基于DBUtils的数据库工具类实现

Commonsdbutils是什么？

commons-dbutils 是 Apache 组织提供的一个开源 JDBC 工具类库，对传统操作数据库的类进行二次封装，可以把结果集转化成List。并且使用dbutils能极大简化jdbc编码的工作量，同时也不会影响程序的性能。因此dbutils成为很多不喜欢hibernate的公司的首选。

准备

由于使用Oracle数据库 和c3p0数据源 我们要

导入以下jar包

c3p0-0.9.5.1.jar

commons-dbutils-1.3.jar

ojdbc6.jar

c3p0配置文件

c3p0.jdbcUrl=jdbc:oracle:thin:test/test@localhost:1521:orcl

c3p0.driverClass=oracle.jdbc.OracleDriver

c3p0.initialPoolSize=6

c3p0.acquireIncrement=6

c3p0.minPoolSize=6

数据库连接工具类JdbcUtils

#### package com.mav.db;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

import javax.sql.DataSource;

import com.mchange.v2.c3p0.ComboPooledDataSource;

public class JdbcUtils {
/**
* dbUtils 不需要关resultset
* 释放 Connection 连接
* @param connection
*/
public static void releaseConnection(Connection connection){
try {
if(connection != null){
connection.close();
}
} catch (Exception e) {
e.printStackTrace();
}
}
private static DataSource ds = new ComboPooledDataSource();
public static Connection getConnection() throws SQLException{

return ds.getConnection();
}
public static void free(ResultSet rs, Statement stmt, Connection conn) {
if (rs != null) {
try {
rs.close();
} catch (SQLException e) {

e.printStackTrace();
}
}
if (stmt != null) {
try {
stmt.close();
} catch (SQLException e) {

e.printStackTrace();
}
}
if (conn != null) {
try {
conn.close();
} catch (SQLException e) {

e.printStackTrace();
}
}
}

}

####接下来就是编写使用dbutils来进行CURD操作的工具类了

其中dbutils的一些方法的使用大家可以看我写的 模仿dbutils的jdbc框架 这篇文章

该类使用了泛型 T 代表传入的实体类类型

package com.mav.dao;

import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.sql.Connection;
import java.util.List;

import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanHandler;
import org.apache.commons.dbutils.handlers.BeanListHandler;
import org.apache.commons.dbutils.handlers.ScalarHandler;

import com.mav.db.JdbcUtils;

/**
* 封装了基本的 CRUD 的方法, 以供子类继承使用
* 当前 DAO 直接在方法中获取数据库连接.
* 整个 DAO 采取 DBUtils 解决方案.
* @param <T>: 当前 DAO 处理的实体类的类型是什么
*/
public class Dao<T> {

private QueryRunner queryRunner = new QueryRunner();

private Class<T> clazz;

public Dao() {
Type superClass = this.getClass().getGenericSuperclass();
if(superClass instanceof ParameterizedType){
ParameterizedType parameterizedType = (ParameterizedType) superClass;
Type[] typeArgs = parameterizedType.getActualTypeArguments();
if(typeArgs != null && typeArgs.length>0){
if(typeArgs[0] instanceof Class){
clazz = (Class<T>) typeArgs[0];
System.out.println("dao类中的构造方法泛型类型："+clazz.getName());
}
}
}
}

/**
* 返回某一个字段的值：例如返回某一条记录的 customerName, 或返回数据表中有多少条记录等.
* @param sql
* @param args
* @return
*/
public <E> E getForValue(String sql,Object ...args){
Connection conn = null;
try {

conn = JdbcUtils.getConnection();

return (E) queryRunner.query(conn, sql,new ScalarHandler(), args);

} catch (Exception e) {
e.printStackTrace();
}finally{
JdbcUtils.releaseConnection(conn);
}
return null;
}

/**
* 返回 T 所对应的 List
* @param sql
* @param args
* @return
*/
public List<T> getForList(String sql,Object ...args){
Connection conn = null;
try {
conn = JdbcUtils.getConnection();
return queryRunner.query(conn, sql,new BeanListHandler<>(clazz), args);

} catch (Exception e) {
e.printStackTrace();
}finally{
JdbcUtils.releaseConnection(conn);
}
return null;
}

/**
* 返回对应的 T 的一个实例类的对象.
* @param sql
* @param args
* @return
*/

public T get(String sql ,Object ...args){
Connection conn = null;
try {
conn = JdbcUtils.getConnection();
return queryRunner.query(conn, sql,new BeanHandler<>(clazz), args);

} catch (Exception e) {
e.printStackTrace();
}finally{
JdbcUtils.releaseConnection(conn);
}
return null;
}

/**
* 该方法封装了 INSERT、DELETE、UPDATE 操作.
* @param sql: SQL 语句
* @param args: 填充 SQL 语句的占位符.
*/
public void Update(String sql,Object ...args){
Connection conn = null;
try {
conn = JdbcUtils.getConnection();
queryRunner.update(conn, sql, args);

} catch (Exception e) {
e.printStackTrace();
}finally{
JdbcUtils.releaseConnection(conn);
}
}
}

