jsp的三个指令为：page，include，taglib。。。
建立一个jsp文件，建立起绝对路径，使用时，其他jsp文件导入即可
导入方法：<%@ include file="/commons/common.jsp" %> （这个jsp文件在根目录下的commons文件夹下）
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<base href="${pageContext.request.scheme }://${pageContext.request.serverName }:${pageContext.request.serverPort }${pageContext.request.contextPath}/">
<!-- 其内容先后为：完全的绝对路径：http://.... -->
反射类：通过反射获取其他类中的属性，方法，父类等...
package com.atguigu.bookstore.reflection.utils; import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type; /**
* 反射的 Utils 函数集合
* 提供访问私有变量, 获取泛型类型 Class, 提取集合中元素属性等 Utils 函数
* @author Administrator
*
*/
public class ReflectionUtils { /**
* 通过反射, 获得定义 Class 时声明的父类的泛型参数的类型
* 如: public EmployeeDao extends BaseDao<Employee, String>
* @param clazz
* @param index
* @return
*/
@SuppressWarnings("unchecked")
public static Class getSuperClassGenricType(Class clazz, int index){
Type genType = clazz.getGenericSuperclass(); if(!(genType instanceof ParameterizedType)){
return Object.class;
} Type [] params = ((ParameterizedType)genType).getActualTypeArguments(); if(index >= params.length || index < 0){
return Object.class;
} if(!(params[index] instanceof Class)){
return Object.class;
} return (Class) params[index];
} /**
* 通过反射, 获得 Class 定义中声明的父类的泛型参数类型
* 如: public EmployeeDao extends BaseDao<Employee, String>
* @param <T>
* @param clazz
* @return
*/
@SuppressWarnings("unchecked")
public static<T> Class<T> getSuperGenericType(Class clazz){
return getSuperClassGenricType(clazz, 0);
} /**
* 循环向上转型, 获取对象的 DeclaredMethod
* @param object
* @param methodName
* @param parameterTypes
* @return
*/
public static Method getDeclaredMethod(Object object, String methodName, Class<?>[] parameterTypes){ for(Class<?> superClass = object.getClass(); superClass != Object.class; superClass = superClass.getSuperclass()){
try {
//superClass.getMethod(methodName, parameterTypes);
return superClass.getDeclaredMethod(methodName, parameterTypes);
} catch (NoSuchMethodException e) {
//Method 不在当前类定义, 继续向上转型
}
//..
} return null;
} /**
* 使 filed 变为可访问
* @param field
*/
public static void makeAccessible(Field field){
if(!Modifier.isPublic(field.getModifiers())){
field.setAccessible(true);
}
} /**
* 循环向上转型, 获取对象的 DeclaredField
* @param object
* @param filedName
* @return
*/
public static Field getDeclaredField(Object object, String filedName){ for(Class<?> superClass = object.getClass(); superClass != Object.class; superClass = superClass.getSuperclass()){
try {
return superClass.getDeclaredField(filedName);
} catch (NoSuchFieldException e) {
//Field 不在当前类定义, 继续向上转型
}
}
return null;
} /**
* 直接调用对象方法, 而忽略修饰符(private, protected)
* @param object
* @param methodName
* @param parameterTypes
* @param parameters
* @return
* @throws InvocationTargetException
* @throws IllegalArgumentException
*/
public static Object invokeMethod(Object object, String methodName, Class<?> [] parameterTypes,
Object [] parameters) throws InvocationTargetException{ Method method = getDeclaredMethod(object, methodName, parameterTypes); if(method == null){
throw new IllegalArgumentException("Could not find method [" + methodName + "] on target [" + object + "]");
} method.setAccessible(true); try {
return method.invoke(object, parameters);
} catch(IllegalAccessException e) {
System.out.println("不可能抛出的异常");
} return null;
} /**
* 直接设置对象属性值, 忽略 private/protected 修饰符, 也不经过 setter
* @param object
* @param fieldName
* @param value
*/
public static void setFieldValue(Object object, String fieldName, Object value){
Field field = getDeclaredField(object, fieldName); if (field == null)
throw new IllegalArgumentException("Could not find field [" + fieldName + "] on target [" + object + "]"); makeAccessible(field); try {
field.set(object, value);
} catch (IllegalAccessException e) {
System.out.println("不可能抛出的异常");
}
} /**
* 直接读取对象的属性值, 忽略 private/protected 修饰符, 也不经过 getter
* @param object
* @param fieldName
* @return
*/
public static Object getFieldValue(Object object, String fieldName){
Field field = getDeclaredField(object, fieldName); if (field == null)
throw new IllegalArgumentException("Could not find field [" + fieldName + "] on target [" + object + "]"); makeAccessible(field); Object result = null; try {
result = field.get(object);
} catch (IllegalAccessException e) {
System.out.println("不可能抛出的异常");
} return result;
}
}
需导入dbutils开源包：commons-dbutils-1.3.
