programming model for data access while still retaining the special traits of the underlying data store.

常用子項目

Spring Data JDBC
Spring Data JPA
Spring Data MongoDB
Spring Data Redis

傳統 JDBC

JdbcUtil 工具類

import java.sql.*;

public class JdbcUtil {

    public static Connection getConnection() throws Exception {
        String url = "jdbc:mysql://localhost/db_springboot?useSSL=false";
        String user = "root";
        String password = "123456";
        String driverClass = "com.mysql.jdbc.Driver";
        Class.forName(driverClass);
        return DriverManager.getConnection(url, user, password);
    }

    public static void release(ResultSet resultSet, Statement statement,Connection connection) {
        if (resultSet != null) {
            try {
                resultSet.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }

        if (statement != null) {
            try {
                statement.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }

        if (connection != null) {
            try {
                connection.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}

DAO 接口與實現

import java.util.List;

public interface UserDAO {
    List<User> query();
}

import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.List;

public class UserDAOImpl implements UserDAO {

    @Override
    public List<User> query() {
        List<User> users = new ArrayList<>();

        Connection connection = null;
        PreparedStatement statement = null;
        ResultSet resultSet = null;
        String sql = "select * from user";

        try {
            connection = JdbcUtil.getConnection();
            statement = connection.prepareStatement(sql);
            resultSet = statement.executeQuery();

            User user = null;
            while (resultSet.next()) {
                int id = resultSet.getInt("id");
                String name = resultSet.getString("name");
                int age = resultSet.getInt("age");

                user = new User();
                user.setId(id);
                user.setName(name);
                user.setAge(age);
                users.add(user);
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            JdbcUtil.release(resultSet, statement, connection);
        }

        return users;
    }
}

Test

import org.junit.Assert;
import org.junit.Test;

public class JdbcUtilTest {
    @Test
    public void getConnection() throws Exception {
        Assert.assertNotNull(JdbcUtil.getConnection());
    }
}

Spring JDBC

application.yml 配置 DataSource

spring:
  datasource:
    url: jdbc:mysql://localhost/db_springboot?useSSL=false
    username: root
    password: 123456
    driver-class-name: com.mysql.jdbc.Driver

DAO 層注入 JdbcTemplate

import org.springframework.jdbc.core.JdbcTemplate;

import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.List;

@Repository
public class UserDAOImpl implements UserDAO {

    private final JdbcTemplate jdbcTemplate;

    public UserDAOImpl(JdbcTemplate jdbcTemplate) {
        this.jdbcTemplate = jdbcTemplate;
    }

    @Override
    public List<User> query() {
        final List<User> users = new ArrayList<>();

        String sql = "select * from user";
        jdbcTemplate.query(sql, (ResultSet rs) -> {
            int id = rs.getInt("id");
            String name = rs.getString("name");
            int age = rs.getInt("age");
            User user = new User();
            user.setId(id);
            user.setName(name);
            user.setAge(age);
            users.add(user);
        });

        return users;
    }
}

測試類

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.test.context.junit4.SpringJUnit4ClassRunner;

@RunWith(SpringJUnit4ClassRunner.class)
@SpringBootTest
public class UserDAOImplTest {

    @Autowired
    private UserDAO userDAO;

    @Test
    public void query() {
        List<User> users = userDAO.query();
        users.forEach(System.out::println);
    }
}

Spring Data JPA

User 使用註解可以自動創建表

import lombok.Getter;
import lombok.Setter;
import lombok.ToString;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.validation.constraints.NotEmpty;
import javax.validation.constraints.NotNull;

@Getter
@Setter
@ToString
@Entity
public class User {

    @Id
    @GeneratedValue
    private Integer id;

    @Column(length = 10)
    @NotEmpty
    private String name;

    @NotNull
    private Integer age;
}

UserRepository

import org.springframework.data.repository.Repository;

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

Test

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.test.context.junit4.SpringJUnit4ClassRunner;

@RunWith(SpringJUnit4ClassRunner.class)
@SpringBootTest
public class UserRepositoryTest {

    @Autowired
    private UserRepository userRepository;

    @Test
    public void findByName() {
        System.out.println(userRepository.getfindName("LeifChen"));
    }
}

Reposiroty 接口

public interface Repository<T, ID> {}

Reposiroty 接口是 Spring Data 的核心接口，不提供任何實現方法。是一個空接口，也稱爲標記接口。

(1) CrudRepository：繼承 Repository，實現了 CRUD 相關方法。

<S extends T> S save(S entity); 保存實體
<S extends T> Iterable<S> saveAll(Iterable<S> entities); 保存實體集合
Optional<T> findById(ID id); 根據 id 查詢實體
boolean existsById(ID id); 返回是否存在對應 id 的實體
Iterable<T> findAll(); 返回所有實體
Iterable<T> findAllById(Iterable<ID> ids); 根據 ids 查詢實體
long count(); 返回實體數
void deleteById(ID id); 根據 id 刪除實體
void delete(T entity); 根據實體刪除
void deleteAll(Iterable<? extends T> entities); 根據實體列表刪除
void deleteAll(); 刪除所有實體

