20165235 Make up after class in the eighth week

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20165235 Make up after class in the eighth week

Code Analysis of Textbook 11.1-11.10

  • Example11_1
import java.sql.*; 
public class Example11_1 {
   public static void main(String args[]) {
      Connection con=null;
      Statement sql; 
      ResultSet rs;
      try{  Class.forName("com.mysql.jdbc.Driver"); //加载JDBC_MySQL驱动
      }
      catch(Exception e){}
      String uri = "jdbc:mysql://localhost:3306/students?useSSL=true";
      String user ="root";
      String password ="";
      try{  
         con = DriverManager.getConnection(uri,user,password); //连接代码
      }
      catch(SQLException e){ }
      try { 
          sql=con.createStatement();
          rs=sql.executeQuery("SELECT * FROM mess"); //查询mess表
          while(rs.next()) {//当存在下一个数据是返回true
             String number=rs.getString(1);//将表第一列的数据传给number
             String name=rs.getString(2);
             Date date=rs.getDate(3);
             float height=rs.getFloat(4);
             System.out.printf("%s\t",number);
             System.out.printf("%s\t",name);
             System.out.printf("%s\t",date); 
             System.out.printf("%.2f\n",height);
          }
          con.close();//关闭连接
      }
      catch(SQLException e) { 
         System.out.println(e);
      }
  }
}
  • This code is used to query all records in the message table in the student database.
  • Example11_2
import java.sql.*; 
public class Example11_2 {
   public static void main(String args[]) {
      Connection con;
      Statement sql; 
      ResultSet rs;
      con = GetDBConnection.connectDB("students","root","");
      if(con == null ) return;
      try { 
          sql=con.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,
                                    ResultSet.CONCUR_READ_ONLY);
          rs = sql.executeQuery("SELECT * FROM mess ");
          rs.last();
          int max = rs.getRow();
          System.out.println("表共有"+max+"条记录,随机抽取2条记录：");
          int [] a =GetRandomNumber.getRandomNumber(max,2);//得到1-max之间2个不同随机数
          for(int i:a){
             rs.absolute(i);//油标移动到第i行
             String number = rs.getString(1);
             String name = rs.getString(2);
             Date date = rs.getDate(3);
             float h = rs.getFloat(4);
             System.out.printf("%s\t",number);
             System.out.printf("%s\t",name);
             System.out.printf("%s\t",date); 
             System.out.printf("%.2f\n",h);
          }
          con.close();
      }
      catch(SQLException e) { 
         System.out.println(e);
      }
  }
}
import java.sql.*; 
public class GetDBConnection {
   public static Connection connectDB(String DBName,String id,String p) {
      Connection con = null;
      String 
      uri = "jdbc:mysql://localhost:3306/"+DBName+"?useSSL=true&characterEncoding=utf-8";
      try{  Class.forName("com.mysql.jdbc.Driver");//加载JDBC-MySQL驱动
      }
      catch(Exception e){}
      try{  
         con = DriverManager.getConnection(uri,id,p); //连接代码
      }
      catch(SQLException e){}
      return con;
   }
}
import java.util.*;
public class GetRandomNumber {
   public static int [] getRandomNumber(int max,int amount) {
      //1-max之间的amount个不同随机整数
     int [] randomNumber = new int[amount];
     int index =0;
     randomNumber[0]= -1;
     Random random = new Random();
     while(index<amount){
       int number = random.nextInt(max)+1;
       boolean isInArrays=false;
       for(int m:randomNumber){//m依次取数组randomNumber元素的值（见3.7）
          if(m == number)
            isInArrays=true;  //number在数组里了
       }
       if(isInArrays==false){
           //如果number不在数组randomNumber中:
           randomNumber[index] = number;
           index++;   
       }
     }
     return  randomNumber;
   }
}

Separate the database in a GetDatabaseConnection class. Randomly query two records of the message table in the student database.

