下面是组件中DbUtils类和BeanListHandler类的详细用法的例子:

GuestBook.java源文件

package com.gdufs.xxy;

public class GuestBook {
private Integer id;
private String name;

public IntegergetId() {
return id;
}

public StringgetName() {
return name;
}

public voidsetId(Integer id) {
this.id = id;
}

public voidsetName(String name) {
this.name = name;
}
}

BeanListExample.java类文件

packagecom.gdufs.xxy;

importorg.apache.commons.dbutils.DbUtils;
import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanListHandler;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.List;

public class BeanListExample {

public staticvoid main(String[] args) {
Connection conn = null;
String url = "jdbc:mysql://localhost:3306/test";
String driver = "com.mysql.jdbc.Driver";
String user = "root";
String password = "520134";

DbUtils.load(driver);

try {
conn = DriverManager.getConnection(url,user,password);
QueryRunner qr = new QueryRunner();
List results = (List)qr.query(conn,"select id,name fromguestbook",new BeanListHandler(GuestBook.class));
for(int i=0;i<results.size(); i++) {
GuestBook gb = (GuestBook)results.get(i);
System.out.println("id:"+gb.getId()+";name:"+gb.getName());
}
}
catch(SQLException e) {
e.printStackTrace();
} finally {
DbUtils.closeQuietly(conn);
}
}
}

importorg.apache.commons.dbutils.DbUtils;   
 importorg.apache.commons.dbutils.QueryRunner;  
 importorg.apache.commons.dbutils.handlers.MapListHandler;   
   
 import java.sql.Connection;   
 import java.sql.DriverManager;   
 import java.sql.SQLException;   
   
 import java.util.Map;   
 import java.util.List;   
   
 public class DbUtilsUseMapMySQL {   
   public static void main(String[] args){   
     Connection conn = null;   
     String jdbcURL = "jdbc:mysql://localhost/octopus";   
     String jdbcDriver ="com.mysql.jdbc.Driver";   
     String user = "root";   
     String password ="root";   
   
     try {   
      DbUtils.loadDriver(jdbcDriver);   
       conn =DriverManager.getConnection(jdbcURL, user, password);   
   
       QueryRunner qRunner = newQueryRunner();   
   
       List mapList = (List)qRunner.query(conn, "select id, name from animals_table",   
           new MapListHandler());   
   
       for (int i = 0; i <mapList.size(); i++) {   
         Map map = (Map)mapList.get(i);   
        System.out.println("id=" + map.get("id"));   
        System.out.println("name=" + map.get("name"));   
        System.out.println("—————–");  
       }  
   
       System.out.println("DbUtils_UseMap_MySQL:end.");   
   
     } catch (SQLException e) {   
       // handle the exception   
       e.printStackTrace();   
     } finally {   
       DbUtils.closeQuietly(conn);   
     }  
   }  
 }  
   
 class Employee {   
   private int id;   
   private String name;   
   public Employee() {   
   }  
   public void setName(String name){   
     this.name = name;   
   }  
   public String getName() {   
     return this.name;   
   }  
   
   public void setId(int id) {   
     this.id = id;   
   }  
   
   public int getId() {   
     return this.id;   
   }  
   
   public void print() {   
     System.out.println("id=" +id + " name=" + name);   
   }  
 }

1.DAO基类(数据库操作基类)
 
这里使用了层超类模式，复用代码，统一处理异常，日志等等..
 
BaseDAO:
 
package com.d1zhan;
 
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.List;
 
import org.apache.commons.dbutils.DbUtils;
import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanListHandler;

public classBaseDAO {
    /**
     * 获取数据库连接
     * @return
     */
    public Connection getConnection() {
        Connection conn = null;
        String jdbcURL ="jdbc:mysql://localhost/dbname";
        String jdbcDriver ="com.mysql.jdbc.Driver";
        String user = "root";
        String password = "root";
        try {
           DbUtils.loadDriver(jdbcDriver);
            conn =DriverManager.getConnection(jdbcURL, user, password);
        } catch (SQLException e) {
            // handle the exception
            e.printStackTrace();
        } finally {
            DbUtils.closeQuietly(conn);
        }
        return conn;
    }
 
    /**
    * 查找多个对象
     * @param sqlString
     * @param clazz
     * @return
     */
    public List query(String sqlString,Class clazz) {
        List beans = null;
        Connection conn = null;
        try {
            conn = getConnection();
            QueryRunner qRunner = new QueryRunner();
            beans =
                (List) qRunner.query(
                    conn,
                    sqlString,
                    newBeanListHandler(clazz));
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            DbUtils.closeQuietly(conn);
        }
        return beans;
    }
 