(2) PagingAndSortingRepository：繼承 CurdRepository，實現了分頁排序相關方法

Iterable<T> findAll(Sort sort); 查詢所有實體並按照 sort 排序
Page<T> findAll(Pageable pageable); 分頁查詢

測試代碼：

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.data.domain.Pageable;
import org.springframework.data.domain.Sort;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;

@RunWith(SpringJUnit4ClassRunner.class)
@SpringBootTest
public class UserRepositoryTest {

    @Autowired
    private UserRepository userRepository;

    @Test
    public void pageAndSort() {
        Pageable pageable = PageRequest.of(0, 5, Sort.Direction.DESC, "age");
        Page<User> page = userRepository.findAll(pageable);

        System.out.println("查詢的總頁數：" + page.getTotalPages());
        System.out.println("查詢的總記錄數：" + page.getTotalElements());
        System.out.println("查詢的當前第幾頁：" + (page.getNumber() + 1));
        System.out.println("查詢的當前頁面的集合：" + page.getContent());
        System.out.println("查詢的當前頁面的記錄數：" + page.getNumberOfElements());
    }
}

(3) JpaRepository：繼承 PagingAndSortingRepository，實現了 JPA 規範相關方法

測試代碼：

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.test.context.junit4.SpringJUnit4ClassRunner;

@RunWith(SpringJUnit4ClassRunner.class)
@SpringBootTest
public class UserRepositoryTest {

    @Autowired
    private UserRepository userRepository;

    @Test
    public void find() {
        userRepository.findById(3).ifPresent(System.out::println);
    }

    @Test
    public void exist() {
        System.out.println("user(3)：" + userRepository.existsById(3));
        System.out.println("user(100)：" + userRepository.existsById(100));
    }
}

(4) JpaSpecificationExecutor：用來實現 JPA 的動態複雜條件查詢

測試代碼：

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.data.domain.Pageable;
import org.springframework.data.domain.Sort;
import org.springframework.data.jpa.domain.Specification;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;

import javax.persistence.criteria.Path;

@RunWith(SpringJUnit4ClassRunner.class)
@SpringBootTest
public class UserRepositoryTest {

    @Autowired
    private UserRepository userRepository;

    @SuppressWarnings("unchecked")
    @Test
    public void complexQuery() {
        Pageable pageable = PageRequest.of(0, 5, Sort.Direction.ASC, "age");
        Specification<User> specification = (Specification<User>) (root, query, criteriaBuilder) -> {
            Path path = root.get("age");
            return criteriaBuilder.gt(path, 30);
        };
        Page<User> page = userRepository.findAll(specification, pageable);

        System.out.println("查詢的總頁數：" + page.getTotalPages());
        System.out.println("查詢的總記錄數：" + page.getTotalElements());
        System.out.println("查詢的當前第幾頁：" + (page.getNumber() + 1));
        System.out.println("查詢的當前頁面的集合：" + page.getContent());
        System.out.println("查詢的當前頁面的記錄數：" + page.getNumberOfElements());
    }
}

自定義 Reposiroty 接口的兩種方法：

(1) 繼承 Reposiroty 接口

import com.chen.model.User;
import org.springframework.data.repository.Repository;

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

(2) 註解 @RepositoryDefinition

import org.springframework.data.repository.RepositoryDefinition;

@RepositoryDefinition(domainClass = User.class, idClass = Integer.class)
public interface UserRepository {
    User findByName(String name);
}

JPA 方法關鍵字定義規則

參考官方文檔

Keyword	Sample	JPQL snippet
And	findByNameAndAge	… where x.name = ?1 and x.age = ?2
Or	findByNameOrAge	… where x.name = ?1 or x.age = ?2
Is,Equals	findByName,findByNameIs,findByNameEquals	… where x.name = ?1
Between	findByStartDateBetween	… where x.startDate between ?1 and ?2
LessThan	findByAgeLessThan	… where x.age < ?1
LessThanEqual	findByAgeLessThanEqual	… where x.age <= ?1
GreaterThan	findByAgeGreaterThan	… where x.age > ?1
GreaterThanEqual	findByAgeGreaterThanEqual	… where x.age >= ?1
After	findByStartDateAfter	… where x.startDate > ?1
Before	findByStartDateBefore	… where x.startDate < ?1
IsNull	findByAgeIsNull	… where x.age is null
IsNotNull,NotNull	findByAge(Is)NotNull	… where x.age is not null
Like	findByNameLike	… where x.name like ?1
NotLike	findByNameNotLike	… where x.name not like ?1
StartingWith	findByNameStartingWith	… where x.name like ?1 (parameter bound with appended %)
EndingWith	findByNameEndingWith	… where x.name like ?1 (parameter bound with prepended %)
Containing	findByNameContaining	… where x.name like ?1 (parameter bound wrapped in %)
OrderBy	findByNameOrderByAgeDesc	… where x.name = ?1 order by x.age desc
Not	findByNameNot	… where x.lastname <> ?1
In	findByAgeIn(`Collection<Age> ages`)	… where x.age in ?1
NotIn	findByAgeNotIn(`Collection<Age> ages`)	… where x.age not in ?1
True	findByActiveTrue()	… where x.active = true
False	findByActiveFalse()	… where x.active = false
IgnoreCase	findByNameIgnoreCase	… where UPPER(x.name) = UPPER(?1)