  • Example11_3
import java.sql.*; 
public class Example11_3 {
   public static void main(String args[]) {
      Connection con;
      Statement sql; 
      ResultSet rs;
      con = GetDBConnection.connectDB("students","root","");
      if(con == null ) return;
      String c1=" year(birthday)<=2000 and month(birthday)>7";//条件1
      String c2=" name Like '张_%'";
      String c3=" height >1.65";
      String sqlStr =
      "select * from mess where "+c1+" and "+c2+" and "+c3+"order by birthday";
      try { 
          sql=con.createStatement();
          rs = sql.executeQuery(sqlStr);
          while(rs.next()) { 
             String number=rs.getString(1);
             String name=rs.getString(2);
             Date date=rs.getDate(3);
             float height=rs.getFloat(4);
             System.out.printf("%s\t",number);
             System.out.printf("%s\t",name);
             System.out.printf("%s\t",date); 
             System.out.printf("%.2f\n",height);
          }
          con.close();
      }
      catch(SQLException e) { 
         System.out.println(e);
      }
  }
}
import java.sql.*; 
public class GetDBConnection {
   public static Connection connectDB(String DBName,String id,String p) {
      Connection con = null;
      String uri = 
     "jdbc:mysql://localhost:3306/"+DBName+"?useSSL=true&characterEncoding=utf-8";
      try{  Class.forName("com.mysql.jdbc.Driver");//加载JDBC-MySQL驱动
      }
      catch(Exception e){}
      try{  
         con = DriverManager.getConnection(uri,id,p); //连接代码
      }
      catch(SQLException e){}
      return con;
   }
}
  • This code is to query the students with the surname Zhang in the mess table, the height is greater than 16.5, the birth year is 2000 or before 2000, and the month is after July, and it is sorted by birth date.
  • Example11_4
import java.sql.*; 
public class Example11_4 {
   public static void main(String args[]) {
      Connection con;
      Statement sql; 
      ResultSet rs;
      con = GetDBConnection.connectDB("students","root","");
      if(con == null ) return;
      String jiLu="('R11q','王三','2000-10-23',1.66),"+
                  "('R10q','李武','1989-10-23',1.76)";    //2条记录
      String sqlStr ="insert into mess values"+jiLu;
      try { 
          sql=con.createStatement(); 
          int ok = sql.executeUpdate(sqlStr);
          rs = sql.executeQuery("select * from mess");
          while(rs.next()) { 
             String number=rs.getString(1);
             String name=rs.getString(2);
             Date date=rs.getDate(3);
             float height=rs.getFloat(4);
             System.out.printf("%s\t",number);
             System.out.printf("%s\t",name);
             System.out.printf("%s\t",date); 
             System.out.printf("%.2f\n",height);
          }
          con.close();
      }
      catch(SQLException e) { 
         System.out.println("记录中number值不能重复"+e);
      }
  }
}
  • This code inserts two records into the mess table.
  • Example11_5
import java.sql.*; 
public class Example11_5 {
   public static void main(String args[]) {
      Connection con;
      PreparedStatement preSql;  //预处理语句对象preSql
      ResultSet rs;
      con = GetDBConnection.connectDB("students","root","");
      if(con == null ) return;
      String sqlStr ="insert into mess values(?,?,?,?)";
      try { 
          preSql = con.prepareStatement(sqlStr);//得到预处理语句对象preSql
          preSql.setString(1,"A001");       //设置第1个?代表的值
          preSql.setString(2,"刘伟");       //设置第2个?代表的值
          preSql.setString(3,"1999-9-10"); //设置第3个?代表的值
          preSql.setFloat(4,1.77f);        //设置第4个?代表的值   
          int ok = preSql.executeUpdate();
          sqlStr="select * from mess where name like ? ";
          preSql = con.prepareStatement(sqlStr);//得到预处理语句对象preSql
          preSql.setString(1,"张%");       //设置第1个?代表的值
          rs = preSql.executeQuery();
          while(rs.next()) { 
             String number=rs.getString(1);
             String name=rs.getString(2);
             Date date=rs.getDate(3);
             float height=rs.getFloat(4);
             System.out.printf("%s\t",number);
             System.out.printf("%s\t",name);
             System.out.printf("%s\t",date); 
             System.out.printf("%.2f\n",height);
          }
          con.close();
      }
      catch(SQLException e) { 
         System.out.println("记录中number值不能重复"+e);
      }
  }
}
import java.sql.*; 
public class GetDBConnection {
   public static Connection connectDB(String DBName,String id,String p) {
      Connection con = null;
      String uri = 
     "jdbc:mysql://localhost:3306/"+DBName+"?useSSL=true&characterEncoding=utf-8";
      try{  Class.forName("com.mysql.jdbc.Driver");//加载JDBC-MySQL驱动
      }
      catch(Exception e){}
      try{  
         con = DriverManager.getConnection(uri,id,p); //连接代码
      }
      catch(SQLException e){}
      return con;
   }
}
  • This code uses prepared statements to add and query the record with the surname Zhang to the message table
  • Example11_6
  • import javax.swing.*;
public class Example11_6 {
   public static void main(String args[]) {
  String [] tableHead;
  String [][] content; 
  JTable table ;
  JFrame win= new JFrame();
  Query findRecord = new  Query();
  findRecord.setDatabaseName("students");
  findRecord.setSQL("select * from mess");
  content = findRecord.getRecord();
  tableHead=findRecord.getColumnName();
  table = new JTable(content,tableHead); 
  win.add(new JScrollPane(table));
  win.setBounds(12,100,400,200);
  win.setVisible(true); 
  win.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
   }
}
import java.sql.*;
public class Query {
   String databaseName="";      //数据库名
