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SpringBoot連接MYSQL數(shù)據(jù)庫并使用JPA進(jìn)行操作

更新時(shí)間：2017年04月18日 11:55:13 作者：wolzq

今天給大家介紹一下如何SpringBoot中連接Mysql數(shù)據(jù)庫，并使用JPA進(jìn)行數(shù)據(jù)庫的相關(guān)操作。

步驟一：在pom.xml文件中添加MYSQl和JPA的相關(guān)Jar包依賴，具體添加位置在dependencies中，具體添加的內(nèi)容如下所示。

<!--數(shù)據(jù)庫相關(guān)配置--> 
    <dependency> 
      <groupId>org.springframework.boot</groupId> 
      <artifactId>spring-boot-starter-web</artifactId> 
    </dependency> 
    <dependency> 
      <groupId>org.springframework.boot</groupId> 
      <artifactId>spring-boot-starter-data-jpa</artifactId> 
    </dependency> 
    <dependency> 
      <groupId>mysql</groupId> 
      <artifactId>mysql-connector-java</artifactId> 
    </dependency> 
    <dependency> 
      <groupId>org.apache.poi</groupId> 
      <artifactId>poi</artifactId> 
      <version>3.11</version> 
    </dependency>

步驟二：在application.properties配置文件中加入數(shù)據(jù)庫的相關(guān)配置，配置信息如下所示。

spring.datasource.url = jdbc:mysql://localhost:3306/webtest 
spring.datasource.username = root 
spring.datasource.password = 220316 
spring.datasource.driverClassName = com.mysql.jdbc.Driver 
# Specify the DBMS 
spring.jpa.database = MYSQL 
# Show or not log for each sql query 
spring.jpa.show-sql = true 
# Hibernate ddl auto (create, create-drop, update) 
spring.jpa.hibernate.ddl-auto = update 
# Naming strategy 
spring.jpa.hibernate.naming-strategy = org.hibernate.cfg.ImprovedNamingStrategy 
# stripped before adding them to the entity manager) 
spring.jpa.properties.hibernate.dialect = org.hibernate.dialect.MySQL5Dialect

這里給大家解釋一下：webtest代表數(shù)據(jù)庫名稱、root是用戶名、220316是密碼

步驟三：編寫數(shù)據(jù)庫操作的實(shí)體類，實(shí)體類具體信息如下所示：

package example.entity; 
import javax.persistence.*; 
import javax.validation.constraints.NotNull; 
import java.math.BigDecimal; 
import java.util.Date; 
@Entity 
@Table(name = "user") 
public class User { 
  @Id 
  @GeneratedValue(strategy = GenerationType.AUTO) 
  private int id; 
 
  @Column(name = "name", nullable = true, length = 30) 
  private String name; 
 
  @Column(name = "height", nullable = true, length = 10) 
  private int height; 
 
  @Column(name = "sex", nullable = true, length = 2) 
  private char sex; 
 
  @Temporal(TemporalType.DATE) 
  private Date birthday; 
 
  @Temporal(TemporalType.TIMESTAMP) 
  private Date sendtime; // 日期類型，格式：yyyy-MM-dd HH:mm:ss 
 
  @Column(name = "price", nullable = true, length = 10) 
  private BigDecimal price; 
 
  @Column(name = "floatprice", nullable = true, length = 10) 
  private float floatprice; 
 
 
  @Column(name = "doubleprice", nullable = true, length = 10) 
  private double doubleprice; 
 
  public Date getSendtime() { 
    return sendtime; 
  } 
 
  public void setSendtime(Date sendtime) { 
    this.sendtime = sendtime; 
  } 
 
  public BigDecimal getPrice() { 
    return price; 
  } 
 
  public void setPrice(BigDecimal price) { 
    this.price = price; 
  } 
 
  public float getFloatprice() { 
    return floatprice; 
  } 
 
  public void setFloatprice(float floatprice) { 
    this.floatprice = floatprice; 
  } 
 
  public double getDoubleprice() { 
    return doubleprice; 
  } 
 
  public void setDoubleprice(double doubleprice) { 
    this.doubleprice = doubleprice; 
  } 
 
