Wie verwende ich die Datenbank zum Hinzufügen, Löschen, Überprüfen und Ändern von Vorgängen in Java und Scala?-javaLernprogramm-php.cn

添加jar包

这里的Scala不是maven工程所以要找到项目结构（快捷键：同时按住Ctrl+shift+Alt+s）在模块里面添加添加MySQL的jar包，如果是Maven工程可以直接在pom里面直接加即可

Wie verwende ich die Datenbank zum Hinzufügen, Löschen, Überprüfen und Ändern von Vorgängen in Java und Scala?

实现操作数据库需要两个类，一个用于测试的Demo，一个用于实现增删查改的Util方法

在MysqlDemo在这里需要用到伴生类和伴生对象，伴生类主要是实现连接数据库

class MysqlDemo {
  //  连接数据库 底层原理还是jdbc
  //驱动名称
  var driver = "com.mysql.cj.jdbc.Driver"
  //  访问MySQL服务器，通过3306端口访问mysql数据库
  var url = "jdbc:mysql://192.168.152.184:3306/exam"
  //用户名
  var user = "root"
  //密码
  var password = "123456"
  //辅助构造器
  def this(driver: String, url: String, user: String, pwd: String) {
    this()
    this.driver = driver
    this.url = url
    this.user = user
    this.password = pwd
  }
}

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伴生对象则主要是实现操作数据库，需要先实现apply方法，主函数里面创建对象调用apply方法，调用连接方法和释放资源

object MysqlDemo {
  //  实现apply方法
  def apply(): MysqlDemo = new MysqlDemo()
  def apply(driver: String, url: String, user: String, pwd: String): MysqlDemo = new MysqlDemo(driver, url, user, pwd)
  def main(args: Array[String]): Unit = {
    //创建对象，调用apply方法
    val demo = MysqlDemo()
    //导入MySQLUtil包
    import MysqlUtil._
    //调用创建连接的方法
    demo.conn()
    // 调用释放资源方法
    demo.close(connection)
/**操作数据库代码*/
}

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Util则需要先初始化数据库连接，注册驱动，得到数据库连接，释放资源

import java.sql.{Connection, DriverManager, PreparedStatement, ResultSet}
object MysqlUtil {
  implicit class MysqlOp(obj: MysqlDemo) {
    //初始化数据连接
    private var connection: Connection = _
    def conn(): Connection = {
      //注册driver
      Class.forName(obj.driver)
      //得到数据库连接
      val connection: Connection = DriverManager.getConnection(obj.url, obj.user, obj.password)
      connection
    }
    //释放资源
    def close(conn: Connection): Unit = {
      if (conn != null) {
        conn.close()
      }
    }
}

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准备工作已做完下面要实现对数据库的增删查改

添加数据

方法一

//Util代码
//添加数据方法一
    def insertStudent: Int = {
      val insertSqlStr = "insert into student(name, age, gender, telephone, email, classid)" +
        "values (&#39;周七&#39;, 6, &#39;男&#39;, &#39;13888888888&#39;, &#39;346497@qq.com&#39;, 2)"
      val i: Int = conn().createStatement.executeUpdate(insertSqlStr)
      i
    }
//Demo测试代码
 //添加数据方法一
    val i: Int = demo.insertStudent
    if (i == 1) {
      println("添加成功")
    } else if (i == 0) {
      println("添加失败")
    }

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方法二

//Util代码  
   //添加数据方法二
    def insertStudent(name: String, age: Int, gender: String, telephone: String, email: String, classid: Int): Int = {
      val insertSqlStr = "insert into student(id,name, age, gender, telephone, email, classid)" +
        "values (null,?,?,?,?,?,?)"
      val preStmt: PreparedStatement = conn().prepareStatement(insertSqlStr)
      preStmt.setString(1, name)
      preStmt.setInt(2, age)
      preStmt.setString(3, gender)
      preStmt.setString(4, telephone)
      preStmt.setString(5, email)
      preStmt.setInt(6, classid)
      val i: Int = preStmt.executeUpdate()
      i
    }
//Demo测试代码
 //添加数据方法二
    val i: Int = demo.insertStudent("aaa", 18, "男", "12345678910", "34649756@qq.com", 1)
    if (i == 1) {
      println("添加成功")
    } else if (i == 0) {
      println("添加失败")
    }

