java--分析简单java类与反射的联系

分析简单java类与反射的联系

web对反射的操作支持

在JSP之中有一种技术--javaBean。而且在jsp里面也配套有相应的操作方式，javaBean的核心在于简单java类，于是下面演示此操作

代码示例：创建一个简单的Student类

package com.hbsi.domain;

public class Student {

 public Student() {

 System.out.println("构造方法执行了，对象实例化");

 }

 private String name;

 private Integer age;

 private String sex;

 public String getName() {

 System.out.println("getName被调用");

 return name;

 }

 public void setName(String name) {

 System.out.println("setName被调用");

 this.name = name;

 }

 public Integer getAge() {

 System.out.println("getAge被调用");

 return age;

 }

 public void setAge(Integer age) {

 System.out.println("setAge被调用");

 this.age = age;

 }

 public String getSex() {

 System.out.println("getSex被调用");

 return sex;

 }

 public void setSex(String sex) {

 System.out.println("setSex被调用");

 this.sex = sex;

 }

}

在web项目中所建立的每个java类最终都会保存在WEB-INF/classes目录下，所以classes就是一个CLASSPATH。但是要求是：

建立一个表单，输入完成后的数据需要设置到Student类中，同时再通过Student类对象取得输入内容

代码范例：定义一个输入表单

<%@ page language="java" contentType="text/html; charset=UTF-8"

 pageEncoding="UTF-8"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<html>

<head>

<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">

<title>student_insert.jsp</title>

</head>

<body>

<h1>纯菜鸟</h1>

 <form action="student_insert_do.jsp" method="post">

 姓名：<input type="text" name="name"><br/>

 年龄：<input type="text" name="age"><br/>

 性别：<input type="text" name="sex"><br/>

 <input type="submit" value="确定">

 <input type="reset"><br/>

 </form>

</body>

</html>

此时Student类已经生成了对应的setter 和 getter方法，同时表单中的参数名与Student中的属性名一致，

代码范例：按照传统方式编写一个接受页面

<%@ page language="java" contentType="text/html; charset=UTF-8"

 pageEncoding="UTF-8"%>

<%@ page import="com.hbsi.domain.Student"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<html>

<head>

<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">

<title>Insert title here</title>

</head>

<body>

 <%

 request.setCharacterEncoding("UTF-8");

 Student stu = new Student();

 stu.setName(request.getParameter("name"));

 stu.setAge(Integer.parseInt(request.getParameter("age")));

 stu.setSex(request.getParameter("sex"));

 %>

 <h1>Name:<%=stu.getName()%></h1>

 <h1>Age :<%=stu.getAge() %></h1>

 <h1>Sex :<%=stu.getSex() %></h1>

</body>

</html>

将此项目放到Tomcat中并且运行项目并输入，“懒蛋，18，男”执行结果如下

但是如果直接使用JSP的开发方式，以上的代码就可以简化了

代码范例编写简化后的JSP页面

<%@ page language="java" contentType="text/html; charset=UTF-8"

 pageEncoding="UTF-8"%>

<%@ page import="com.hbsi.domain.Student"%>

<% request.setCharacterEncoding("UTF-8"); %>

<jsp:useBean id="stu" class="com.hbsi.domain.Student" scope="page"/>

<jsp:setProperty property="*" name="stu"/>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<html>

<head>

<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">

<title>Insert title here</title>

</head>

<body>

 <%

 request.setCharacterEncoding("UTF-8");

 %>

 <h1>Name:<jsp:getProperty property="name" name="stu"/></h1>

 <h1>Age :<jsp:getProperty property="age" name="stu"/></h1>

 <h1>Sex :<jsp:getProperty property="sex" name="stu"/></h1>

</body>

</html>

执行程序并输入“懒蛋，19，jj” 运行结果如下

下面来看一下使用到的三个标签

1. 定义javaBean对象：

<jsp:useBean id="stu" class="com.hbsi.domain.Student" scope="page"/>

1. id：表示定义的实例化名字，Student stu = new Student();

