JDBC Six section-1

Create a db.properties file to configure access to the database dbname=mysql/oracle//by reading the file to achieve different access to different databases import Java.io.*;import java.util.*; public class Jdbctestprogrammer1{public static void Main (string[] args) throws exception{// Read the configuration file via FileReader filereader reader = new FileReader ("db.properties");//Create a Property object Properties Prop = new properties ();// Read reader to memory via the Property object's Load method to generate a map collection prop.load (reader);//Close stream reader.close ();//GetProperty via Property object (string key) string dbname = Prop.getproperty ("dbname");//created by the Java reflection Mechanism Class C = Class.forName (dbname); Object obj = C.newinstance (); JDBC jdbc = (JDBC) obj;jdbc.getconnection ();}}

JDBC Programming Six steps

1: Registered Driver

2: Get a database connection

3: Execute database Operation object

4: Execute SQL statement

5: Working with query result sets

6: Close Resource

The first step: Implement the registration drive

1.1) Get the Drive object

1.2) Registration Drive

Import Java.sql.driver;import Java.sql.drivermanager;public class Drivertest {public static void main (string[] args) { try{//gets the Drive object driver Driver = new Com.mysql.jdbc.Driver ();//Register drive Drivermanager.registerdriver (driver);} catch (Exception e) {e.printstacktrace ();}}}

Step two: Get the connection to the database

Import Java.sql.connection;import Java.sql.driver;import Java.sql.drivermanager;public class JDBCTest {public static void Main (string[] args) {try{//1.1 Gets the drive object driver Driver = new Com.mysql.jdbc.Driver ();// 1.2 Registered driver Drivermanager.registerdriver (driver);//2 Gets the database connection string url = "Jdbc:mysql://127.0.0.1:3306/test"; String user = "root"; String password = "123456"; Connection conn = drivermanager.getconnection (URL, user, password); SYSTEM.OUT.PRINTLN (conn);} catch (Exception e) {e.printstacktrace ();}}}

Step three: Get the Operation object of the database

Import Java.sql.driver;import java.sql.drivermanager;import Java.sql.statement;import java.sql.Connection;public Class Jdbctest{public static void Main (string[] args) {try{//registered drive Driver Driver = new Com.mysql.jdbc.Driver ();D Rivermanag Er.registerdriver (driver);//Get database connection string url = "Jdbc:mysql://127.0.0.1:3306/test"; String user = "root"; String password = "123456"; Connection conn = drivermanager.getconnection (Url,user,password);//3: Gets the database operation object Statement stmt = Conn.createstatement ( ); System.out.println (stmt);} catch (Exception e) {e.printstacktrace ();}}}

Fourth step: Execute the SQL statement

import java.sql.connection;import java.sql.driver;import java.sql.drivermanager;import  java.sql.resultset;import java.sql.sqlexception;import java.sql.statement;public class  Jdbctest{public static void main (String[] args) {TRY {//1 registered driver driver driver =  new com.mysql.jdbc.driver ();D rivermanager.deregisterdriver (Driver);//2 Get database connection string url =   "JDBC:MYSQL://127.0.0.1:3306/JDBC"; string user =  "Root"; string password =  "123456"; Connection conn = drivermanager.getconnection (Url, user, password); SYSTEM.OUT.PRINTLN (conn);//3 Gets the database Operation Object Statement stat = conn.createstatement ();//4 Execute SQL statement: DQL statement- > Query string sql =  "select c_id, c_name , c_zip  from  Customers "; Resultset rs = stat.executequery (SQL); System.out.println (RS);} catch  (sqlexception e)  {e.printstacktraCE ();}}} 