   String SQL;              //SQL语句
   String [] columnName;        //全部字段（列）名
   String [][] record;          //查询到的记录
   public Query() {
  try{  Class.forName("com.mysql.jdbc.Driver");//加载JDBC-MySQL驱动
  }
  catch(Exception e){}
   }
   public void setDatabaseName(String s) {
  databaseName=s.trim();
   }
   public void setSQL(String SQL) {
  this.SQL=SQL.trim();
   }
   public String[] getColumnName() {
   if(columnName ==null ){
       System.out.println("先查询记录");
       return null;
   }
   return columnName;
   }
   public String[][] getRecord() {
   startQuery();
   return record;
   }
   private void startQuery() { 
  Connection con;
  Statement sql;  
  ResultSet rs;
  String uri = 
 "jdbc:mysql://localhost:3306/"+
  databaseName+"?useSSL=true&characterEncoding=utf-8";
  try { 
    con=DriverManager.getConnection(uri,"root","");
    sql=con.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,
                            ResultSet.CONCUR_READ_ONLY);
    rs=sql.executeQuery(SQL);
    ResultSetMetaData metaData = rs.getMetaData();
    int columnCount = metaData.getColumnCount();//字段数目 
    columnName=new String[columnCount]; 
    for(int i=1;i<=columnCount;i++){
        columnName[i-1]=metaData.getColumnName(i);
    } 
    rs.last(); 
    int recordAmount =rs.getRow();  //结果集中的记录数目
    record = new String[recordAmount][columnCount];
    int i=0;
    rs.beforeFirst();
    while(rs.next()) { 
      for(int j=1;j<=columnCount;j++){
         record[i][j-1]=rs.getString(j); //第i条记录，放入二维数组的第i行
      }
      i++;
    }
    con.close();
  }
  catch(SQLException e) {
    System.out.println("请输入正确的表名"+e);
  }
   }    
}
  • The function of this code is to pass the database name and SQL statement to the object of the Query class.
  • Example11_7
import java.sql.*; 
public class Example11_7{
    public static void main(String args[]){
       Connection con = null;
       Statement sql;
       ResultSet rs; 
       String sqlStr;
       con = GetDBConnection.connectDB("students","root","");
       if(con == null ) return;
       try{ float n = 0.02f;
            con.setAutoCommit(false);       //关闭自动提交模式
            sql = con.createStatement();
            sqlStr = "select name,height from mess where number='R1001'";
            rs = sql.executeQuery(sqlStr);
            rs.next();
            float h1 = rs.getFloat(2);
            System.out.println("事务之前"+rs.getString(1)+"身高:"+h1);
            sqlStr = "select name,height from mess where number='R1002'"; 
            rs = sql.executeQuery(sqlStr);
            rs.next();
            float h2 = rs.getFloat(2);
            System.out.println("事务之前"+rs.getString(1)+"身高:"+h2);  
            h1 = h1-n;
            h2 = h2+n;
            sqlStr = "update mess set height ="+h1+" where number='R1001'";
            sql.executeUpdate(sqlStr);
            sqlStr = "update mess set height ="+h2+" where number='R1002'";
            sql.executeUpdate(sqlStr);
            con.commit(); //开始事务处理,如果发生异常直接执行catch块
            con.setAutoCommit(true); //恢复自动提交模式
            String s = "select name,height from mess"+
                      " where number='R1001'or number='R1002'";
            rs = 
            sql.executeQuery(s);
            while(rs.next()){
               System.out.println("事务后"+rs.getString(1)+
                                  "身高:"+rs.getFloat(2));  
            }
            con.close();
         }
         catch(SQLException e){
            try{ con.rollback();          //撤销事务所做的操作
            }
            catch(SQLException exp){}
         }
    }
}
import java.sql.*; 
public class GetDBConnection {
   public static Connection connectDB(String DBName,String id,String p) {
      Connection con = null;
      String uri = 
     "jdbc:mysql://localhost:3306/"+DBName+"?useSSL=true&characterEncoding=utf-8";
      try{  Class.forName("com.mysql.jdbc.Driver");//加载JDBC-MySQL驱动
      }
      catch(Exception e){}
      try{  
         con = DriverManager.getConnection(uri,id,p); //连接代码
      }
      catch(SQLException e){}
      return con;
   }
}
  • The function of this code is to reduce the height value of the number field R1001 in the message table by n, and add the reduced n to the height of the field R1002.
  • Example11_8
import java.sql.*;
public class Example11_8 {
   public static void main(String[] args) {
      Connection con =null;
      Statement sta = null;
      ResultSet rs;
      String SQL;
      try { 
        Class.forName("org.apache.derby.jdbc.EmbeddedDriver");//加载驱动
      }
      catch(Exception e) {
        System.out.println(e);  
        return;
      }
      try { 
         String uri ="jdbc:derby:students;create=true";
         con=DriverManager.getConnection(uri);  //连接数据库
         sta = con.createStatement();
      }
      catch(Exception e) {
        System.out.println(e);  
        return;
      }
      try { SQL = "create table chengji(name varchar(40),score float)";
            sta.execute(SQL);//创建表
      }
      catch(SQLException e) { 
         //System.out.println("该表已经存在"); 
      }
      SQL ="insert into chengji values"+
            "('张三', 90),('李斯', 88),('刘二', 67)";
      try {
         sta.execute(SQL);
         rs = sta.executeQuery("select * from chengji "); // 查询表中的记录
         while(rs.next()) {
            String name=rs.getString(1);
            System.out.print(name+"\t");
            float score=rs.getFloat(2);
            System.out.println(score);
         }
         con.close();
      } 
      catch(SQLException e) {
          System.out.println(e);  
      }
  }
}
  • The function of this code is to use the Derby database system to create a database named student, and create a chengji table in the database

