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 { DbUtils.loadDriver(JDBC_DRIVER); QueryRunner run = new QueryRunner(CustomDataSource.getInstance()); ResultSetHandler<Employee> resultHandler = new BeanHandler<Employee>(Employee.class); Employee emp = queryRunner.query("SELECT * FROM employees WHERE id=?", resultHandler, 103); //显示对象信息 System.out.print("ID: " + emp.getId()); System.out.print(", Age: " + emp.getAge()); System.out.print(", First: " + emp.getFirst()); System.out.println(", Last: " + emp.getLast()); } }
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
参考链接
https://www.learnfk.com/dbutils/dbutils-using-datasource.html
标签:String,basicDataSource,数据源,无涯,QueryRunner,static,emp,DBUtils,public From: https://blog.51cto.com/u_14033984/7845548