Detailed explanation of JDBC connection to MySQL instance_MySQL

JDBC connects to MySQL

JDBC connects to MySQL

Load and register JDBC driver

Class.forName("com.mysql.jdbc.Driver");
Class.forName("com.mysql.jdbc.Driver").newInstance();

JDBC URL defines the connection between driver and data source

Standard syntax:

d10d500e8bec722476599c70ebc64c7f:2f760b855a77c9af4717b4b4aa44aebc:d7443e16a772550631d9755738121cfd

MySQL JDBC URL format:

jdbc:mysql//[hostname][:port]/[dbname][?param1=value1][¶m2=value2]….

Example: jdbc:mysql://localhost:3306/sample_db?user=root&password=your_password

Common parameters:
user Username
password                                                           autoReconnect Connection failed, whether to reconnect (true/false)
maxReconnect The number of attempts to reconnect
initialTimeout The interval between trying to reconnect
maxRows Returns the maximum number of rows
useUnicode Whether to use Unicode font encoding (true/false)
characterEncoding What encoding (GB2312/UTF-8/…)
relaxAutocommit Whether to submit automatically (true/false)
capitalizeTypeNames The names of data definitions are expressed in uppercase letters

Create connection object

String url="jdbc:mysql://localhost:3306/sample_db?user=root&password=your_password"; Connection con = DriverManager.getConnection(url);

Create SQL Statement Object

Statement stmt = con.createStatement();

Execute SQL statements

executeQuery()
String query = "select * from test";
ResultSet rs=stmt.executeQuery(query);
结果集ResultSet
while(rs.next())
{rs.getString(1);rs.getInt(2);}
executeUpdate()
String upd="insert into test (id,name) values(1001,xuzhaori)";
int con=stmt.executeUpdate(upd);
execute()

Example:

try
{
 }
catch(SQLException sqle)
{
}
finally
{
}

Java Types and SQL Types Technical Manual P421

PreparedStatement

PreparedStatement stmt = conn.prepareStatement("insert into test(id,name)values(?,?)");

stmt.setInt(1,id);
stmt.setString(2,name);

Note: Once the parameter value of a statement is set, the modified statement can be executed multiple times until it is cleared by calling the clearParameters() method

CallableStatement (pre-stored program) technical manual P430

JDBC2.0 use

The cursor in the ResultSet object moves freely up and down

Statement stmt = con.createStatement (ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.CONCUR_READ_ONLY);
ResultSet rs=stmt.executeQuery("select * from test");

public Statement createStatement(int resultSetType,int resultSetConcuttency) throws SQLException

resultSetType

TYPE_FORWARD_ONLY Only the next() method can be used.

TYPE_SCROLL_SENSITIVE can be moved up and down and the changed value can be obtained.
TYPE_SCROLL_INSENSITIVE can move up and down.

resultSetConcuttency

CONCUR_READ_ONLY Read only

CONCUR_UPDATABLE The ResultSet object can perform database additions, modifications, and removals

Directly use the ResultSet object to update data

New data

Statement stmt＝con.createStatement（ResultSet.TYPE_SCROLL_SENSITIVE,ResultSet.CONCUR_PUDATABLE）;
ResultSet uprs=stmt.executeQuery("select * from test");
uprs.moveToInsertRow();
uprs.updateInt(1,1001);
uprs.updateString(2,"许召日");
uprs.insertRow;

Update data

Statement stmt＝con.createStatement（ResultSet.TYPE_SCROLL_SENSITIVE,ResultSet.CONCUR_PUDATABLE）;
ResultSet uprs=stmt.executeQuery("select * from test");
uprs.last();
uprs.updateString("name","xuzhaori");
uprs.updateRow;

Delete data

Statement stmt＝con.createStatement（ResultSet.TYPE_SCROLL_SENSITIVE,ResultSet.CONCUR_PUDATABLE）;
ResultSet uprs=stmt.executeQuery("select * from test");
uprs.absolute(4);
uprs.deleteRow();

Batch processing

con.setAutoCommit(false); 关闭自动认可模式
Statement stmt=con.createStatement();
int[] rows;
stmt.addBatch("insert into test values(1001,xuzhaori)");
stmt.addBatch("insert into test values(1002,xuyalin)");
rows=stmt.executeBatch();
con.commit(); 没有任何错误，执行批处理stmt.executeBatch();

JNDI-Data Source and Connection Pool

Tomcat’s JDBC data source settings technical manual P439

Connection Pooling Tool-Proxool Var 0.8.3 Technical Manual P446

Set web.xml

<&#63;xml version="1.0" encoding="ISO-8859-1"&#63;>
<!--<&#63;xml version="1.0" encoding="GB2312"&#63;>-->
 
<web-app xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"
version="2.4">
….
<servlet>
<servlet-name>ServletConfigurator</servlet-name>
<servlet-class>org.logicalcobwebs.proxool.configuration.ServletConfigurator</servlet-class>
 
<init-param>
<param-name>propertyFile</param-name>
<param-value>WEB-INF/classes/Proxool.properties</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
后端统计端口添加下列
<servlet>
<servlet-name>Admin</servlet-name>
<servlet-class>org.logicalcobwebs.proxool.admin.servlet.AdminServlet</servlet-class>
</servlet>
 
<servlet-mapping>
<servlet-name>Admin</servlet-name>
<url-pattern>/Admin</url-pattern>
</servlet-mapping>
 
….
 
</web-app>

Configure Proxool.properties

jdbc-0.proxool.alias=JSPBook
jdbc-0.proxool.driver-class=com.mysql.jdbc.Driver
jdbc-0.proxool.driver-url=jdbc:mysql://localhost:3306/sample_db?user=root&password=browser&useUnicode=true&characterEncoding=UTF-8
jdbc-0.proxool.maximum-connection-count=10
jdbc-0.proxool.prototype-count=4
jdbc-0.proxool.house-keeping-test-sql=select CURRENT_DATE
jdbc-0.proxool.verbose=true
jdbc-0.proxool.statistics=10s,1m,1d  后端统计接口添加此行
jdbc-0.proxool.statistics-log-level=DEBUG

Use Proxool connection pool

Connection con = DriverManager.getConnection("proxool.JSPBook");
Statement stmt = con.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.CONCUR_UPDATABLE);
String query = "SELECT * FROM employee";
ResultSet rs = stmt.executeQuery(query);

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