1.DBUtil类

package com.cdsxt.util;

import java.io.InputStream;

import java.sql.Connection;

import java.sql.DriverManager;

import java.sql.ResultSet;

import java.util.Properties;

import com.mysql.jdbc.PreparedStatement;

public class DBUtil {

private static String mysqlDriver;

private static String url;

private static String user;

private static String password;

static{

try {

InputStream is=DBUtil.class.getResourceAsStream("/db.properties");

Properties ps=new Properties();

ps.load(is);

mysqlDriver=ps.getProperty("mysqlDriver");

url=ps.getProperty("url");

user=ps.getProperty("user");

password=ps.getProperty("password");

Class.forName(mysqlDriver);

} catch (Exception e) {

e.printStackTrace();

}

}

//获取数据库连接

public static Connection getConn(){

Connection conn=null;

try {

conn= DriverManager.getConnection(url, user, password);

} catch (Exception e) {

e.printStackTrace();

System.out.println("获取数据库链接异常");

}

return conn;

}

//关闭资源

public static void close(Object...objs){

if(objs!=null&&objs.length>0){

for(int i=0;i<objs.length;i++){

try {

if(objs[i] instanceof Connection){

((Connection)objs[i]).close();

}else if(objs[i] instanceof PreparedStatement){

((PreparedStatement)objs[i]).close();

}else if(objs[i] instanceof ResultSet){

((ResultSet)objs[i]).close();

}

} catch (Exception e) {

e.printStackTrace();

System.out.println("关闭资源 异常");

}

}

}

}

}

2.封装代码;

package com.cdsxt.base;

import java.lang.reflect.Field;

import java.lang.reflect.Method;

import java.lang.reflect.ParameterizedType;

import java.lang.reflect.Type;

import java.sql.Connection;

import java.sql.PreparedStatement;

import java.sql.ResultSet;

import java.sql.ResultSetMetaData;

import java.util.ArrayList;

import java.util.List;

import com.cdsxt.po.Person;

import com.cdsxt.util.DBUtil;

//基于泛型类

public class BaseDao3<T> {

Class<T> clazz;

public BaseDao3(){

Type type=this.getClass().getGenericSuperclass();

Type[] types=((ParameterizedType)type).getActualTypeArguments();

clazz=(Class<T>)types[0];

}

//查询表带参数

public List<T> queryList(T t){

Connection conn=null;

PreparedStatement ps=null;

ResultSet rs=null;

String sql=getQuerySql(t);

List<T> list=new ArrayList<T>();

try {

conn=DBUtil.getConn();

ps=conn.prepareStatement(sql);

Field[] fields=clazz.getDeclaredFields();

int c=1;

for(int i=0;i<fields.length;i++){

fields[i].setAccessible(true);

//填坑

if(fields[i].get(t)!=null){

String fieldName=fields[i].getName();

Method method=clazz.getMethod(getGetter(fieldName));

Object obj=method.invoke(t);

ps.setObject(c, obj);

fields[i].setAccessible(false);

c++;

}

}

rs=ps.executeQuery();

ResultSetMetaData metaData=rs.getMetaData();

int count=metaData.getColumnCount();

while(rs.next()){

T obj=(T)clazz.newInstance();

for(int i=0;i<count;i++){

String fieldName=metaData.getColumnName(i+1);

Field field=clazz.getDeclaredField(fieldName);

Method method=clazz.getMethod(getSetter(fieldName), field.getType());

method.invoke(obj, rs.getObject(i+1));

}

list.add(obj);

}

} catch (Exception e) {

e.printStackTrace();

}finally{

DBUtil.close(rs,ps,conn);

}

return list;

}

//查询单个po

public T queryPo(int id){

Connection conn=null;

PreparedStatement ps=null;

ResultSet rs=null;

T t=null;

String sql="select * from "+clazz.getSimpleName()+" where  id=?";

try {

t=(T)clazz.newInstance();

conn=DBUtil.getConn();

ps=conn.prepareStatement(sql);

ps.setInt(1, id);

rs=ps.executeQuery();

ResultSetMetaData metaData =rs.getMetaData();

int count=metaData.getColumnCount();

while(rs.next()){

for(int i=0;i<count;i++){

String fieldName=metaData.getColumnName(i+1);

Field filed =clazz.getDeclaredField(fieldName);

Method method=clazz.getMethod(getSetter(fieldName), filed.getType());

method.invoke(t, rs.getObject(i+1));