2. class：对象的类型。此处是依靠反射实例化对象；（调用无参构造）

3. scope：此对象的保存范围：page，request，session，application

2. 设置属性内容：

<jsp:setProperty property="*" name="stu"/>

1. name：表示的要操作的对象名称，与id相同

2. property：要操作的属性名称，如果为* 表示自动操作，也可以指定，例如

<jsp:setProperty property="name" name="stu"/>

表示只操作name的赋值，参数名称一定要与属性名称一致（setter）

3. 取得属性内容：

<jsp:getProperty property="name" name="stu"/>

1. name：表示的要操作的对象名称，与id相同

2. property：取得输出的属性内容（getter）

但是此时的控制柜台就输出了

构造方法执行了，对象实例化

setName被调用

setAge被调用

setSex被调用

getName被调用

getAge被调用

getSex被调用

在Servlet之中自定义反射接收

对于WEB而言，发现“<jsp:useBean>”等标签只能在JSP页面使用，但是如果是一个真正开发，一定是使用Servlet进行的，所以现在就希望编写一个与之类似的功能，可以帮助我们实现此类操作。

本程序继续使用之前的Student类与student_insert.jsp页面，先完成一个专攻Student类操作的形式代码

代码范例：建立一个Servlet程序

package com.hbsi.servlet;

import java.io.IOException;

import java.lang.reflect.Field;

import java.lang.reflect.Method;

import java.util.Enumeration;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import javax.servlet.annotation.WebServlet;

/*

by:wzq

time:2017年11月12日

*/

@WebServlet(name = "studentServlet", urlPatterns = { "/studentServlet" })

public class StudentServlet extends HttpServlet {

 private static final long serialVersionUID = 1L;

 protected void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {

 request.setCharacterEncoding("UTF-8");

 response.setCharacterEncoding("UTF-8");

 response.setContentType("text/html; charset=UTF-8");

 Class<?> cls = null;

 Object object = null;

 try {

 cls = Class.forName("com.hbsi.domain.Student");

 object = cls.getDeclaredConstructor().newInstance();//获取实例化对象

 Enumeration<String> parameterNames = request.getParameterNames();//获得全部参数名称

 //判断是否有下一个参数

 while(parameterNames.hasMoreElements()) {

 //获取下一个参数

 String parameterName = parameterNames.nextElement();

 //根据参数名得到参数值

 String parameterValue = request.getParameter(parameterName);

// System.out.println(parameterName+"　"+parameterValue);//这里会显示输出前页面中参数名以及输入的参数值

 //参数名就是对应的实体类Student中的属性名，所以根据这个参数名得到其类型

 Field field = cls.getDeclaredField(parameterName);

// System.out.println(field);

 String simpleName = field.getType().getSimpleName();

 //取得setter方法。

 Method setterMethod = cls.getMethod("set"+toUpperCaseOne(parameterName), field.getType());

 //根据类型来选择的进行转换并赋值

 switch (simpleName.toLowerCase()) {

 case "string":

 //设置值

 setterMethod.invoke(object, parameterValue);

 break;

 case "int":

 case "integer":

 //设置值

 setterMethod.invoke(object, Integer.parseInt(parameterValue));

 break;

 case "date": break;

 case "double": break;

 case "char": break;

 case "character": break;

 }

 }

 } catch (Exception e) {

 e.printStackTrace();

 }

 request.setAttribute("student", object);

 request.getRequestDispatcher("student_insert_do.jsp").forward(request, response);

 }

 //将字符串转换成大写开头的字母

 public String toUpperCaseOne(String str) {

 return str.substring(0,1).toUpperCase().concat(str.substring(1).toLowerCase());

