</pre><pre>
package trade.axht.java.dao;
import org.apache.commons.beanutils.BeanUtils;
import org.apache.commons.dbutils.QueryRunner;
import trade.axht.java.conn.JDBCUtils;
import java.util.*;
import java.lang.reflect.*;
import java.sql.*;
/**
*
*基类带泛型，派生类可以带泛型参数继承该类，通过反射对Beans对象操作
* @author Administrator
*
* @param <T>
*/
public class DAO<T> {//带泛型的基类，派生类可以带具体beans泛型参数继承该类
public Class<T> clazz;
@SuppressWarnings({ "unchecked", "rawtypes" })
public DAO(){
System.out.println(getClass()); //打印class trade.axht.java.dao.userImpl.****DaoImpl
Type type=getClass().getGenericSuperclass();
System.out.println(type);
/**获取继承【该类(DAO<T>)】带具体泛型的基类 或者获取此类的基类（Object)，简单的讲就是谁继承Dao<T>这个类后，在加载的时候，就会来加载这个构造函数。加载class的对象为Dao<T>的派生类。派生类的基类就是Dao<T>,并能获取基类带有的具体泛型。
JDK文档描述是这样的：返回表示此Class所表示的实体（类、接口、基本类型或 void）的直接超类的Type。如果超类是参数化类型，则返回的对象必须准确反映源///代码中所使用的实际类型参数。
所以最终打印为**/
ParameterizedType parameterizedType=(ParameterizedType)type;//ParameterizedType 表示参数化类型，如 Collection<String>。
System.out.println(parameterizedType);
Type[] ars=parameterizedType.getActualTypeArguments();/**返回表示此类型实际类型参数的对象的数组。就是返回Collection<T,V,...>中的泛型参数T,V类型的Type表示形式。Type 是 Java 编程语言中所有类型的公共高级接口。它们包括原始类型、参数化类型、数组类型、类型变量和基本类型。**/
System.out.println(ars);
clazz=(Class) ars[0];//获取泛型参数的第一个Class对象
System.out.println(clazz);
// System.out.println(clazz);
}
/**
* 增，删，改操作
* @param sql
* @param args
* @return
*/
public int executeUpdate(String sql,Object...args){
Connection connection=JDBCUtils.getConnection();
PreparedStatement preparedStatement=null;
try {
preparedStatement=connection.prepareStatement(sql);
if(args!=null&&args.length>0){
for(int i=0;i<args.length;i++){
preparedStatement.setObject(i+1, args[i]);
}
}
return preparedStatement.executeUpdate();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
return -1;
}finally {
JDBCUtils.releaseConnection(connection, preparedStatement, null);
}
}
/**
* 查询
* @param clazz
* @param sql
* @param args
* @return
*/
public List<T> getForList(String sql, Object... args) {
List<T> list = new ArrayList<>();
Connection connection = null;
PreparedStatement preparedStatement = null;
ResultSet resultSet = null;
try {
//1. 得到结果集
connection = JDBCUtils.getConnection();
preparedStatement = connection.prepareStatement(sql);
if(args!=null&&args.length>0){
for (int i = 0; i < args.length; i++) {
preparedStatement.setObject(i + 1, args[i]);
}
}
resultSet = preparedStatement.executeQuery();
//2处理结果解，得到Map的list，其中一个Map对象就是一条记录。
//Map的key为resultSet中的列的别名，Map的value为列的值
List<Map<String, Object>> values =
handleResultSetToMapList(resultSet);
//3.把List<Map<String,Object>> 转化成Class对象(clazz)的实例集List<T>
list = transfterMapListToBeanList( values);
} catch (Exception e) {
e.printStackTrace();
} finally {
JDBCUtils.releaseConnection(connection,preparedStatement,resultSet);
}
return list;
}
public List<T> transfterMapListToBeanList(List<Map<String, Object>> values) throws InstantiationException,
IllegalAccessException, InvocationTargetException {
List<T> result = new ArrayList<>();
T bean = null;
if (values.size() > 0) {
for (Map<String, Object> m : values) {
bean = clazz.newInstance();
for (Map.Entry<String, Object> entry : m.entrySet()) {
String propertyName = entry.getKey();
Object value = entry.getValue();
//利用org.apache.commons.beanutils.BeanUtils工具类反射设置对象属性
BeanUtils.setProperty(bean, propertyName, value);
/* try {
ReflectorUtil.setProperty(bean, propertyName, value);
} catch (NoSuchFieldException | SecurityException | IllegalArgumentException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}*/
}
result.add(bean);
}
}
return result;
}
