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Java的JDBC中Statement与CallableStatement对象实例

转载 作者：qq735679552 更新时间：2022-09-29 22:32:09 25 4
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这篇CFSDN的博客文章Java的JDBC中Statement与CallableStatement对象实例由作者收集整理，如果你对这篇文章有兴趣，记得点赞哟.

JDBC Statement对象实例 以下是利用以下三种查询以及打开和关闭说明的例子:

boolean execute(String SQL) : 返回一个布尔值true，如果ResultSet对象可以被检索，否则返回false。使用这个方法来执行SQL DDL语句，或当需要使用真正的动态SQL.

int executeUpdate(String SQL) : 返回受影响的SQL语句执行的行数。使用此方法来执行，而希望得到一些受影响的行的SQL语句 - 例如，INSERT，UPDATE或DELETE语句.

ResultSet executeQuery(String SQL) : 返回ResultSet对象。当希望得到一个结果集使用此方法，就像使用一个SELECT语句.

基于对环境和数据库安装在前面的章节中做此示例代码已被写入.

复制下面的例子中JDBCExample.java，编译并运行，如下所示:

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//STEP 1. Import required packages
import java.sql.*;
 
public class JDBCExample {
   // JDBC driver name and database URL
   static final String JDBC_DRIVER = "com.mysql.jdbc.Driver" ;
   static final String DB_URL = "jdbc:mysql://localhost/EMP" ;
 
   // Database credentials
   static final String USER = "username" ;
   static final String PASS = "password" ;
  
   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 database..." );
    conn = DriverManager.getConnection(DB_URL,USER,PASS);
 
    //STEP 4: Execute a query
    System.out.println( "Creating statement..." );
    stmt = conn.createStatement();
    String sql = "UPDATE Employees set age=30 WHERE id=103" ;
   
    // Let us check if it returns a true Result Set or not.
    Boolean ret = stmt.execute(sql);
    System.out.println( "Return value is : " + ret.toString() );
 
    // Let us update age of the record with ID = 103;
    int rows = stmt.executeUpdate(sql);
    System.out.println( "Rows impacted : " + rows );
 
    // Let us select all the records and display them.
    sql = "SELECT id, first, last, age FROM Employees" ;
    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);
    }
    //STEP 6: Clean-up environment
    rs.close();
    stmt.close();
    conn.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 )
       stmt.close();
    } catch (SQLException se2){
    } // nothing we can do
    try {
      if (conn!= null )
       conn.close();
    } catch (SQLException se){
      se.printStackTrace();
    } //end finally try
   } //end try
   System.out.println( "Goodbye!" );
} //end main
} //end JDBCExample

现在编译上面的例子如下:

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C:>javac JDBCExample.java

当运行JDBCExample，它会产生以下结果:

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C:>java JDBCExample
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Connecting to database...
Creating statement...
Return value is : false
Rows impacted : 1
ID: 100, Age: 18, First: Zara, Last: Ali
ID: 101, Age: 25, First: Mahnaz, Last: Fatma
ID: 102, Age: 30, First: Zaid, Last: Khan
ID: 103, Age: 30, First: Sumit, Last: Mittal
Goodbye!

JDBC CallableStatement对象实例 下面是利用CallableStatement连同下列getEmpName()的MySQL存储过程的例子:

请确定已经在EMP数据库中创建该存储过程。可以使用MySQL查询浏览器来完成它.

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DELIMITER $$
 
DROP PROCEDURE IF EXISTS `EMP`.`getEmpName` $$
CREATE PROCEDURE `EMP`.`getEmpName`
   ( IN EMP_ID INT , OUT EMP_FIRST VARCHAR (255))
BEGIN
   SELECT first INTO EMP_FIRST
   FROM Employees
   WHERE ID = EMP_ID;
END $$
 
DELIMITER ;

基于对环境和数据库安装在前面的章节中进行，这个范例程式码已被写入.

复制下面的例子中JDBCExample.java，编译并运行，如下所示:

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//STEP 1. Import required packages
import java.sql.*;
 
public class JDBCExample {
   // JDBC driver name and database URL
   static final String JDBC_DRIVER = "com.mysql.jdbc.Driver" ;
   static final String DB_URL = "jdbc:mysql://localhost/EMP" ;
 
   // Database credentials
   static final String USER = "username" ;
   static final String PASS = "password" ;
  
   public static void main(String[] args) {
   Connection conn = null ;
   CallableStatement stmt = null ;
   try {
    //STEP 2: Register JDBC driver
    Class.forName( "com.mysql.jdbc.Driver" );
 
    //STEP 3: Open a connection
    System.out.println( "Connecting to database..." );
    conn = DriverManager.getConnection(DB_URL,USER,PASS);
 
    //STEP 4: Execute a query
    System.out.println( "Creating statement..." );
    String sql = "{call getEmpName (?, ?)}" ;
    stmt = conn.prepareCall(sql);
   
    //Bind IN parameter first, then bind OUT parameter
    int empID = 102 ;
    stmt.setInt( 1 , empID); // This would set ID as 102
    // Because second parameter is OUT so register it
    stmt.registerOutParameter( 2 , java.sql.Types.VARCHAR);
   
    //Use execute method to run stored procedure.
    System.out.println( "Executing stored procedure..." );
    stmt.execute();
 
    //Retrieve employee name with getXXX method
    String empName = stmt.getString( 2 );
    System.out.println( "Emp Name with ID:" +
         empID + " is " + empName);
    stmt.close();
    conn.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 )
       stmt.close();
    } catch (SQLException se2){
    } // nothing we can do
    try {
      if (conn!= null )
       conn.close();
    } catch (SQLException se){
      se.printStackTrace();
    } //end finally try
   } //end try
   System.out.println( "Goodbye!" );
} //end main
} //end JDBCExample

现在编译上面的例子如下:

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C:>javac JDBCExample.java

当运行JDBCExample，它会产生以下结果:

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C:>java JDBCExample
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Connecting to database...
Creating statement...
Executing stored procedure...
Emp Name with ID:102 is Zaid
Goodbye!

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