 }

 protected void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {

 request.setCharacterEncoding("UTF-8");

 response.setCharacterEncoding("UTF-8");

 response.setContentType("text/html; charset=UTF-8");

 this.doGet(request, response);

 }

}

页面代码范例：输出数据

<h1>Name:${student.name }</h1>

<h1>Age :${student.age }</h1>

<h1>Sex :${student.sex }</h1>

我们在表单页面输入“懒蛋，20，gg”，执行结果

但是如果将我们的所有的代码都放在Servlet类中进行处理的话，实在是过于麻烦，因为类的面向对象的设计原则是不同的组件完成不同功能。下面定义一个Bean操作的工具类

代码范例：定义一个工具类以实现属性的设置

package com.hbsi.BeanTools;

import java.lang.reflect.Field;

import java.lang.reflect.Method;

import java.util.Enumeration;

import javax.servlet.ServletRequest;

import com.hbsi.stringUtils.StringTools;

/*

by:wzq

time:2017年11月12日

*/

public class BeanTools {

 /**

 * 这个方法只限制在WEB项目中使用，

 * 利用反射进行所有请求参数的设置，要求参数名称要与属性名称保持一致

 * @param obj 要操作的实例化对象

 * @param request HttpServletRequeat接口对象实例，目的是为了获得页面的输入参数

 * @throws Exception

 */

 public static void setValue(Object obj,ServletRequest request) throws Exception {

 Enumeration<String> parameterNames = request.getParameterNames();//获得全部参数名称

 //判断是否有下一个参数

 while(parameterNames.hasMoreElements()) {

 //获取下一个参数

 String parameterName = parameterNames.nextElement();

 //根据参数名得到参数值

 String parameterValue = request.getParameter(parameterName);

// System.out.println(parameterName+"　"+parameterValue);//这里会显示输出前页面中参数名以及输入的参数值

 //参数名就是对应的实体类Student中的属性名，所以根据这个参数名得到其类型

 Field field = obj.getClass().getDeclaredField(parameterName);

// System.out.println(field);

 String simpleName = field.getType().getSimpleName();

 //取得setter方法。

 Method setterMethod = obj.getClass().getMethod("set"+StringTools.toUpperCaseOne(parameterName), field.getType());

 //根据类型来选择的进行转换并赋值

 switch (simpleName.toLowerCase()) {

 case "string":

 //设置值

 setterMethod.invoke(obj, parameterValue);

 break;

 case "int":

 case "integer":

 //设置值

 setterMethod.invoke(obj, Integer.parseInt(parameterValue));

 break;

 case "date": break;

 case "double": break;

 case "char": break;

 case "character": break;

 }

 }

 }

}

上述代码中使用的StringTools代码示例：

package com.hbsi.stringUtils;

/*

by:wzq

time:2017年11月12日

*/

public class StringTools {

 //将字符串转换成大写开头的字母

 public static String toUpperCaseOne(String str) {

 return str.substring(0,1).toUpperCase().concat(str.substring(1).toLowerCase());

 }

}

现在Servlet中的代码就相当简单了，代码示例

package com.hbsi.servlet;

import java.io.IOException;

import java.lang.reflect.Field;

import java.lang.reflect.Method;

import java.util.Enumeration;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import com.hbsi.BeanTools.BeanTools;

import javax.servlet.annotation.WebServlet;

/*

by:wzq

time:2017年11月12日

*/

@WebServlet(name = "studentServlet", urlPatterns = { "/studentServlet" })

public class StudentServlet extends HttpServlet {

 private static final long serialVersionUID = 1L;

 protected void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {

 request.setCharacterEncoding("UTF-8");

 response.setCharacterEncoding("UTF-8");

 response.setContentType("text/html; charset=UTF-8");

 try {

 Class<?> cls = cls = Class.forName("com.hbsi.domain.Student");

 Object object = cls.getDeclaredConstructor().newInstance();//获取实例化对象

 BeanTools.setValue(object, request);

 request.setAttribute("student", object);

 request.getRequestDispatcher("student_insert_do.jsp").forward(request, response);

