Explanation of JDBC classes

JDBC Operation steps of :
    1) Registration drive
            java.sql.DriverManager: Driver management ( Manage a group of JDBC Service )
             Registration driven method :
        public static void registerDriver(Driver driver):
             Formal parameter passing It's the interface , You need to change the sub implementation class object of the interface
            
             Drive provided Jar package :com.mysql.jdbc.Driver  implements  java.sql.Driver Interface
            
             Normal format : ( disadvantages : It's equivalent to registering twice )
            Driver driver = new  com.mysql.jdbc.Driver() ;
//            DriverManager.registerDriver(driver);
     Bottom source :
         Package name :com.mysql.jdbc
        public class Driver  implements java.sql.Driver {
        
             Static code block : Load the Driver Class , Statically related code is executed first !
            static {
                try {
                        // Use the driver management to register the driver
                    java.sql.DriverManager.registerDriver(new Driver());
                  } catch (SQLException E) {
                throw new RuntimeException("Can't register driver!");
            }
                }
            
        
            }
            
            
             After the optimization : Using the idea of reflection : Just load com.mysql.jdbc.Driver This class is ok !
            Class.forName("com.mysql.jdbc.Driver") ;// Ensure the downward compatibility of versions , It is suggested to always give this sentence !
            
            
            
    2) Drive management DriverManager Get the connection object of the database :Connection(java.sql)
    Drive management DriverManger : Manage a group of JDBC Service
    
            public static Connection getConnection(
            String url,String user,String password): Get the connection
            
    url: Uniform resource locator : Namely uri A subset of
             Use url： 
                jdbc:mysql:// domain name : Port number / Database name ( The library must exist !)
                
                 There are a lot of agreements :
                    ftp://
                    http:// domain name : Port number / Specific request address for access
                    mail: Email protocol
                    thunder:// Thunder Association ...
                    file:// Local file protocol
                    
                    ...
    uri: Network resources are a general term ！
    
            http://localhost:8080/login  :URL
            
            /login: uri
            
            
    user: user name : The name of the user connecting to the database :root
    password: The password used to connect to the database
    
    3)Connection: Connection object java.sql.Connection
     Represents a session with a database ( Connect ), You can get the metadata information of the current linked database ( The structure of the table / The field type of the table ..)
         Member method :
                Statement createStatement(): establish Statement Perform object
                   And will specify sql Send to the specified database
                   
                PreparedStatement prepareStatement(String sql): The parameter sql Statement to execute
                 Send to database , And get the precompiled object
                
                DatabaseMetaData getMetaData(): Get metadata information related to the database
                 It includes the structure of some databases and tables ....
                
                
                
    4)Statement:java.sql.Statement 
     Perform object
             Execute static sql sentence
             give an example :
            "update account set balance = balance + 500 where id = 1;
            id Value , to balance+500 Value ,( Hard encoding )
            
         Member method :
                int executeUpdate(String sql): Common methods
                 in the light of DML sentence :insert,update,delete, With returned results
                 Can perform the most basic DDL sentence , There is no content returned !
                
                ResultSet executeQuery(String sql): Special execution DQL sentence :select..
                 The result returned : Result set object ( Data table of database result set )
                
    
    
    5)PreparedStatement Perform object ( Precompiled objects )  extends Statement
             precompiled SQL Object of statement . 
                 Give parameterized sql Assign a value
                sql:
                    insert into Table name (name,age,gender) values(?,?,?) ; Placeholder
                publi void setXXX( The first parameter , actual value ) ;
                
                ResultSet executeQuery(): perform DQL sentence  
                int executeUpdate(): perform DML Statement will return the result : Affected the number of rows
                                     Appoint DDL sentence , The return is 0
                
            
            
            
    6)ResultSet: The data table of the result set generated after the query (java.sql.xx)