}

}

} catch (Exception e) {

e.printStackTrace();

}finally{

DBUtil.close(rs,ps,conn);

}

return t;

}

//获取符合条件的po 个数

public int queryCount(T t){

return queryList(t).size();

}

//添加po

public void insertPo(T t){

Connection conn=null;

PreparedStatement ps=null;

String sql=getInsertSql(t);

try {

conn=DBUtil.getConn();

ps=conn.prepareStatement(sql);

Field[] fields=clazz.getDeclaredFields();

int c=1;

//填坑

for(int i=0;i<fields.length;i++){

fields[i].setAccessible(true);

//填坑

if(fields[i].get(t)!=null){

String fieldName=fields[i].getName();

Method method=clazz.getMethod(getGetter(fieldName));

Object obj=method.invoke(t);

ps.setObject(c, obj);

fields[i].setAccessible(false);

c++;

}

}

ps.execute();

} catch (Exception e) {

e.printStackTrace();

}finally{

DBUtil.close(ps,conn);

}

}

//修改po

public void updatePo(T t,int id){

Connection conn=null;

PreparedStatement ps=null;

String sql=getUpdateSql(t, id);

try {

conn=DBUtil.getConn();

ps=conn.prepareStatement(sql);

Field[] fields=clazz.getDeclaredFields();

int c=1;

//填坑

for(int i=0;i<fields.length;i++){

fields[i].setAccessible(true);

//填坑

if(fields[i].get(t)!=null){

String fieldName=fields[i].getName();

Method method=clazz.getMethod(getGetter(fieldName));

Object obj=method.invoke(t);

ps.setObject(c, obj);

fields[i].setAccessible(false);

c++;

}

}

ps.setInt(c, id);

ps.execute();

} catch (Exception e) {

e.printStackTrace();

}finally{

DBUtil.close(ps,conn);

}

}

//删除

public void deletePo(int id){

Connection conn=null;

PreparedStatement ps=null;

String sql="delete from "+clazz.getSimpleName()+"  where id=?";

System.out.println(sql);

try {

conn=DBUtil.getConn();

ps=conn.prepareStatement(sql);

ps.setInt(1, id);

ps.execute();

} catch (Exception e) {

e.printStackTrace();

}finally{

DBUtil.close(ps,conn);

}

}

//获取查询的sql语句

public  String getQuerySql(T t){

String sql="select * from "+clazz.getSimpleName()+"  where 1=1 ";

try {

Field[] fields=clazz.getDeclaredFields();

for(int i=0;i<fields.length;i++){

fields[i].setAccessible(true);

if(fields[i].get(t)!=null){

sql+= " and " +fields[i].getName()+"=?";

}

}

sql=sql.substring(0,sql.length());

} catch (Exception e) {

e.printStackTrace();

}

return sql;

}

//获取添加的sql语句

public String getInsertSql(T t){

String sql="insert into "+clazz.getSimpleName()+"(";

String param="";

Field[] fields=clazz.getDeclaredFields();

try {

for(int i=0;i<fields.length;i++){

fields[i].setAccessible(true);

if(fields[i].get(t)!=null){

sql+=fields[i].getName()+",";

param+="?,";

}

}

sql=sql.substring(0,sql.length()-1)+") values("+param;

sql=sql.substring(0,sql.length()-1)+")";

} catch (Exception e) {

e.printStackTrace();

}

return sql;

}

//获取修改的sql语句

public String getUpdateSql(T t,int id){

String sql="update "+clazz.getSimpleName()+" set ";

Field[] fields=clazz.getDeclaredFields();

try {

for(int i=0;i<fields.length;i++){

fields[i].setAccessible(true);

if(fields[i].get(t)!=null){

sql+=fields[i].getName()+"=?,";

}

}

} catch (Exception e) {

e.printStackTrace();

}

sql=sql.substring(0,sql.length()-1)+"  where id =?";

return sql;

}

//获取set方法的方法名

public static String getSetter(String fieldName){

//传入属性名 拼接set方法  

return "set"+fieldName.substring(0,1).toUpperCase()+fieldName.substring(1);

}

//获取get方法的方法名

public static String getGetter(String fieldName){

//传入属性名 拼接set方法  

return "get"+fieldName.substring(0,1).toUpperCase()+fieldName.substring(1);

}

}

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作者：mischen520 

来源：CSDN 

原文：https://blog.csdn.net/miachen520/article/details/52057955 

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