java操作数据库的通用的类

package cn.dao;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.math.BigDecimal;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
/**
* 数据库操作通用类
* @author tip
*/
public class DBHelp {
private Connection con;
private PreparedStatement ps;
private ResultSet rs;
static Readdoc td = new Readdoc();//读取XML文件中的数据库连接参数
static {
try {
Class.forName(td.getDriver());
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}
public Connection getCon() throws SQLException {
con = DriverManager.getConnection("jdbc:oracle:thin:@" + td.getAdd()
+ ":1521:" + td.getDb(), td.getUname(), td.getPwd());
return con;
}
public <T> List<T> findBySql(String sql, List<String> params, Class<T> c)
throws SQLException {
List<T> list = new ArrayList<T>();
// 取出c的这个对象中有多少个方法
Method[] ms = c.getMethods();
con = this.getCon();
try {
ps = con.prepareStatement(sql);
this.doParams(ps, params);
rs = ps.executeQuery();
// 得到db中的表的列
ResultSetMetaData rsmd = rs.getMetaData();
// 存储全部的列名
String[] columnname = new String[rsmd.getColumnCount()];
for (int i = 0; i < columnname.length; i++) {
columnname[i] = rsmd.getColumnName(i + 1);
}
// id=> "set"+"I"+d=> "setId()" =>对应数据库表的字段
while (rs.next()) {
// new对象
T t = c.newInstance(); // Topic t=new Topic();
// t.setId(rs.getInt("id"));
for (int i = 0; i < columnname.length; i++) {
String cn = columnname[i]; // id title contents
cn = "set" + cn.substring(0, 1).toUpperCase()
+ cn.substring(1).toLowerCase(); // "setId"
for (Method m : ms) {
if (m.getName().equals(cn)) {
if (rs.getObject(columnname[i]) != null) {
if ("java.sql.Timestamp".equals(rs.getObject(columnname[i]).getClass().getName())) {
m.invoke(t, rs.getString(columnname[i]));
} else if ("java.lang.Integer".equals(rs.getObject(columnname[i]).getClass().getName())) {
m.invoke(t, rs.getInt(columnname[i]));
} else {
m.invoke(t, rs.getObject(columnname[i]));
}
} else {
m.invoke(t, rs.getObject(columnname[i]));
}
break;
}
}
}
list.add(t);
}
} catch (IllegalArgumentException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
} catch (InstantiationException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
} finally {
closeAll(rs, ps, con);
}
return list;
}
// insert into xx values(?,?); params={"tip","whx"};
public <T> int doUpdate(String sql, List<T> params) throws SQLException {
con = this.getCon();
int i = 0;
try {
ps = con.prepareStatement(sql);
doParams(ps, params);
i = ps.executeUpdate();
} catch (SQLException e) {
try {
con.rollback();
} catch (SQLException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
} finally {
closeAll(null, ps, con);
}
return i;
}
// 设置预编译对象参数
public <T> void doParams(PreparedStatement pstmt, List<T> params)
throws SQLException {
if (pstmt != null && params != null && params.size() > 0) {
for (int i = 0; i < params.size(); i++) {
if (params.get(i) != null) {
if (params.get(i).getClass().getName().equals("java.lang.String")) {
pstmt.setString(i + 1, (String) params.get(i));
} else if (params.get(i).getClass().getName()
.equals("java.math.BigDecimal")) {
pstmt.setBigDecimal(i + 1, (BigDecimal) params.get(i));
} else if (params.get(i).getClass().getName().equals("java.sql.Timestamp")) {
pstmt.setString(i + 1, (String) params.get(i));
} else {
pstmt.setObject(i + 1, params.get(i));
}
} else {
pstmt.setString(i + 1, "");
}
}
}
}
public void closeAll(ResultSet rs, PreparedStatement pstmt, Connection con) {
if (rs != null) {
try {
rs.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (pstmt != null) {
try {
pstmt.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (con != null) {
try {
con.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}