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删除数据

//Util代码
  def deleteStudent(id: Int): Int = {
      val deleteSql = "delete from student where id= ?"
      val preStmt: PreparedStatement = conn().prepareStatement(deleteSql)
      preStmt.setInt(1, id)
      val i: Int = preStmt.executeUpdate()
      i
    }
//Demo测试代码
        val i: Int = demo.deleteStudent(21)
        if (i == 1) {
          println("删除成功")
        } else if (i == 0) {
          println("删除失败")
        }

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查询数据

//Util代码
   def selectStudent: Unit = {
      val selectSql = "select id,name, age, gender, telephone, email, classid from student"
      val rs: ResultSet = conn().createStatement().executeQuery(selectSql)
      println("学号\t姓名\t年龄\t性别\t手机号\t邮箱\t班级编号")
      while (rs.next()) {
        val id: Int = rs.getInt("id")
        val name: String = rs.getString("name")
        val age: Int = rs.getInt("age")
        val gender: String = rs.getString("gender")
        val telephone: String = rs.getString("telephone")
        val email: String = rs.getString("email")
        val classid: String = rs.getString("classid")
        println(id + "\t" + name + "\t" + age + "\t" + gender + "\t" + telephone + "\t" + email + "\t" + classid)
      }
    }
//Demo测试代码
        demo.selectStudent

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修改数据

//Util代码
   def updateStudent(id: Int, name: String, age: Int, gender: String, telephone: String, email: String, classid: Int): Int = {
      val updateSql = "update student set name=?," + "age=?, " + "gender=?," +
        "telephone=?," + "email=?, " + "classid=? where id=?"
      val preStmt: PreparedStatement = conn().prepareStatement(updateSql)
      preStmt.setString(1, name)
      preStmt.setInt(2, age)
      preStmt.setString(3, gender)
      preStmt.setString(4, telephone)
      preStmt.setString(5, email)
      preStmt.setInt(6, classid)
      preStmt.setInt(7, id)
      val i: Int = preStmt.executeUpdate()
      i
    }
//Demo测试代码
        val i: Int = demo.updateStudent(22, "test", 25, "女", "123456789", "369852@qq.com", 2)
        if (i == 1) {
          println("修改成功")
        } else if (i == 0) {
          println("修改失败")
        }