Fifth step: Working with query result sets

import java.sql.connection;import java.sql.driver;import java.sql.drivermanager;import  java.sql.resultset;import java.sql.sqlexception;import java.sql.statement;public class  Jdbctest{public static void main (String[] args) {TRY {//1 registered driver driver driver =  new com.mysql.jdbc.driver ();D rivermanager.deregisterdriver (Driver);//2 Get database connection string url =   "JDBC:MYSQL://127.0.0.1:3306/JDBC"; string user =  "Root"; string password =  "123456"; Connection conn = drivermanager.getconnection (Url, user, password); SYSTEM.OUT.PRINTLN (conn);//3 Gets the database Operation Object Statement stat = conn.createstatement ();//4 Execute SQL statement: DQL statement- > Query string sql =  "select c_id, c_name , c_zip  from  Customers; "; Resultset rs = stat.executequery (SQL); System.out.println (RS);//5 processing Query results while (Rs.next ()) {//fetching data the first way string   Name= rs.getstring ("C_name"); Int id = rs.getint ("c_id");d ouble zip =  Rs.getdouble ("C_zip"); System.out.println (name+ "\t " +id+ "\t " +zip);/* Do not suggest the following wording, program readability is not strong string  name=  Rs.getstring (2); Int id = rs.getint (1);d ouble zip = rs.getdouble (3); System.out.println (name+ "\t " +id+ "\t " +zip);*/}}catch  (sqlexception e)  { E.printstacktrace ();}}}

Sixth step: Close Resources

Variables defined in the try cannot be read in finally because of the variable scope relationship, so local variables are required as global variables

import java.sql.connection;import java.sql.driver;import java.sql.drivermanager;import  java.sql.resultset;import java.sql.sqlexception;import java.sql.statement;public class  Jdbctest{public static void main (String[] args) {connection conn = null; statement stat = null; RESULTSET RS = NULL;TRY {//1 Registered Driver driver driver = new  Com.mysql.jdbc.Driver ();D rivermanager.deregisterdriver (Driver);//2 Get database connection string url =  "JDBC: Mysql://127.0.0.1:3306/jdbc "; string user =  "Root"; string password =  "123456"; Conn = drivermanager.getconnection (url, user,  password); SYSTEM.OUT.PRINTLN (conn);//3 Gets the database Operation Object Stat = conn.createstatement ();//4 Execute SQL statement: DQL statement, query string  sql =  "select c_id, c_name , c_zip  from customers;"; Rs = stat.executequery (SQL); System.out.prIntln (RS);//5 processing Query results while (Rs.next ()) {//fetching data in the first way string  name= rs.getstring ("C_name"); int id  = rs.getint ("c_id");d ouble zip = rs.getdouble ("C_zip"); System.out.println (name+ "\t " +id+ "\t " +zip);/* Do not suggest the following wording, program readability is not strong string  name=  Rs.getstring (2); Int id = rs.getint (1);d ouble zip = rs.getdouble (3); System.out.println (name+ "\t " +id+ "\t " +zip);*/}}catch  (sqlexception e)  { E.printstacktrace ();} FINALLY{//6 Close Resources    flashbacks off if (rs != null) {try {rs.close ();}  catch  (sqlexception e)  {e.printstacktrace ();}} if (stat != null) {try {stat.close ();}  catch  (sqlexception e)  {e.printstacktrace ();}} if (conn != null) {try {conn.close ();}  catch  (sqlexception e)  {e.printstacktrace ();}}}}

Attached: Executing DML statements     additions and deletions

import java.sql.connection;import java.sql.driver;import java.sql.drivermanager;import  java.sql.resultset;import java.sql.sqlexception;import java.sql.statement;public class  Jdbctest{public static void main (String[] args) {connection conn = null; statement  stat = null;int count = 0;try {driver driver =  new com.mysql.jdbc.driver ();D rivermanager.deregisterdriver (Driver); string url =  "JDBC:MYSQL://127.0.0.1:3306/JDBC"; string user =  "Root"; string password =  "123456"; Conn = drivermanager.getconnection (url, user,  password); stat = conn.createstatement ();//Execute SQL statement   :DML statement->insert update  delectstring sql_ins =  "Insert into t_user (name)  values  (' AAA ')"; count  = stat.executeupdate (Sql_ins); string sql_update =  "update t_user set name =  ' lll '   where id = 1 "; count =  stat.executeupdate (sql_update); string sql_del =  "delete from t_user where name =  ' aaa '"; count  = stat.executeupdate (Sql_del); System.out.println (count);}  catch  (sqlexception e)  {e.printstacktrace ();}}

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JDBC Six section-1