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JDBC exercises
2022-06-12 00:33:00 【DanielMaster】
Programming is right for dept Table implements the following operations
- Set up the project correctly and finish reading the external property file
- Paging display dept Table data information , Each page is displayed 2 strip , And encapsulate the data into Dept Collection .( The parameters are the number of entries per page and the displayed page number )
- towards dept Insert in table "50",“DEVELOPMENT”,“JAP”（ Parameter is dept object ）
- Delete dept In the table 50 Information of department No ( Parameter is deptno)
Departmental table
package practice;
/**
*
* @author Yang
* Departmental table
*/
public class Dept {
private int deptno;
private String dname;
private String loc;
public Dept() {
}
public Dept(int deptno, String dname, String loc) {
super();
this.deptno = deptno;
this.dname = dname;
this.loc = loc;
}
public int getDeptno() {
return deptno;
}
public void setDeptno(int deptno) {
this.deptno = deptno;
}
public String getDname() {
return dname;
}
public void setDname(String dname) {
this.dname = dname;
}
public String getLoc() {
return loc;
}
public void setLoc(String loc) {
this.loc = loc;
}
@Override
public String toString() {
return "Dept [deptno=" + deptno + ", dname=" + dname + ", loc=" + loc + "]";
}
}
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JdbcUtils class
package practice;
import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Properties;
/** Reading of external property file
* Connection acquisition and resource release
* Solve hard coding problem
*/
public class JdbcUtils {
// It is written in a static code block so that each time a class is loaded , Get the connection before creating the instance , It only takes one time
static String url = null;
static String user = null;
static String password = null;
static {
try {
// With the help of Properties class , Then create an input stream , Use reflection to get the contents
Properties pros = new Properties();
//getResourceAsStream Is load .class In the document jdbc file
InputStream is = JdbcUtils.class.getClassLoader().getResourceAsStream("jdbc.properties");
// Load mapping pairs
pros.load(is);
is.close();
// obtain value value
url = pros.getProperty("url");
user = pros.getProperty("user");
password = pros.getProperty("password");
// Register once
Class.forName(pros.getProperty("driver"));
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
// Get the connection , Before getting a connection , The configuration file has been created
public static Connection getConnection() {
try {
return DriverManager.getConnection(url, user, password);
} catch (SQLException e) {
throw new RuntimeException(" Failed to get connection ");
}
}
// Release resources
public static void close(Connection conn, PreparedStatement ps, ResultSet rs) {
try {
if (rs != null) {
rs.close();
}
if (ps != null) {
ps.close();
}
if (conn != null) {
conn.close();
}
} catch (SQLException e) {
e.printStackTrace();
}
}
}
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jdbc.properties file
- stay src Right click New -> File, stay File name In the input jdbc.properties that will do , And then type in the content
driver=com.mysql.jdbc.Driver
url=jdbc:mysql:///bd1906?useSSL=true
user=root
password=root
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TestDept Test class
package practice;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
public class TestDept {
public static void main(String[] args) {
// Pagination 、 Insert 、 Delete
System.out.println(queryAll(1, 2));
System.out.println(queryAll(2, 2));
// System.out.println(insert(new Dept(50,"DEVELOPMENT","JAP")));
// System.out.println(delete(50));
}
// According to the title requirements, the number of incoming pages and the number displayed on each page
public static List<Dept> queryAll(int page, int num) {
List<Dept> list = new ArrayList<Dept>();
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
try {
// Call our own class
conn = JdbcUtils.getConnection();
// Paging query in sql Add... In the sentence limit Limit the number of pages
String sql = "select * from dept limit ?,?";
ps = conn.prepareStatement(sql);
// We want to make sure that the first page is (0,2) From 0( It doesn't contain ) Start , Count back two , That is 1,2, The same is true for the second page
ps.setInt(1, (page - 1) * num);
ps.setInt(2, num);
rs = ps.executeQuery();
// obtain
while (rs.next()) {
int deptno = rs.getInt("deptno");
String dname = rs.getString("dname");
String loc = rs.getString("loc");
Dept dept = new Dept(deptno, dname, loc);
list.add(dept);
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
JdbcUtils.close(conn, ps, rs);
}
return list;
}
public static int insert(Dept dept) {
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
int rows = 0;
try {
conn = JdbcUtils.getConnection();
String sql = "insert into dept values(?,?,?)";
ps = conn.prepareStatement(sql);
ps.setInt(1, dept.getDeptno());
ps.setString(2, dept.getDname());
ps.setString(3, dept.getLoc());
rows = ps.executeUpdate();
} catch (SQLException e) {
e.printStackTrace();
} finally {
JdbcUtils.close(conn, ps, rs);
}
return rows;
}
public static int delete(int id) {
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
int rows = 0;
try {
conn = JdbcUtils.getConnection();
String sql = "delete from dept where deptno =?";
ps = conn.prepareStatement(sql);
ps.setInt(1, id);
rows = ps.executeUpdate();
} catch (SQLException e) {
e.printStackTrace();
} finally {
JdbcUtils.close(conn, ps, rs);
}
return rows;
}
}
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Inserted and deleted annotation references
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