public List<Map<String, Object>> handleResultSetToMapList(
ResultSet resultSet) throws SQLException {
List<Map<String, Object>> values = new ArrayList<>();
//获取列名
List<String> columnLabels = getColumnLabels(resultSet);
Map<String, Object> map = null;
while (resultSet.next()) {
map = new HashMap<>();
for (String columnLabel : columnLabels) {
Object value = resultSet.getObject(columnLabel);
map.put(columnLabel, value);
}
values.add(map);
}
return values;
}
private List<String> getColumnLabels(ResultSet rs) throws SQLException {
List<String> labels = new ArrayList<>();
ResultSetMetaData rsmd = rs.getMetaData();
for (int i = 0; i < rsmd.getColumnCount(); i++) {
labels.add(rsmd.getColumnLabel(i + 1));
}
return labels;
}
public int getCount(String sql,String...id){
Connection connection=null;
ResultSet resultSet=null;
PreparedStatement preparedStatement=null;
try {
connection=JDBCUtils.getConnection();
resultSet=null;
preparedStatement=connection.prepareStatement(sql);
if(id!=null&&id.length>0){
for(int i=1;i<=id.length;i++)
preparedStatement.setString(i, id[i-1]);
}
resultSet=preparedStatement.executeQuery();
if(resultSet.next()){
return resultSet.getInt(1);
}
else {
return 0;
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
return 0;
}finally{
JDBCUtils.releaseConnection(connection, preparedStatement, resultSet);
}
}
}
定义ManagerDaoImpl,该类继承与Dao
package trade.axht.java.dao.userImpl;
import trade.axht.java.dao.DAO;
import trade.axht.java.dao.ManagerDAO;
import trade.axht.java.domain.Manager;
public class ManagerDaoImpl extends DAO<Manager> {
@Override
public int getCount(Manager manager) {
// TODO Auto-generated method stub
String sql="select Count(*) from tb_manager where username=? and password=?";
return getCount(sql, manager.getUsername(),manager.getPassword());
}
}
Beans类型的Manager类
package trade.axht.java.domain;
public class Manager {
private int id;
private String username;
private String password;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public Manager() {
super();
// TODO Auto-generated constructor stub
}
public Manager(int id, String username, String password) {
super();
this.id = id;
this.username = username;
this.password = password;
}
}
数据库连接操作类
package trade.axht.java.conn;
import javax.sql.*;
import java.sql.*;
import java.util.*;
import java.io.*;
public class JDBCUtils {
private static DataSource dataSource=null;
static{
Properties properties=new Properties();
InputStream in=JDBCUtils.class.getClassLoader().getResourceAsStream("dbcp.properties");//加载配置文件
try {
<span style="white-space:pre"> </span>properties.load(in);
dataSource=org.apache.commons.dbcp2.BasicDataSourceFactory.createDataSource(properties);//利用数据库连接池(dbcp2)获取数据源
} catch (Exception e) {
// TODO Auto-generated catch block
System.out.println("数据库连接出错!");
e.printStackTrace();
}
}
public static Connection getConnection(){
try {
return dataSource.getConnection();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
return null;
}
}
public static void releaseConnection(Connection connection,Statement statement,ResultSet resultSet) {
if (connection!=null) {
try {
connection.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
if (statement!=null) {
try {
statement.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
if (resultSet!=null) {
try {
resultSet.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
数据库配置文件 jdcp.properties
driverClassName=com.mysql.jdbc.Driver url=jdbc:mysql://localhost:3306/blog username=root password=brozer initialSize=5 maxIdle=10 maxTotal=50 maxWaitMillis=5000 minIdle=5
导入的包
时间： 2024-10-01 07:57:31