  • Programming topics in Chapter 11 of the textbook

  • Programming Question 1

    import java.sql.*;
public class BianCheng1 {
public static void main(String args[]) {
    Connection con;
    Statement sql;
    ResultSet rs;
    con = GetDBConnection.connectDB("students","root",""); 
    if(con == null ) return;
    String sqlStr =
            "select * from mess "+"order by birthday";

    try {
        sql=con.createStatement();
        rs = sql.executeQuery(sqlStr);
        while(rs.next()) {
            String number=rs.getString(1);
            String name=rs.getString(2);
            Date date=rs.getDate(3);
            float height=rs.getFloat(4);
            System.out.printf("%s\t",number);
            System.out.printf("%s\t",name);
            System.out.printf("%s\t",date);
            System.out.printf("%.2f\n",height);
        }
        con.close();
    }
    catch(SQLException e) {
        System.out.println(e);
    }
}
}
class GetDBConnection {
   public static Connection connectDB(String DBName,String id,String p) {
  Connection con = null;
  String 
  uri = "jdbc:mysql://localhost:3306/"+DBName+"?useSSL=true&characterEncoding=utf-8";
  try{  Class.forName("com.mysql.jdbc.Driver");//加载JDBC-MySQL驱动
  }
  catch(Exception e){}
  try{  
     con = DriverManager.getConnection(uri,id,p); //连接代码
  }
  catch(SQLException e){}
  return con;
   }
}

  • Programming Question 2

    import javax.management.Query;
import javax.swing.*;
public class BianCheng2 {
public static void main (String args[]) {
    String [] tableHead;
    String [] content;
    JTable table;
    JFrame win= new JFrame();
    Query findRecord = new Query();
    findRecord.setDatabaseName(args[0]);
    findRecord.setSQL("select * from "+args[1]);
    content = findRecord.getRecord();
    tableHead=findRecord.getColumnName();
    table = new JTable(content,tableHead);
    win.add(new JScrollPane(table));
    win.setBounds(12,100,400,200);
    win.setVisible(true);
    win.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
}
 class Query {
   String databaseName="";       
   String SQL;               
   String [] columnName;        
   String [][] record;           
   public Query() {
  try{  Class.forName("com.mysql.jdbc.Driver"); 
  }
  catch(Exception e){}
   }
   public void setDatabaseName(String s) {
  databaseName=s.trim();
   }
   public void setSQL(String SQL) {
  this.SQL=SQL.trim();
   }
   public String[] getColumnName() {
   if(columnName ==null ){
       System.out.println("先查询记录");
       return null;
   }
   return columnName;
   }
   public String[][] getRecord() {
   startQuery();
   return record;
   }
   private void startQuery() { 
  Connection con;
  Statement sql;  
  ResultSet rs;
  String uri = 
 "jdbc:mysql://localhost:3306/"+
  databaseName+"?useSSL=true&characterEncoding=utf-8";
  try { 
    con=DriverManager.getConnection(uri,"root","");
    sql=con.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,
                            ResultSet.CONCUR_READ_ONLY);
    rs=sql.executeQuery(SQL);
    ResultSetMetaData metaData = rs.getMetaData();
    int columnCount = metaData.getColumnCount();//字段数目 
    columnName=new String[columnCount]; 
    for(int i=1;i<=columnCount;i++){
        columnName[i-1]=metaData.getColumnName(i);
    } 
    rs.last(); 
    int recordAmount =rs.getRow();   
    record = new String[recordAmount][columnCount];
    int i=0;
    rs.beforeFirst();
    while(rs.next()) { 
      for(int j=1;j<=columnCount;j++){
         record[i][j-1]=rs.getString(j); 
      }
      i++;
    }
    con.close();
  }
  catch(SQLException e) {
    System.out.println("请输入正确的表名"+e);
  }
   }    
}

  • Code cloud code link

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