以上的代码时可以重复利用的

具体进行数据库操作的接口

package com.mav.dao;

import java.util.List;

import com.mav.domain.CriteriaCustomer;
import com.mav.domain.Customer;

public interface CustomerDao {

/**
* 返回满足查询条件的 List
* @param cc: 封装了查询条件
* @return
*/
public List<Customer> getForListByCriteriaCustomer(CriteriaCustomer cc);
public List<Customer> getALl();

public void save(Customer customer);

public Customer get(Integer id);

public void delete(Integer id);

/**
* 返回和 name 相等的记录数.
* @param name
* @return
*/
public Long getCountWithName(String name);
public void update(Customer customer);

}

#### 与数据表对应的实体类

package com.mav.domain;

public class Customer {
private Integer id;
private String name;
private String address;
private String phone;

public Customer() {
// TODO Auto-generated constructor stub
}

public Customer(Integer id, String name, String address, String phone) {
super();
this.id = id;
this.name = name;
this.address = address;
this.phone = phone;
}

public Integer getId() {
return id;
}

public String getName() {
return name;
}

public String getAddress() {
return address;
}

public String getPhone() {
return phone;
}

public void setId(Integer id) {
this.id = id;
}

public void setName(String name) {
this.name = name;
}

public void setAddress(String address) {
this.address = address;
}

public void setPhone(String phone) {
this.phone = phone;
}

@Override
public String toString() {
return "Customer [id=" + id + ", name=" + name + ", address=" + address + ", phone=" + phone + "]";
}

}

#### CustomerDao 的实现类

实现类CustomerDao 并继承了Dao<>类

package com.mav.dao.impl;

import java.math.BigDecimal;
import java.util.List;

import com.mav.dao.CustomerDao;
import com.mav.dao.Dao;
import com.mav.domain.CriteriaCustomer;
import com.mav.domain.Customer;

public class CustomerDaoJdbcImpl extends Dao<Customer> implements CustomerDao {

public List<Customer> getForListByCriteriaCustomer(CriteriaCustomer cc) {
String sql = "select id,name,address,phone from customers where name like ? and address like ? and phone like ?";
//这样写太麻烦了   我们可以修改CriteriaCustomer 类中的get方法来获得
//return getForList(sql,"%"+ cc.getName()+"%","%"+ cc.getAddress()+"%","%"+ cc.getPhone()+"%");
return getForList(sql, cc.getName(),cc.getAddress(),cc.getPhone());
}

@Override
public List<Customer> getALl() {
String sql = "select id,name,address,phone from customers";
return getForList(sql);
}

@Override
public void save(Customer customer) {
String sql = "insert into customers values(null,?,?,?)";
Update(sql,customer.getName(),customer.getAddress(),customer.getPhone());

}

@Override
public Customer get(Integer id) {
String sql ="select id,name,address,phone from customers where id = ?";

return get(sql, id);
}

@Override
public void delete(Integer id) {
String sql = "delete from customers where id = ?";
Update(sql, id);

}

@Override
public Long getCountWithName(String name) {
String sql = "select count(id) from customers where name = ?";
BigDecimal b = getForValue(sql, name);
//BigDecimal 从数据库返回的类型为此 须强转       也可以返回值为 number 类型
return b.longValue();
}

@Override
public void update(Customer customer) {
String sql ="update customers set name = ? , address = ? , phone = ? where id = ?";
Update(sql, customer.getName(),customer.getAddress(),customer.getPhone(),customer.getId());

}

}

## ##测试 ##

package com.mav.test;

import java.util.List;

import org.junit.Test;

import com.mav.dao.CustomerDao;
import com.mav.dao.impl.CustomerDaoJdbcImpl;
import com.mav.domain.Customer;

import junit.framework.TestCase;

public class CustomerDaoJdbcImplTest extends TestCase {
private  CustomerDao customerDao = new CustomerDaoJdbcImpl();

@Test
public void testAdd(){
Customer customer = new Customer();
customer.setAddress("china");
customer.setName("liming");
customer.setPhone("15088789250");
customerDao.save(customer);
}
@Test
public void testGetList(){
List<Customer> list = customerDao.getALl();
for(Customer c : list){
System.out.println(c);
}
}
/* 输出结果
Customer [id=18, name=update, address=qwewqweq, phone=121343121]
Customer [id=9, name=里面, address=南阳, phone=12121212]
Customer [id=12, name=行云, address=西安, phone=123456]
Customer [id=19, name=zli123, address=beijing, phone=110120119454]
Customer [id=17, name=zhognfd, address=sdfsd, phone=123]
Customer [id=11, name=重视, address=北京, phone=12121212]

*/
@Test
public void testGetbyId(){
Customer customer = customerDao.get(3);
System.out.println(customer);
}
@Test
public void testDeletebyId(){
customerDao.delete(3);

}
@Test
public void testgetCountWithName(){
Long count =  customerDao.getCountWithName("222");
System.out.println(count);
}
}

关于dbutils的介绍就到这了，有什么错误的地方还请包含并指出