JDBC自定义框架
用到的连接池:druid-1.0.9.jar
Druid是阿里巴巴开发的号称为监控而生的数据库连接池，Druid是目前最好的数据库连接池。在功能、性能、扩
展性方面，都超过其他数据库连接池，同时加入了日志监控，可以很好的监控DB池连接和SQL的执行情况。
Druid下载地址:https://github.com/alibaba/druid
提前写好的JdbcUtils类
package com.example.jdbcUtils;
import com.alibaba.druid.pool.DruidDataSourceFactory;
import javax.sql.DataSource;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Properties;
/**
* 该类的作用:
* jdbc工具类
*/
public class JdbcUtils {
private static DataSource dataSource;
static {
try {
//获取src目录下druid连接池的配置文件并创建数据源
InputStream is = JdbcUtils.class.getResourceAsStream("/druid.properties");
Properties properties = new Properties();
properties.load(is);
dataSource= DruidDataSourceFactory.createDataSource(properties);
} catch (Exception e) {
e.printStackTrace();
}
}
//返回当前数据源
public static DataSource getDataSource() {
return dataSource;
}
public static Connection getConnection(){
//获取数据库的连接
try {
return dataSource.getConnection();
} catch (SQLException e) {
throw new RuntimeException(e);
}
}
public static void close(Connection connection,PreparedStatement preparedStatement){
close(connection,preparedStatement,null);
}
public static void close(Connection connection, PreparedStatement preparedStatement, ResultSet resultSet){
//释放资源
if(resultSet!=null){
try {
resultSet.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if(preparedStatement!=null){
try {
preparedStatement.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if(connection!=null){
try {
connection.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
分析：实现框架将分为两大类
1.增删改
2.查询
简单实现增删改功能:
private DataSource dataSource;
//返回当前数据源
public JdbcTemplet(DataSource dataSource) {
this.dataSource=dataSource;
}
public int Update(String sql,Object...params) {
Connection connection = null;
PreparedStatement pstm=null;
try {
connection = dataSource.getConnection();
pstm = connection.prepareStatement(sql);
//查询sql中的占位符个数
ParameterMetaData parameterMetaData = pstm.getParameterMetaData();
int parameterCount = parameterMetaData.getParameterCount();
//判断传入的占位符个数与实际传递的参数个数是否为一致
if (parameterCount != params.length) {
throw new RuntimeException("您的SQL语句中的占位符个数和实际传递的参数数量不一致");
}
//给占位符设置具体的参数值
for (int i = 0; i < parameterCount; i++) {
pstm.setObject(i + 1, params[i]);
}
// 返回影响当前行数的int值
return pstm.executeUpdate();
} catch (SQLException e) {
throw new RuntimeException(e);
}finally {
//释放资源
JdbcUtils.close(connection,pstm);
}
}
测试:
@Test
public void test(){
DataSource dataSource = JdbcUtils.getDataSource();
JdbcTemplet jdbcTemplet = new JdbcTemplet(dataSource);
jdbcTemplet.Update("update product set price=10000 where pid=?", 1);
}
查询功能较复杂:
实现如下：
public Object query(String sql,ResultSetHandler handler, Object...params){
Connection connection=null;
PreparedStatement pstm=null;
ResultSet resultSet=null;
try {
connection= dataSource.getConnection();
pstm =connection.prepareStatement(sql);
//查询sql中的占位符个数
ParameterMetaData parameterMetaData = pstm.getParameterMetaData();
int parameterCount = parameterMetaData.getParameterCount();
//判断传入的占位符个数与实际传递的参数个数是否为一致
if(parameterCount!=params.length){
throw new RuntimeException("您的SQL语句中的占位符个数和实际传递的参数数量不一致");
}
//给占位符设置具体的参数值
for (int i = 0; i ResultSetHandler接口
public interface ResultSetHandler {
Object handle(ResultSet rs);
}
编写封装一个对象的处理器
**public class BeanHandler implements ResultSetHandler {
private Class clazz;
//返回具体的封装类型
public BeanHandler(Class clazz){
this.clazz=clazz;
}
@Override
public Object handle(ResultSet rs) {
try {
if (!rs.next()){
return null;
}
Object bean = clazz.newInstance();//获取传入对象的一个实例
//封装数据到bean中
//前提：数据库字段名和JavaBean的字段名保持了一致
ResultSetMetaData rsmd = rs.getMetaData();
int count = rsmd.getColumnCount();//列数
for (int i = 0; i javaBean
public class Product {
private int pid;
private String pname;
private double price;
@Override
public String toString() {
return "Product{" +
"pid=" + pid +
", pname='" + pname + '\'' +
", price=" + price +
'}';
}
public int getPid() {
return pid;
}
public void setPid(int pid) {
this.pid = pid;
}
public String getPname() {
return pname;
}
public void setPname(String pname) {
this.pname = pname;
}
public double getPrice() {
return price;
}
public void setPrice(double price) {
this.price = price;
}
public Product() {
}
}
测试:
@Test
public void test4() {
DataSource dataSource = JdbcUtils.getDataSource();
JdbcTemplet jdbcTemplet = new JdbcTemplet(dataSource);
Object query = jdbcTemplet.query("select * from product where pid=?", new BeanHandler(Product.class), 2);
System.out.println(query);
}
封装多条记录的处理器
原理如上，将返回的bean对象增加到LIST集合中并返回.
public class BeanListHandler implements ResultSetHandler {
private Class clazz;
public BeanListHandler(Class clazz) {
this.clazz = clazz;
}
@Override
public Object handle(ResultSet rs) {
try {
List list = new ArrayList<>();
while (rs.next()) {
System.out.println();
Object bean = clazz.newInstance();
ResultSetMetaData rsmd = rs.getMetaData();
int count = rsmd.getColumnCount();
for (int i = 0; i < count; i++) {
String columnName = rsmd.getColumnName(i + 1);
Object columnData = rs.getObject(i + 1);
System.out.println(columnName + columnData);
Field field = clazz.getDeclaredField(columnName);
field.setAccessible(true);
field.set(bean, columnData);
}
list.add(bean);
}
return list;
} catch (Exception e) {
throw new RuntimeException("封装数据失败，请检查您的bean是否符合限制条件",e);
}
}
}
测试
@Test
public void test5() {
DataSource dataSource = JdbcUtils.getDataSource();
JdbcTemplet jdbcTemplet = new JdbcTemplet(dataSource);
Object query = jdbcTemplet.query("select * from product", new BeanListHandler(Product.class));
System.out.println(query);
}