其中 find 關鍵字也可以爲 get (例如：getByName) ，使用關鍵字命名方法會導致名稱特別長，並且很難實現複雜查詢，因此還可以通過註解的方式擴展。

註解

@Query：查詢
@Modifying：更新、刪除
@Transactional：事務，一般在 Service 層

參考代碼：

UserRepository

import org.springframework.data.jpa.repository.Modifying;
import org.springframework.data.jpa.repository.Query;
import org.springframework.data.repository.Repository;
import org.springframework.data.repository.query.Param;

import java.util.List;

public interface UserRepository extends Repository<User, Integer> {

    /**
     * 根據名稱查詢用戶（使用 JPA 命名規則）
     *
     * @param name 名稱
     * @return
     */
    User findByName(String name);

    /** 
    * 查詢 id 爲最大值的用戶 
    * 
    * @return 
    */
    @Query("select u from #{#entityName} u where id=(select max(id) from User t1)")
    User findByMaxId();

    /**
     * 根據名稱、年齡查詢用戶（使用 @Query 註解及佔位符 ? 綁定參數）
     *
     * @param name 名稱
     * @param age  年齡
     * @return
     */
    @Query("select u from #{#entityName} u where u.name like ?1% and u.age >= ?2")
    List<User> findByParam(String name, Integer age);

    /**
     * 根據名稱、年齡查詢用戶（使用 @Query 註解及 @Param 綁定參數）
     *
     * @param name 名稱
     * @param age  年齡
     * @return
     */
    @Query("select u from #{#entityName} u where u.name like :name% and u.age >= :age")
    List<User> findByParam2(@Param("name") String name, @Param("age") Integer age);

    /**
     * 查詢用戶數
     *
     * @return
     */
    @Query(nativeQuery = true, value = "select count(1) from user")
    long count();

    /**
     * 根據 id 更新用戶年齡
     *
     * @param id
     * @param age 年齡
     */
    @Modifying
    @Query("update User u set u.age = :age where u.id = :id")
    void updateById(@Param("id") Integer id, @Param("age") Integer age);

    /**
     * 根據 id 刪除用戶
     *
     * @param id
     */
    @Modifying
    @Query("delete from User u where u.id = :id")
    void deleteById(@Param("id") Integer id);
}

UserRepositoryTest

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.test.context.junit4.SpringJUnit4ClassRunner;

@RunWith(SpringJUnit4ClassRunner.class)
@SpringBootTest
public class UserRepositoryTest {

    @Autowired
    private UserRepository userRepository;

    @Test
    public void findByName() {
        System.out.println(userRepository.findByName("LeifChen"));
    }

    @Test
    public void findByMaxId() {
        System.out.println(userRepository.findByMaxId());
    }

    @Test
    public void findByParam() {
        System.out.println(userRepository.findByParam("Test", 20));
    }

    @Test
    public void findByParam2() {
        System.out.println(userRepository.findByParam2("Test", 20));
    }

    @Test
    public void count() {
        System.out.println(userRepository.count());
    }
}

UserService

import com.chen.repository.UserRepository;
import org.springframework.stereotype.Service;

import javax.transaction.Transactional;

@Service
public class UserService {

    private final UserRepository userRepository;

    public UserService(UserRepository userRepository) {
        this.userRepository = userRepository;
    }

    @Transactional(rollbackOn = Exception.class)
    public void updateById(Integer id, Integer age) {
        userRepository.updateById(id, age);
    }

    @Transactional(rollbackOn = Exception.class)
    public void deleteById(Integer id) {
        userRepository.deleteById(id);
    }
}

UserServiceTest

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.test.context.junit4.SpringJUnit4ClassRunner;

@RunWith(SpringJUnit4ClassRunner.class)
@SpringBootTest
public class UserServiceTest {

    @Autowired
    private UserService userService;

    @Test
    public void updateById() {
        userService.updateById(3, 28);
    }

    @Test
    public void deleteById() {
        userService.deleteById(3);
    }
}

比較

JDBC：代碼冗餘，需要手寫 SQL 語句，需要手工關閉連接，每次獲取連接和關閉連接會加大數據庫的負擔。
Spring JDBC：通過 Spring 管理連接池，需要手寫 SQL 語句，手動映射字段關係。
Spring Data JPA：通過 JPA 規範命名方法，不需要手寫 SQL 語句。

Spring Data JPA

Spring Data

傳統 JDBC

Spring JDBC

Spring Data JPA

Reposiroty 接口

JPA 方法關鍵字定義規則

註解

比較

參考

Redis入門

Redis擴展

Redis命令

Guava Cache 入門

【Spring入門-05】DispatcherServlet

Mac下配置sublime實現LaTeX

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