    /**
     * 查找对象
     * @param sqlString
     * @param clazz
     * @return
     */
    public Object get(String sqlString,Class clazz) {
        List beans = null;
        Object obj = null;
        Connection conn = null;
        try {
            conn = getConnection();
            QueryRunner qRunner = new QueryRunner();
            beans =
                (List) qRunner.query(
                    conn,
                    sqlString,
                    newBeanListHandler(clazz));
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            DbUtils.closeQuietly(conn);
        }
        if(beans!=null &&!beans.isEmpty()){ //注意这里
             obj=beans.get(0);

}

return obj;
    }
 
    /**
     * 执行更新的sql语句,插入,修改,删除
     * @param sqlString
     * @return
     */
    public boolean update(StringsqlString) {
        Connection conn = null;
        boolean flag = false;
        try {
            conn = getConnection();
            QueryRunner qRunner = new QueryRunner();
            int i =qRunner.update(conn,sqlString);
            if (i > 0) {
                flag = true;
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            DbUtils.closeQuietly(conn);
        }
        return flag;
    }
}
 
 commons-DBUtils实践

1,Employee 雇员数据库操作DAO类
 
 
大家可以看到，下面的DAO类，继承BaseDAO,方法体都是组装sql语句，不必关心异常的处理，资源的管理(Connection,Statement等)，这样代码简洁，质量高.
 
EmployeeDAO:
 
package com.d1zhan;
 
import java.util.List;
 
public class EmployeeDAO extends BaseDAO {
 
    /**
     * searchModel的属性,name,address等为查询参数
     * @param searchModel
     * @return
     */
    public List query(EmployeesearchModel) {
        String sql = "select * from employee where 1=1";
 
        //如果雇员名字不为null,则将雇员名字加入where查询条件
        if (searchModel.getName() !=null) {
            sql += "and employee.name like ‘" + searchModel.getName() + "’ ";
        }
        return this.query(sql,Employee.class);
    }
 
    /**
     * 修改雇员信息
     * @param emp
     * @return
     */
    public boolean edit(Employee emp) {
        String sql = "update employee set ";  //注意: set加在外面
 
        //如果name不为null,修改它的值到数据库
        if (emp.getName() != null) {
            sql +="employee.name=’" + emp.getName() + "’ ,";
        }
 
        //如果address不为null,修改它的值到数据库
        if (emp.getAddress() != null) {
            sql +="employee.address=’" + emp.getAddress() + "’, ";
        }

sql=sql.substring(0,sql.length()-1); //去掉最后一个","
        sql += "where employee.id=" + emp.getId();
        return this.update(sql);
    }
 
    /**
     * 根据雇员ID删除雇员
     * @param id
     * @return
     */
    public boolean delete(int id) {
        String sql = "delete from employee where id =" + id;
        return this.update(sql);
    }
 
    /**
     * 根据雇员ID查找雇员
     * @param id
     * @return
     */
    public Employee get(int id) {
        String sql = "select * from employee where id=" + id;
        return (Employee) this.get(sql,Employee.class);
    }
}
 
3.雇员信息类
 
Employee:
package com.pcm.netrender.model;

public class Employee {
    private int id;
    private String name;
    private String address;
    /**
     * @return
     */
    public String getAddress() {
        return address;
    }
 
    /**
     * @return
     */
    public int getId() {
        return id;
    }
 
    /**
     * @return
     */
    public String getName() {
        return name;
    }
 
    /**
     * @param string
     */
    public void setAddress(String string){
        address = string;
    }
 
    /**
     * @param i
     */
    public void setId(int i) {
        id = i;
   }
 
    /**
     * @param string
     */
    public void setName(String string) {
        name = string;
    }
 
}

4,现在就可以在业务层(service)调用我们的dao类方法，实现业务逻辑了
在service我们要处理业务逻辑，数据库操作事务等等.
然后Struts Action调用 service类的方法，完成软件了.

使用代码大概是这样的

Employeeemp=new Employee();

emp.setName("小李");

emp.setAddress("南宁市阳光新城");

EmployeeDAO dao=new EmployeeDAO();

dao.save(emp);

采用Commons-DbUtils组件(应用数据源)

1.类DBDataSource，用于得到DataSource 对象

publicclass DBDataSource {

private DataSourceds= null ;
 
 public DBDataSource()
 {

Context initContext=new InitialContext();

Contextcontext=(Context)initContext.lookup("java:/comp/env");

ds=(Context)context.lookup("jdbc/sqlds");
   }

// 取得数据源

public DataSource getDataSource()
 {
  return this.ds ;
 }

}

2.查询全部的代码

publicList queryAll() throws Exception {
  // TODO Auto-generated method stub
  List all = new ArrayList() ;
  String sql = "SELECT id,title,author,content FROM note" ;

DBDataSource dbc = new DBDataSource() ;

DataSource ds=dbc.getDataSource();

QueryRunner qr=new QueryRunner(ds);

all=(List)qr.query(sql,newBeanListHandler(Note.class));

return all ; }