具有數(shù)據(jù)庫管理員權(quán)限，以在給定模式中數(shù)據(jù)庫表中查詢數(shù)據(jù)記錄。要執(zhí)行以下示例，需要用實(shí)際用戶名和密碼替換這里用戶名(username)和密碼(password)。
MySQL或數(shù)據(jù)庫已啟動并運(yùn)行。

所需步驟

使用JDBC應(yīng)用程序向表中查詢數(shù)據(jù)記錄需要以下步驟：

導(dǎo)入包：需要包含包含數(shù)據(jù)庫編程所需的JDBC類的包。大多數(shù)情況下，使用import java.sql.*就足夠了。
注冊JDBC驅(qū)動程序：需要初始化驅(qū)動程序，以便可以程序中打開數(shù)據(jù)庫的通信通道。
打開連接：需要使用DriverManager.getConnection()方法來創(chuàng)建一個Connection對象，它表示與數(shù)據(jù)庫服務(wù)器的物理連接。
執(zhí)行查詢：需要使用類型為Statement的對象來構(gòu)建和提交SQL語句，以在選擇的數(shù)據(jù)庫的表中查詢數(shù)據(jù)記錄。
提取數(shù)據(jù)：執(zhí)行SQL查詢后，可以從表中獲取記錄。
清理環(huán)境：需要明確地關(guān)閉所有數(shù)據(jù)庫資源，而不依賴于JVM的垃圾收集。

示例代碼

復(fù)制以下示例代碼保存到文件：SelectRecords.java中，然后編譯并運(yùn)行如下 -

//STEP 1. Import required packages
import java.sql.*;

public class SelectRecords {
   // JDBC driver name and database URL
   static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";  
   static final String DB_URL = "jdbc:mysql://localhost/jdbc_db";

   //  Database credentials
   static final String USER = "root";
   static final String PASS = "123456";

   public static void main(String[] args) {
   Connection conn = null;
   Statement stmt = null;
   try{
      //STEP 2: Register JDBC driver
      Class.forName("com.mysql.jdbc.Driver");

      //STEP 3: Open a connection
      System.out.println("Connecting to a selected database...");
      conn = DriverManager.getConnection(DB_URL, USER, PASS);
      System.out.println("Connected database successfully...");

      //STEP 4: Execute a query
      System.out.println("Creating statement...");
      stmt = conn.createStatement();

      String sql = "SELECT id, first, last, age FROM student";
      ResultSet rs = stmt.executeQuery(sql);
      //STEP 5: Extract data from result set
      while(rs.next()){
         //Retrieve by column name
         int id  = rs.getInt("id");
         int age = rs.getInt("age");
         String first = rs.getString("first");
         String last = rs.getString("last");

         //Display values
         System.out.print("ID: " + id);
         System.out.print(", Age: " + age);
         System.out.print(", First: " + first);
         System.out.println(", Last: " + last);
      }
      rs.close();
   }catch(SQLException se){
      //Handle errors for JDBC
      se.printStackTrace();
   }catch(Exception e){
      //Handle errors for Class.forName
      e.printStackTrace();
   }finally{
      //finally block used to close resources
      try{
         if(stmt!=null)
            conn.close();
      }catch(SQLException se){
      }// do nothing
      try{
         if(conn!=null)
            conn.close();
      }catch(SQLException se){
         se.printStackTrace();
      }//end finally try
   }//end try
   System.out.println("Goodbye!");
}//end main
}//end JDBCExample

編譯上面代碼，如下 -

F:\worksp\jdbc> javac -Djava.ext.dirs=F:\worksp\jdbc\libs SelectRecords.java

執(zhí)行上面代碼，如下 -

## 可先創(chuàng)建表或插入數(shù)據(jù) -
## F:\worksp\jdbc> java -Djava.ext.dirs=F:\worksp\jdbc\libs InsertRecords

F:\worksp\jdbc>java -Djava.ext.dirs=F:\worksp\jdbc\libs SelectRecords
Connecting to a selected database...
Thu Jun 01 23:11:55 CST 2017 WARN: Establishing SSL connection without server's identity verification is not recommended. According to MySQL 5.5.45+, 5.6.26+ and 5.7.6+ requirements SSL connection must be established by default if explicit option isn't set. For compliance with existing applications not using SSL the verifyServerCertificate property is set to 'false'. You need either to explicitly disable SSL by setting useSSL=false, or set useSSL=true and provide truststore for server certificate verification.
Connected database successfully...
Creating statement...
ID: 100, Age: 18, First: C++, Last: Li
ID: 101, Age: 25, First: Python, Last: Py
ID: 102, Age: 30, First: Ruby, Last: Ru
ID: 103, Age: 28, First: Java, Last: Ja
Goodbye!

F:\worksp\jdbc>

下一篇：JDBC刪除數(shù)據(jù)實(shí)例