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完整代码

MysqlUtil代码

import java.sql.{Connection, DriverManager, PreparedStatement, ResultSet}
object MysqlUtil {
  implicit class MysqlOp(obj: MysqlDemo) {
    //初始化数据连接
    private var connection: Connection = _
    def conn(): Connection = {
      //注册driver
      Class.forName(obj.driver)
      //得到数据库连接
      val connection: Connection = DriverManager.getConnection(obj.url, obj.user, obj.password)
      connection
    }
    //释放资源
    def close(conn: Connection): Unit = {
      if (conn != null) {
        conn.close()
      }
    }
    //添加数据方法一
    def insertStudent: Int = {
      val insertSqlStr = "insert into student(name, age, gender, telephone, email, classid)" +
        "values (&#39;bbb&#39;, 6, &#39;男&#39;, &#39;13852277346&#39;, &#39;3464975236@qq.com&#39;, 2)"
      val i: Int = conn().createStatement.executeUpdate(insertSqlStr)
      i
    }
    //添加数据方法二
    def insertStudent(name: String, age: Int, gender: String, telephone: String, email: String, classid: Int): Int = {
      val insertSqlStr = "insert into student(id,name, age, gender, telephone, email, classid)" +
        "values (null,?,?,?,?,?,?)"
      val preStmt: PreparedStatement = conn().prepareStatement(insertSqlStr)
      preStmt.setString(1, name)
      preStmt.setInt(2, age)
      preStmt.setString(3, gender)
      preStmt.setString(4, telephone)
      preStmt.setString(5, email)
      preStmt.setInt(6, classid)
      val i: Int = preStmt.executeUpdate()
      i
    }
    //删除数据
    def deleteStudent(id: Int): Int = {
      val deleteSql = "delete from student where id= ?"
      val preStmt: PreparedStatement = conn().prepareStatement(deleteSql)
      preStmt.setInt(1, id)
      val i: Int = preStmt.executeUpdate()
      i
    }
    //修改数据
    def updateStudent(id: Int, name: String, age: Int, gender: String, telephone: String, email: String, classid: Int): Int = {
      val updateSql = "update student set name=?," + "age=?, " + "gender=?," +
        "telephone=?," + "email=?, " + "classid=? where id=?"
      val preStmt: PreparedStatement = conn().prepareStatement(updateSql)
      preStmt.setString(1, name)
      preStmt.setInt(2, age)
      preStmt.setString(3, gender)
      preStmt.setString(4, telephone)
      preStmt.setString(5, email)
      preStmt.setInt(6, classid)
      preStmt.setInt(7, id)
      val i: Int = preStmt.executeUpdate()
      i
    }
    //查询数据
    def selectStudent: Unit = {
      val selectSql = "select id,name, age, gender, telephone, email, classid from student"
      val rs: ResultSet = conn().createStatement().executeQuery(selectSql)
      println("学号\t姓名\t年龄\t性别\t手机号\t邮箱\t班级编号")
      while (rs.next()) {
        val id: Int = rs.getInt("id")
        val name: String = rs.getString("name")
        val age: Int = rs.getInt("age")
        val gender: String = rs.getString("gender")
        val telephone: String = rs.getString("telephone")
        val email: String = rs.getString("email")
        val classid: String = rs.getString("classid")
        println(id + "\t" + name + "\t" + age + "\t" + gender + "\t" + telephone + "\t" + email + "\t" + classid)
      }
    }
  }
}

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MysqlDemo代码

import java.sql.Connection
class MysqlDemo {
  //  连接数据库 底层原理还是jdbc
  //驱动名称
  var driver = "com.mysql.cj.jdbc.Driver"
  //  访问MySQL服务器，通过3306端口访问mysql数据库
  var url = "jdbc:mysql://192.168.152.184:3306/exam"
  //用户名
  var user = "root"
  //密码
  var password = "123456"
  //辅助构造器    
  def this(driver: String, url: String, user: String, pwd: String) {
    this()
    this.driver = driver
    this.url = url
    this.user = user
    this.password = pwd
  }
}
object MysqlDemo {
  //  实现apply方法
  def apply(): MysqlDemo = new MysqlDemo()
  def apply(driver: String, url: String, user: String, pwd: String): MysqlDemo = new MysqlDemo(driver, url, user, pwd)
  def main(args: Array[String]): Unit = {
    //创建对象，调用apply方法
    val demo = MysqlDemo()
    //导入MySQLUtil包
    import MysqlUtil._
    //调用创建连接的方法
    val connection: Connection = demo.conn()
    // 调用释放资源方法
    demo.close(connection)
    //添加数据方法一
    val i: Int = demo.insertStudent
    if (i == 1) {
      println("添加成功")
    } else if (i == 0) {
      println("添加失败")
    }
    //添加数据方法二
    val i: Int = demo.insertStudent("aaa", 18, "男", "12345678910", "34649756@qq.com", 1)
    if (i == 1) {
      println("添加成功")
    } else if (i == 0) {
      println("添加失败")
    }
    //查询数据
    demo.selectStudent
    // 修改数据
    val i: Int = demo.updateStudent(22, "test", 25, "女", "123456789", "369852@qq.com", 2)
    if (i == 1) {
      println("修改成功")
    } else if (i == 0) {
      println("修改失败")
    }
    //删除数据
    val i: Int = demo.deleteStudent(21)
    if (i == 1) {
      println("删除成功")
    } else if (i == 0) {
      println("删除失败")
    }
  }
}

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