  public User() { } 
 
  public char getSex() { 
    return sex; 
  } 
 
  public void setSex(char sex) { 
    this.sex = sex; 
  } 
 
  public Date getBirthday() { 
    return birthday; 
  } 
 
  public void setBirthday(Date birthday) { 
    this.birthday = birthday; 
  } 
 
  public User(int id) { 
    this.id = id; 
  } 
 
  public int getId() { 
    return id; 
  } 
 
  public void setId(int id) { 
    this.id = id; 
  } 
 
  public String getName() { 
    return name; 
  } 
 
  public void setName(String name) { 
    this.name = name; 
  } 
 
  public int getHeight() { 
    return height; 
  } 
 
  public void setHeight(int height) { 
    this.height = height; 
  } 
}

大家這里需要注意的是：實(shí)體類中的類名和字段屬性都要和數(shù)據(jù)庫中表和字段相互對應(yīng)。下面給出一張MYSQL-JAVA各種屬性的對應(yīng)關(guān)系圖：

步驟四：編寫dao層的數(shù)據(jù)操作類，dao數(shù)據(jù)操作類如下所示：

package example.dao; 
import example.entity.User; 
import org.springframework.data.repository.CrudRepository; 
import javax.transaction.Transactional; 
import java.math.BigDecimal; 
import java.util.Date; 
import java.util.List; 
 
@Transactional 
public interface UserDao extends CrudRepository<User, Integer> { 
  public List<User> findByName(String name); 
  public List<User> findBySex(char sex); 
  public List<User> findByBirthday(Date birthday); 
  public List<User> findBySendtime(Date sendtime); 
  public List<User> findByPrice(BigDecimal price); 
  public List<User> findByFloatprice(float floatprice); 
  public List<User> findByDoubleprice(double doubleprice); 
}

大家這里可能會有疑問，為什么要繼承CrudRepository<User, Integer>，具體有什么作用呢？

我這里給大家簡單的介紹一下JPA中一些常用的用法和使用準(zhǔn)則：

1.首先就是要繼承CrudRepository這個(gè)方法，里面包含的兩個(gè)參數(shù)的具體含義是：第一個(gè)參數(shù)表示所操作的實(shí)體類名稱，第二個(gè)參數(shù)表示實(shí)體類中主鍵的類型。

2.繼承完之后就可以使用一些繼承自父類的方法了，比如上面所示可以使用findBy+“你要查詢的字段名稱”，通過這樣的方法就可以輕輕松松實(shí)現(xiàn)SQL查詢的功能了。

說道這里可能大家還是有點(diǎn)迷糊，給大家舉一個(gè)例子就知道了：

例如上面的findByName（String name）其實(shí)等價(jià)于SQL語句中的 select *from user where name=？。這樣一對比大家是不是馬上就清楚這個(gè)方法到底代表什么含義了吧。

步驟五：編寫controller這個(gè)控制類，控制類具體信息如下所示：

package example.controller; 
import example.dao.UserDao; 
import example.entity.User; 
import org.springframework.beans.factory.annotation.Autowired; 
import org.springframework.stereotype.Controller; 
import org.springframework.web.bind.annotation.RequestMapping; 
import org.springframework.web.bind.annotation.ResponseBody; 
import java.math.BigDecimal; 
import java.text.ParseException; 
import java.text.SimpleDateFormat; 
import java.util.Date; 
import java.util.List; 
@Controller 
public class UserController { 
  @Autowired 
  private UserDao userDao; 
  @RequestMapping("/getName") 
  @ResponseBody 
  public String getByName(String name) { 
    List<User> userList = userDao.findByName(name); 
    if (userList != null && userList.size()!=0) { 
      return "The user length is: " + userList.size(); 
    } 
    return "user " + name + " is not exist."; 
  } 
 
  @RequestMapping("/getSex") 
  @ResponseBody 
  public String getBySex(char sex) { 
    List<User> userList = userDao.findBySex(sex); 
    if (userList != null && userList.size()!=0) { 
      return "The user length is: " + userList.size(); 
    } 
    return "user " + sex + " is not exist."; 
  } 
 