jardbutils方法：实现数据库数据的增删改查简便的方法:
package com.atguigu.bookstore.dao.impl; import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.Statement;
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.atguigu.bookstore.dao.DAO;
import com.atguigu.bookstore.dbutils.JDBCUtils;
import com.atguigu.bookstore.reflection.utils.ReflectionUtils;
import com.atguigu.bookstore.web.ConnectionContext; public class BaseDAO<T> implements DAO<T> { private QueryRunner queryRunner=new QueryRunner(); private Class<T> clazz; public BaseDAO(){
//反射类中的反射方法；
clazz=ReflectionUtils.getSuperGenericType(getClass());
} //执行 INSERT 操作, 返回插入后的记录的 ID,使用QueryRunner不能实现有返回值的操作
@Override
public long insert(String sql, Object... args) {
long id=0; Connection connection=null;
PreparedStatement preparedStatement=null;
ResultSet resultSet=null;
try {
connection=ConnectionContext.getInstance().get();
//Statement.RETURN_GENERATED_KEYS,为返回主键
preparedStatement=connection.prepareStatement(sql,Statement.RETURN_GENERATED_KEYS); if(args!=null){
for(int i=0;i<args.length;i++){
preparedStatement.setObject(i+1, args[i]);
}
} preparedStatement.executeUpdate(); //获取生成的主键值
resultSet=preparedStatement.getGeneratedKeys();
if(resultSet.next()){
id=resultSet.getLong(1);
} } catch (Exception e) {
e.printStackTrace();
}finally {
JDBCUtils.release(resultSet, preparedStatement);
}
return id;
} @Override
//执行 UPDATE 操作, 包括 INSERT(但没有返回值), UPDATE, DELETE
public void update(String sql, Object... args) {
Connection connection=null;
try {
connection=ConnectionContext.getInstance().get();
queryRunner.update(connection, sql, args);
} catch (Exception e) {
e.printStackTrace();
} } @Override
//执行单条记录的查询操作, 返回与记录对应的类的一个对象
public T query(String sql, Object... args) {
Connection connection=null;
try {
connection=ConnectionContext.getInstance().get();
return queryRunner.query(connection, sql, new BeanHandler<>(clazz), args);
} catch (Exception e) {
e.printStackTrace();
}
return null;
} @Override
//执行多条记录的查询操作, 返回与记录对应的类的一个 List
public List<T> queryForList(String sql, Object... args) {
Connection connection = null; try {
connection = ConnectionContext.getInstance().get();
return queryRunner.query(connection, sql, new BeanListHandler<>(clazz), args);
} catch (Exception e) {
e.printStackTrace();
}
return null;
} @Override
//执行一个属性或值的查询操作, 例如查询某一条记录的一个字段, 或查询某个统计信息, 返回要查询的值
public <V> V getSingleVal(String sql, Object... args) {
Connection connection=null;
try {
connection=ConnectionContext.getInstance().get();
return (V) queryRunner.query(connection, sql, new ScalarHandler(), args);
} catch (Exception e) {
e.printStackTrace();
}
return null;
} @Override
//执行批量更新操作
public void batch(String sql, Object[]... params) {
Connection connection=null;
try {
connection=ConnectionContext.getInstance().get();
queryRunner.batch(connection, sql, params);
} catch (Exception e) {
e.printStackTrace();
}
} }