 } catch (Exception e) {

 e.printStackTrace();

 }

 }

 protected void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {

 request.setCharacterEncoding("UTF-8");

 response.setCharacterEncoding("UTF-8");

 response.setContentType("text/html; charset=UTF-8");

 this.doGet(request, response);

 }

}

代码执行，表单输入“懒蛋，25，gr”

只要存在这样一个组件，那么在以后的开发里面就再也不用去编写接收数据，转型，设置属性等操作，但是整个操作的核心是一定要准备好实例化对象

除了针对于属性的操作可以通过反射简化代码之外，那么下面也可以运用反射进行解决Servlet重复的问题，几乎所有的Servlet都会存在以下的设计问题：

1. 需要接受的一个参数来区分操作类型，

2. 接收的状态参数（status）必须手工编写if else以区分执行那个方法

3. 到处充满了重复设置，sg，path属性的操作以及跳转代码。

解决操作状态的问题

1. 操作状态如果不接收，那么是无法进行操作的区分的，但是每次接受操作状态的时候都会感觉到无奈。

状态例如：localhost:8080/tes/studentServlet/update 此时就要求的是更新操作

2. 在HttpServletRequest接口中定义了一个取得请求路径的方法： request.getRequestURI()

代码示例：取得状态码

package com.hbsi.servlet;

import java.io.IOException;

import java.lang.reflect.Field;

import java.lang.reflect.Method;

import java.util.Enumeration;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import com.hbsi.BeanTools.BeanTools;

import javax.servlet.annotation.WebServlet;

/*

by:wzq

time:2017年11月12日

*/

@WebServlet(name = "employeeServlet", urlPatterns = { "/EmployeeServlet/*" })

public class EmployeeServlet extends HttpServlet {

 private static final long serialVersionUID = 1L;

 protected void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {

 String requestURI = request.getRequestURI();

 System.out.println(requestURI);//请求全路径

 int lastIndexOf = requestURI.lastIndexOf("/");//取得最后一个/的位置

 String substring = requestURI.substring(lastIndexOf+1);

 System.out.println(substring);

 }

 protected void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {

 this.doGet(request, response);

 }

}

请求路径：http://localhost:8080/tes/EmployeeServlet/update

执行结果：update

对于所有的操作方法上都可以发现，操作的状态就是方法名称

代码示例：解决代码调用

package com.hbsi.servlet;

import java.io.IOException;

import java.lang.reflect.Method;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import javax.servlet.annotation.WebServlet;

/*

by:wzq

time:2017年11月13日

*/

@WebServlet(name = "dispatchaerServlet", urlPatterns = { "/DispatchaerServlet/*" })

public class DispatchaerServlet extends HttpServlet {

private static final long serialVersionUID = 1L;

protected void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {

String requestURI = request.getRequestURI();

//取得最后一个/的位置

int lastIndexOf = requestURI.lastIndexOf("/");

//状态信息

String status = requestURI.substring(lastIndexOf+1);

System.out.println(status);//输出状态信息

//得到本类的所有方法

Method[] declaredMethods = this.getClass().getDeclaredMethods();

//循环判断状态信息与本类的方法名是否一致

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

if(declaredMethods[i].getName().equals(status)) {

//如果一直获得参数类型

Class<?>[] parameterTypes = declaredMethods[i].getParameterTypes();

try {

//根据参数类型得到其方法

Method method = this.getClass().getMethod(status, parameterTypes);

//调用方法

method.invoke(this, request,response);

} catch (Exception e) {

e.printStackTrace();

}

}

}

}

public void insert(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {

System.out.println("执行插入方法");

}

public void delete(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {

System.out.println("执行删除方法");

}

public void update(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {

System.out.println("执行更新方法");

}

protected void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {

this.doGet(request, response);