  @RequestMapping("/getBirthday") 
  @ResponseBody 
  public String findByBirthday(String birthday) { 
    System.out.println("birthday:"+birthday); 
    SimpleDateFormat formate=new SimpleDateFormat("yyyy-MM-dd"); 
    List<User> userList = null; 
    try { 
      userList = userDao.findByBirthday(formate.parse(birthday)); 
    } catch (ParseException e) { 
      e.printStackTrace(); 
    } 
    if (userList != null && userList.size()!=0) { 
      return "The user length is: " + userList.size(); 
    } 
    return "user " + birthday + " is not exist."; 
  } 
 
  @RequestMapping("/getSendtime") 
  @ResponseBody 
  public String findBySendtime(String sendtime) { 
    System.out.println("sendtime:"+sendtime); 
    SimpleDateFormat formate=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"); 
    List<User> userList = null; 
    try { 
      userList = userDao.findBySendtime(formate.parse(sendtime)); 
    } catch (ParseException e) { 
      e.printStackTrace(); 
    } 
    if (userList != null && userList.size()!=0) { 
      return "The user length is: " + userList.size(); 
    } 
    return "user " + sendtime + " is not exist."; 
  } 
 
  @RequestMapping("/getPrice") 
  @ResponseBody 
  public String findByPrice(BigDecimal price) { 
    List<User> userList = null; 
    userList = userDao.findByPrice(price); 
    if (userList != null && userList.size()!=0) { 
      return "The user length is: " + userList.size(); 
    } 
    return "user " + price + " is not exist."; 
  } 
 
  @RequestMapping("/getFloatprice") 
  @ResponseBody 
  public String findFloatprice(float floatprice) { 
    List<User> userList = null; 
    userList = userDao.findByFloatprice(floatprice); 
    if (userList != null && userList.size()!=0) { 
      return "The user length is: " + userList.size(); 
    } 
    return "user " + floatprice + " is not exist."; 
  } 
 
  @RequestMapping("/getDoubleprice") 
  @ResponseBody 
  public String findByPrice(double doubleprice) { 
    List<User> userList = null; 
    userList = userDao.findByDoubleprice(doubleprice); 
    if (userList != null && userList.size()!=0) { 
      return "The user length is: " + userList.size(); 
    } 
    return "user " + doubleprice + " is not exist."; 
  } 
}

大家這里可能會有一個(gè)很大的疑問，我當(dāng)初也對這個(gè)問題深深的不理，那就是userDao沒有實(shí)例化為什么能夠直接使用呢？

現(xiàn)在我就為大家解釋一下為什么會這樣：

其實(shí)不是這個(gè)userDao沒有實(shí)例化，只是實(shí)例化是由系統(tǒng)自動完成的。只要在userDao的上方添加@Autowired屬性就可以實(shí)現(xiàn)接口自動的實(shí)例化了，完全不需要像以前一樣需要去寫什么userDaoImp之類的實(shí)現(xiàn)類了。這樣做就可以大大的挺高代碼的簡易程度，開發(fā)速度大大的挺高。

我知道現(xiàn)在可能還會有人問這樣一個(gè)問題：那就是自動實(shí)例化了，可是實(shí)例化怎么知道dao類要實(shí)現(xiàn)什么的增刪改查的功能呀，dao代碼里面壓根就沒說啊？其實(shí)有心人可能已經(jīng)發(fā)現(xiàn)了，上一步的時(shí)候我們解釋了一下findBy+“字段名”的具體作用是什么，這其實(shí)就是這個(gè)問題的答案。其實(shí)dao層中各種方法就是daoimp中各種實(shí)現(xiàn)類中的SQl命令，具體是怎么對應(yīng)的我會再下一節(jié)中給大家詳細(xì)的介紹一下，現(xiàn)在先賣個(gè)關(guān)子。

步驟六：數(shù)據(jù)庫的表名和字段信息如下所示：