Java 程序使用列的方法获取 JDBC 的列名
原文:https://www . geesforgeks . org/Java-程序使用方法-列获取列名-在 jdbc 中/
Java 数据库连接或 JDBC 是一个 Java API(应用程序编程接口)，用于通过 Java 应用程序执行数据库操作。它允许通过 Java 应用程序执行用于创建表和数据操作的 SQL 命令。Java 支持 java.sql 包，该包包含用于访问和处理存储在数据库中的数据的内置方法。java.sql 中的方法抛出 sql 异常，因此代码块必须放在 try 块中，如果有任何异常，则让 catch 块处理异常。
程序:
- for name () is a static class method for loading drivers.
- Next, use the [*getconnection ()* method of the DriverManager class to establish a connection to the database. getConnection() Accept the URL, user name and password to establish a connection. The methods defined in the statement are used to interact with the database.
- Create a table first, and then insert records into the table.
- SQL commands are batched together with addbatch () , and executed at one time with Execute batch () method.
- The records in the table are extracted into the result set.
- The getmetadata () method of the ResultSet is used to obtain the metadata of the records extracted into the ResultSet.
- The getcolumncount () and getcolumnname () methods of the resultset metadata interface are used to obtain the number of columns in the table and the name of each column.
例 1:
爪哇
// Java Program to Use Methods of Column
// to get column name in JDBC
// Step 1: Importing DB files
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.Statement;
// Class to get columns
public class GFG {
// Main driver method
public static void main(String args[])
{
try {
// Step 2: Loading and registering drivers
// Loading driver class
// using forName() method
Class.forName("oracle.jdbc.OracleDriver");
// Step 3: Establishing te connection
Connection con = DriverManager.getConnection(
"jdbc:oracle:thin:@localhost:1521:xe",
"username", "password");
Statement s = con.createStatement();
// Step 4: Create a statement
String sql1
= "CREATE TABLE ACADEMY(COURSE_ID VARCHAR2(20) PRIMARY KEY, COURSE_NAME VARCHAR2(20),MENTOR VARCHAR2(20),COURSE_FEE NUMBER)";
// Step 5: Process the query
// Inserting records in the table
String sql2
= "INSERT INTO ACADEMY VALUES('C101','MATH','ROBERT',5000)";
String sql3
= "INSERT INTO ACADEMY VALUES('C102','PHYSICS','JANE',8000)";
String sql4
= "INSERT INTO ACADEMY VALUES('C103','HISTORY','ADAM',6000)";
String sql5
= "INSERT INTO ACADEMY VALUES('C104','BIOLOGY','MARIE',5000)";
String sql6
= "INSERT INTO ACADEMY VALUES('C105','ENGLISH','ALBERT',3000)";
s.addBatch(sql1);
s.addBatch(sql2);
s.addBatch(sql3);
s.addBatch(sql4);
s.addBatch(sql5);
s.addBatch(sql6);
// Step 6: Execute the statements
// executing the sql commands
s.executeBatch();
// Obtaining the resultset
ResultSet rs
= s.executeQuery("SELECT * FROM ACADEMY");
while (rs.next()) {
System.out.println(
rs.getString(1) + "\t\t"
+ rs.getString(2) + "\t\t"
+ rs.getString(3) + "\t\t"
+ rs.getString(4));
}
// Retrieving the ResultSetMetadata object
ResultSetMetaData rsMetaData = rs.getMetaData();
System.out.println(
"List of column names in the current table: ");
// Retrieving the list of column names
int count = rsMetaData.getColumnCount();
for (int i = 1; i& lt; = count; i++) {
System.out.print(rsMetaData.getColumnName(i)
+ "\t");
}
// Step 7: Close the connection
con.commit();
con.close();
}
// Catch block to handle exceptions
catch (Exception e) {
// Print the exception
System.out.println(e);
}
}
}
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