}

}

请求路径：http://localhost:8080/tes/DispatchaerServlet/insert

执行结果：insert 执行插入方法

在上述代码中method.invoke(this, request,response);需要区分参数是比较麻烦的，而且必须是需要匹配好后才可以调用

以上的代码调用严格来讲算是一种习惯，因为各个方法里面需要有request，response等对象但是也同时感觉到，麻烦程度很高，比如需要知道参数的个数。

如果不想做参数的判断，如果说现在像insert(),update()等操作，那些地方可能使用到request或者response，接收参数，跳转，

代码优化：

package com.hbsi.servlet;

import java.io.IOException;

import java.lang.reflect.InvocationTargetException;

import java.lang.reflect.Method;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import javax.servlet.annotation.WebServlet;

/*

by:wzq

time:2017年11月13日

*/

@WebServlet(name = "dispatchaerServlet", urlPatterns = { "/DispatchaerServlet/*" })

public class DispatchaerServlet extends HttpServlet {

private static final long serialVersionUID = 1L;

protected void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {

String uri = "/errors.jsp";

String requestURI = request.getRequestURI();

//取得最后一个/的位置

int lastIndexOf = requestURI.lastIndexOf("/");

//状态信息

String status = requestURI.substring(lastIndexOf+1);

try {

Method method = this.getClass().getMethod(status);

uri = method.invoke(this).toString();

} catch (Exception e) {

e.printStackTrace();

}

request.getRequestDispatcher(uri).forward(request, response);

}

public String insert(){

System.out.println("执行插入方法");

return "/insert.jsp";

}

public String delete() {

System.out.println("执行删除方法");

return "/delete.jsp";

}

public String update() {

System.out.println("执行更新方法");

return "/update.jsp";

}

protected void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {

this.doGet(request, response);

}

}

执行结果：执行插入方法

此时Servlet已经可以反射调用，而且也可以反射将表单的参数设置给属性。

总结：关于反射设置数据内容的情况

代码示例：定义三个类，Emp，Dept，Company，三个类相关联

Emp> Dept > Company

代码实现功能：可以深层的为对象的属性赋值，

EMP属性:

private Integer empid;

private String empname;

private Dept dept = new Dept();

Dept属性:

private Integer deptid;

private String deptname;

private Company company = new Company();

Company属性:

private Integer companyid;

private String companyname;

工具类StringFirstUPTools：

//作用就是将制定字符串的首字母大写处理

public static String stringFirstUP(String str) {

return str.substring(0, 1).toUpperCase()+str.substring(1,str.length());

}

核心代码实现：注意不适用于自身赋值

package com.hbsi.servlet;

import java.lang.reflect.Field;

import java.lang.reflect.Method;

import com.hbsi.domain.Emp;

/*

by:wzq

time:2017年11月18日

*/

public class Servlet {

//emp属性操作需要当前类对象完成

//emp.dept属性需要由emp类对象完成

private String requestParamName = "emp.dept.deptid";//模拟多级赋值的操作的参数

private String value = "6666";

private Emp emp = new Emp();//必须有实例化对象

public Emp getEmp() {

return emp;

}

public void handleParam(String paramName,String value) throws Exception {

String[] split = paramName.split("\\.");

Object currentObj = this;

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

//根据拆分后的字符串得到相应的getter方法

Method method = currentObj.getClass().getMethod("get"+StringFirstUPTools.stringFirstUP(split[i]));

if(i<split.length-1) {//判断是否为最后一个对象而非属性

currentObj = method.invoke(currentObj);//将得到的下一个对象赋值到currentObj

}

}

//根据属性名称得到属性对象

Field declaredField = currentObj.getClass().getDeclaredField(split[split.length-1]);

Class<?> type = declaredField.getType();//属性类型

String typeName = type.getSimpleName();//属性类型简单名称

//根据属性名及类型得到对应的setter方法

Method declaredMethod = currentObj.getClass().getDeclaredMethod("set"+StringFirstUPTools.stringFirstUP(split[split.length-1]), type);

