无涯教程可以通过实现ResultSetHandler接口或扩展ResultSetHandler的任何现有实现来创建自己的自定义处理程序。在下面给出的示例中通过扩展BeanHandler类创建了一个自定义处理程序EmployeeHandler。
以下是 Employee.java 的内容。
public class Employee { private int id; private int age; private String first; private String last; private String name; 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; } public String getName() { return name; } public void setName(String name) { this.name = name; } }
以下是 EmployeeHandler.java 文件的内容。
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import java.sql.ResultSet; import java.sql.SQLException; import org.apache.commons.dbutils.handlers.BeanHandler; public class EmployeeHandler extends BeanHandler<Employee> { public EmployeeHandler() { super(Employee.class); } @Override public Employee handle(ResultSet rs) throws SQLException { Employee employee = super.handle(rs); employee.setName(employee.getFirst() +", " + employee.getLast()); return employee; } }
以下是 MainApp.java 文件的内容。
import java.sql.Connection; import java.sql.DriverManager; import java.sql.SQLException; import org.apache.commons.dbutils.DbUtils; import org.apache.commons.dbutils.QueryRunner; import org.apache.commons.dbutils.ResultSetHandler; import org.apache.commons.dbutils.handlers.BeanHandler; public class MainApp { //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"; public static void main(String[] args) throws SQLException { Connection conn = null; QueryRunner queryRunner = new QueryRunner(); DbUtils.loadDriver(JDBC_DRIVER); conn = DriverManager.getConnection(DB_URL, USER, PASS); EmployeeHandler employeeHandler = new EmployeeHandler(); try { Employee emp = queryRunner.query(conn, "SELECT * FROM employees WHERE first=?", employeeHandler, "Sumit"); //显示对象信息 System.out.print("ID: " + emp.getId()); System.out.print(", Age: " + emp.getAge()); System.out.print(", Name: " + emp.getName()); } finally { DbUtils.close(conn); } } }
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: 28, Name: Sumit, Learnfk
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