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Detailed explanation of JDBC function classes

2022-07-21 00:38:00 【Soup key】

Catalog
DriverManager Drive management objects
1. Registration drive
2. Get database connection
Connection Database connection object
1. Get the performer object
2. Manage affairs
3. Release resources
Statement perform sql Object of statement
1. perform DML sentence
2. perform DQL sentence
3. Release resources
ResultSet Result set object
1. Judge whether there is data in the result set
2. Get the data in the result set
3. Release resources
DriverManager Drive management objects
1. Registration drive
Register the given driver
static void registerDriver(Driver driver)
stay com.mysql.jdbc.Driver This static code block exists in the class
Static code blocks are used as classes are used
So you can register the operation of the driver
So write code to use ：
Class.forName("com.mysql.jdbc.Driver");
Be careful ：
We don't need to pass DriverManager Call static methods registerDriver(), Because as long as Driver Class is used , Will execute its static code block to complete the registration of the driver
MySQL5 After that, you can omit the steps of registering the driver , stay jar In bag , There is one. java.sql.Driver The configuration file , The document specifies com.mysql.jdbc.Driver
2. Get database connection
There is such a static method
static Connection getConnection(String url, String user, String password)
Return value ：Connection( Database connection object )
Parameters ：
url
Specify the path of the connection
grammar :jdbc:mysql://ip Address ( domain name ): Port number / Database name
user
user name
password
password
Connection Database connection object
1. Get the performer object
Get the normal performer object
Statement create Statement();
Get the precompiled performer object
PrepareStatement prepareStatement(String sql);
2. Manage affairs
Open transaction
setAutoCommit(Boolean autoCommit);
Parameter is false, Open transaction
Commit transaction
commit();
Roll back the transaction
rollback();
3. Release resources
Release the database connection object immediately
void close();
Statement perform sql Object of statement
1. perform DML sentence
int executeUpdate(String sql);
Return value ：
Returns the number of rows affected
2. perform DQL sentence
ResultSet executeQuery(String sql);
Return value ResultSet： Encapsulate the results of the query
Parameters sql： It can be executed select sentence
3. Release resources
Release the performer object immediately
void close();
ResultSet Result set object
1. Judge whether there is data in the result set
Boolean next();
There's data coming back true, And move the index down one line
No data returned false
2. Get the data in the result set
xxx getXxx(" Name ");
xxx Representative data type ( To get a column of data , The data type of this column )
for example ：
String getString("name");
int getInt("age");
3. Release resources
Release the result set object immediately ：
void close();