//根据类型来选择的进行转换并赋值

switch (typeName.toLowerCase()) {

case "string": declaredMethod.invoke(currentObj, String.valueOf(value)); break;

case "int":

case "integer": declaredMethod.invoke(currentObj, Integer.parseInt(value)); break;

case "double": declaredMethod.invoke(currentObj, Double.valueOf(value)); break;

}

}

public void get() {//模拟请求

try {

this.handleParam(this.requestParamName,this.value);

} catch (Exception e) {

e.printStackTrace();

}

//验证

Integer companyid = this.getEmp().getDept().getDeptid();

System.out.println(companyid);

}

public static void main(String[] args) {

new Servlet().get();

}

}

执行结果： 6666

使用此类操作可以无限制进行数据的赋值，排除自关联的情况

ClassLoader类

当使用java命令解释程序的时候，会自动根据CLASSPATH加载所需要的类文件，而用户现在要也可以编写自己的类加载器。

在Class类里面默认定义有专门的取得一个类的类加载器的方法

取得类加载器：public ClassLoader getClassLoader() 返回类的类加载器。

public class ClassLoderDemo {

public static void main(String[] args) {

ClassLoderDemo classLoderDemo = new ClassLoderDemo();

System.out.println(classLoderDemo.getClass().getClassLoader());

System.out.println(classLoderDemo.getClass().getClassLoader().getParent());

System.out.println(classLoderDemo.getClass().getClassLoader().getParent().getParent());

}

}

执行结果

jdk.internal.loader.ClassLoaders$AppClassLoader@7960847b //系统类加载器

jdk.internal.loader.ClassLoaders$PlatformClassLoader@2f333739 //系统类加载器的父类加载器

null

自己也可以自定义一个类加载器，只需要继承 ClassLoader即可，此类定义如下

public abstract class ClassLoader extends Object 类加载器是负责加载类的对象。

ClassLoader的子类只需要重写loadClass方法就可以进行类加载的实现

代码示例：做一个默认的类加载器

public class MyClassLoader extends ClassLoader{

@Override

public Class<?> loadClass(String arg0) throws ClassNotFoundException {

return super.loadClass(arg0);//直接调用父类的loadClass()方法

}

public static void main(String[] args) throws Exception {

MyClassLoader myClassLoader = new MyClassLoader();

Class<?> loadClass = myClassLoader.loadClass("java.util.Date");//与Class.forName()作用几乎一样

Object newInstance = loadClass.getDeclaredConstructor().newInstance();

System.out.println(newInstance);//Sun Nov 19 11:51:29 CST 2017

}

}

上述程序只是继承并直接是调用了父类中的方法，与使用Class.forName()作用几乎一样，因为都是默认实现，下面使用自定义的类加载器加载指定文件

代码示例：创建一个Student类，并且把Student编译后的class文件复制到D盘根目录下，

package com.hbsi.domain;

public class Student {

public Student() {

System.out.println("student 实例化");

}

@Override

public String toString() {

return "Student 学生信息 toString()";

}

}

实现自定义类加载器，---加载文件数据

package com.hbsi.servlet;

import java.io.ByteArrayOutputStream;

import java.io.File;

import java.io.FileInputStream;

import java.io.InputStream;

public class ClassLoderDemo extends ClassLoader{

public static void main(String[] args) {

try {

ClassLoderDemo classLoderDemo = new ClassLoderDemo();

classLoderDemo.loadClassFile("com.hbsi.domain.Student");//参数必须是包点类名

} catch (Exception e) {

e.printStackTrace();

}

}

public void loadClassFile(String className) {

try {

byte[] loadFile = this.loadFile(className);

//defineClass() 将字节数组转换为类别 Class的实例

Class<?> defineClass = super.defineClass(className, loadFile, 0, loadFile.length);

