无涯教程-DBUtils - 使用数据源到目前为止，无涯教程在使用QueryRunner时使用了连接对象，也可以无缝链

到目前为止，无涯教程在使用QueryRunner时使用了连接对象，也可以无缝链接数据源。下面的示例将演示如何在QueryRunner和数据源的帮助下使用Read查询读取记录。将从员工表中读取一条记录。

语法

QueryRunner queryRunner=new QueryRunner( dataSource );
Employee emp=queryRunner.query("SELECT * FROM employees WHERE first=?", resultHandler, "Sumit");

dataSource - 已配置数据源对象。
resultHandler - 将输出集映射到Employee对象的ResultSetHandler对象。
queryRunner - QueryRunner对象，用于从数据库读取员工对象。

以下是 Employee.java 的内容。

public class Employee {
   private int id;
   private int age;
   private String first;
   private String last;
   public int getId() {
      return id;
   }
   public void setId(int id) {
      this.id = id;
   }
   public int getAge() {
      return age;
   }
   public void setAge(int age) {
      this.age = age;
   }
   public String getFirst() {
      return first;
   }
   public void setFirst(String first) {
      this.first = first;
   }
   public String getLast() {
      return last;
   }
   public void setLast(String last) {
      this.last = last;
   }
}

以下是 CustomDatasource.java 的内容。

import javax.sql.DataSource;
import org.apache.commons.dbcp2.BasicDataSource;
public class CustomDataSource {
//JDBC 驱动程序名称和数据库 URL
static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";

static final String DB_URL = "jdbc:mysql://localhost:3306/emp";
//连接数据库凭据
static final String USER = "root";
static final String PASS = "admin";
private static DataSource datasource;
private static final BasicDataSource basicDataSource;
static {
basicDataSource = new BasicDataSource();
basicDataSource.setDriverClassName(JDBC_DRIVER);
basicDataSource.setUsername(USER);
basicDataSource.setPassword(PASS);
basicDataSource.setUrl(DB_URL);
}
public static DataSource getInstance() {
return basicDataSource;
}
}

以下是 MainApp.java 文件的内容。

import java.sql.SQLException;
import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.ResultSetHandler;
import org.apache.commons.dbutils.handlers.BeanHandler;
public class MainApp {
public static void main(String[] args) throws SQLException {
  </span><span class="typ">DbUtils</span><span class="pun">.</span><span class="pln">loadDriver</span><span class="pun">(</span><span class="pln">JDBC_DRIVER</span><span class="pun">);</span><span class="pln">
  </span><span class="typ">QueryRunner</span><span class="pln"> run </span><span class="pun">=</span><span class="pln"> </span><span class="kwd">new</span><span class="pln"> </span><span class="typ">QueryRunner</span><span class="pun">(</span><span class="typ">CustomDataSource</span><span class="pun">.</span><span class="pln">getInstance</span><span class="pun">());</span><span class="pln">
  </span><span class="typ">ResultSetHandler</span><span class="pun">&lt;</span><span class="typ">Employee</span><span class="pun">&gt;</span><span class="pln"> resultHandler </span><span class="pun">=</span><span class="pln"> </span><span class="kwd">new</span><span class="pln"> </span><span class="typ">BeanHandler</span><span class="pun">&lt;</span><span class="typ">Employee</span><span class="pun">&gt;(</span><span class="typ">Employee</span><span class="pun">.</span><span class="kwd">class</span><span class="pun">);</span><span class="pln">

  </span><span class="typ">Employee</span><span class="pln"> emp </span><span class="pun">=</span><span class="pln"> queryRunner</span><span class="pun">.</span><span class="pln">query</span><span class="pun">(</span><span class="str">"SELECT * FROM employees WHERE id=?"</span><span class="pun">,</span><span class="pln">
     resultHandler</span><span class="pun">,</span><span class="pln"> </span><span class="lit">103</span><span class="pun">);</span><span class="pln">
  
  </span><span class="com">//显示对象信息</span><span class="pln">
  </span><span class="typ">System</span><span class="pun">.</span><span class="kwd">out</span><span class="pun">.</span><span class="kwd">print</span><span class="pun">(</span><span class="str">"ID: "</span><span class="pln"> </span><span class="pun">+</span><span class="pln"> emp</span><span class="pun">.</span><span class="pln">getId</span><span class="pun">());</span><span class="pln">
  </span><span class="typ">System</span><span class="pun">.</span><span class="kwd">out</span><span class="pun">.</span><span class="kwd">print</span><span class="pun">(</span><span class="str">", Age: "</span><span class="pln"> </span><span class="pun">+</span><span class="pln"> emp</span><span class="pun">.</span><span class="pln">getAge</span><span class="pun">());</span><span class="pln">
  </span><span class="typ">System</span><span class="pun">.</span><span class="kwd">out</span><span class="pun">.</span><span class="kwd">print</span><span class="pun">(</span><span class="str">", First: "</span><span class="pln"> </span><span class="pun">+</span><span class="pln"> emp</span><span class="pun">.</span><span class="pln">getFirst</span><span class="pun">());</span><span class="pln">
  </span><span class="typ">System</span><span class="pun">.</span><span class="kwd">out</span><span class="pun">.</span><span class="pln">println</span><span class="pun">(</span><span class="str">", Last: "</span><span class="pln"> </span><span class="pun">+</span><span class="pln"> emp</span><span class="pun">.</span><span class="pln">getLast</span><span class="pun">());</span><span class="pln">

}
}

创建完源文件后，让无涯教程运行该应用程序。如果您的应用程序一切正常，它将打印以下消息。

ID: 103, Age: 33, First: Sumit, Last: Learnfk

无涯教程-DBUtils - 使用数据源

语法

参考链接