Object newInstance = defineClass.getDeclaredConstructor().newInstance();//实例化

System.out.println(newInstance);//输出调用toString

} catch (Exception e) {

e.printStackTrace();

}

}

public byte[] loadFile(String className) throws Exception{

String[] split = className.split("\\.");//拆分

String name = split[split.length-1];//取的Class类名

File file = new File("D:/"+name+".class");//拼接路径

//内存输出流

ByteArrayOutputStream arrayOutputStream = new ByteArrayOutputStream();

//字节流

InputStream inputStream = new FileInputStream(file);

byte date[] = new byte[1024];//缓冲区

int len = 0;

while((len = inputStream.read(date))!=-1) {

arrayOutputStream.write(date, 0, len);

}

//将内存中的数据取出

byte[] byteArray = arrayOutputStream.toByteArray();

arrayOutputStream.close();

inputStream.close();

return byteArray;

}

}

执行结果： student 实例化

Student 学生信息 toString()

在编写自定义类加载器的时候有如下要求

1. 不要重写loadClass方法，因为此方法会使会使用部分默认系统类加载器

2. 如果是手工加载方式，则可以使用方法进行转换：

1. protected final Class<?> defineClass(String name, byte[] b,int off,int len) throws ClassFormatError 将字节数组转换为类别Class的实例。

此时的类加载的方式可能发生变化，那么就可以将程序继续扩大，直接利用HTTP协议加载，我们将Student.class文件拷贝到WEB目录下，这样就成为了WEB资源，如果要访问，必须基于HTTP协议完成。如果进行网络加载，就必须使用URL类，在java.net包中，如下代码，

package com.hbsi.BeanTools;

import java.io.ByteArrayOutputStream;

import java.io.InputStream;

import java.net.URL;

import java.net.URLConnection;

public class ClassLoderDemo extends ClassLoader{

public static void main(String[] args) {

try {

ClassLoderDemo classLoderDemo = new ClassLoderDemo();

classLoderDemo.loadClassFile("com.hbsi.domain.Student");//参数必须是包点类名

} catch (Exception e) {

e.printStackTrace();

}

}

public void loadClassFile(String className) {

try {

byte[] loadFile = this.loadFile(className);

//defineClass() 将字节数组转换为类别 Class的实例

Class<?> defineClass = super.defineClass(className, loadFile, 0, loadFile.length);

Object newInstance = defineClass.getDeclaredConstructor().newInstance();//实例化

System.out.println(newInstance);//输出调用toString

} catch (Exception e) {

e.printStackTrace();

}

}

public byte[] loadFile(String className) throws Exception{

String[] split = className.split("\\.");//拆分

String name = split[split.length-1];//取的Class类名

URL url = new URL("http://localhost:8080/tes/"+name+".class");

URLConnection openConnection = url.openConnection();

//内存输出流

ByteArrayOutputStream arrayOutputStream = new ByteArrayOutputStream();

//字节流

InputStream inputStream = openConnection.getInputStream();

byte date[] = new byte[1024];//缓冲区

int len = 0;

while((len = inputStream.read(date))!=-1) {

arrayOutputStream.write(date, 0, len);

}

//将内存中的数据取出

byte[] byteArray = arrayOutputStream.toByteArray();

arrayOutputStream.close();

inputStream.close();

return byteArray;

}

}

以及Student.class的存放目录

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" alt="" />

执行结果：

student 实例化

Student 学生信息 toString()

在进行类加载的过程之中存在一种概念 -- 双亲加载：如果是系统类则会由系统的类加载器进行加载，例如如果现在加载的是java.lang.String,那么这个类会在程序运行时自动完成加载，而后如果用户再以同样的名称加载了自定义的java.lang.String，那么在系统之中就会做出一个检测，如果检测出了一个问题，则无法加载，会出现错误提示。

巴特西

java--分析简单java类与反射的联系

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