Fun论设计模式之2：代理模式（Proxy Pattern）与华为云API设计之一

　　今天学习到了一个新的设计模式：代理模式。介绍借鉴了runoob的：

　　意图：为其他对象提供一种代理以控制对这个对象的访问。

　　主要解决：在直接访问对象时带来的问题，比如说：要访问的对象在远程的机器上。在面向对象系统中，有些对象由于某些原因（比如对象创建开销很大，或者某些操作需要安全控制，或者需要进程外的访问），直接访问会给使用者或者系统结构带来很多麻烦，我们可以在访问此对象时加上一个对此对象的访问层。

　　何时使用：想在访问一个类时做一些控制。

　　如何解决：增加中间层。

　　关键代码：实现与被代理类组合。

　　访问一个类是做一些控制，增加中间层，这种情况一般都出现在账号密码验证、令牌验证之类，需要检验或修改部分信息，但对业务结构没有改变的情况。

　　Struts2的filter，还有SpringMVC的interceptor，以及Java的注解，本质上都是代理模式。

　　这里有一个使用了代理模式的例子：

　　之前为了给系统对接华为云API，设计了一套restful API的封装类，有多种封装类型，VPCUtil（虚拟私有云），ECSUtil（云服务器），SecurityGroupUtil（安全组），PublicIPUtil（公开IP），这几种请求不同的业务，但是都有一个相同点：操作之前要先登录，使用IAMUtil（身份验证）里的封装函数发送账号密码，返回有效期为24小时的token，这个token拿去请求其他业务（何时使用）。

　　图1. 华为云API模块操作流程图

　　每次开启服务器时都要获取一次token，并且每次请求华为云都要检查token是否过期，过期则重新更新token。

　　如果这个操作是写在业务Util里面，每次操作都要在对象函数里面执行一次，像VPCUtil：

import java.util.UUID;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

public class VPCUtil{
    
    private String username;
    
    private String password;
    
    private String token;
    
    private String projectId;
    
    private long overDate;
    
    public IAMUtil(){
    } 
    
    public IAMUtil(String username, String password){
        this.username = username;
        this.password = password;
        TokenAndProject tap = new IAMUtil().getToken(username,password);
        this.overDate = System.currentTimeMillis() + 23*60*60*1000;
        this.token = tap.getToken();
        this.projectId = tap.getProjectId();
    }
    
    /**
     * 
     * @Title createVPC
     * @Description 创建虚拟私有云
     * @param idx
     * @return vpc_id 虚拟私有云的ID
     */
    public String createVPC(int idx, String name_prefix) {
        this.checkAccount();
        JSONObject resjo = null;
        String res = RequestUtil.requestsPost("https://vpc.cn-south-1.myhuaweicloud.com/v1/" + projectId + "/vpcs","{"vpc": {"name": "" + name_prefix + "-" + (1+idx) + "","cidr": "192.168.0.0/16"}}",token);
        String vpc_id = "";
        try {
            resjo = new JSONObject(res);
            vpc_id = resjo.getJSONObject("vpc").getString("id");
        } catch (JSONException e) {
            System.out.println(res);
            e.printStackTrace();
        }finally {
        }
        return vpc_id;
    }
    
    /**
     * 
     * @Title createVPC
     * @Description 创建虚拟私有云的子网
     * @param subNo 192.168.x.y 里面的x
     * @return vpc_id 虚拟私有云的ID
     */
    public NetWorkIds createSubnet(int idx, String vpc_id, int subNo, String name_prefix) {
        this.checkAccount();
        JSONObject resjo = null;
        String res = RequestUtil.requestsPost("https://vpc.cn-south-1.myhuaweicloud.com/v1/" + projectId + "/subnets",
                "{"subnet": {"name": "" + name_prefix + "-" + (subNo == 10 ? "manager" : "service") + "-" + (1+idx) + "","cidr": "192.168." + subNo + ".0/24","gateway_ip": "192.168." + subNo + ".254","vpc_id": "" + vpc_id + ""}}",token);
        String netId = "";
        String subnetId = "";
        try {
            resjo = new JSONObject(res);
            netId = resjo.getJSONObject("subnet").getString("id");
            subnetId = resjo.getJSONObject("subnet").getString("neutron_subnet_id");
        } catch (JSONException e) {
            System.out.println(res);
            e.printStackTrace();
        }finally {
        }
        return new NetWorkIds(netId,subnetId);
    }
    
    public NetWorkIds createSubnetFilter(int idx, String vpc_id, int subNo, String name_prefix) {
        this.checkAccount();
        NetWorkIds nids = createSubnet(idx, vpc_id, subNo, name_prefix);
        while(true) {
            String portsres = getPorts(nids.getNetId(), true);
            JSONArray ports = null;
            JSONArray fixed_ips = null;
            try {
                ports = new JSONArray(portsres);
                if(ports.length() <= 0)continue;
                fixed_ips = ports.getJSONObject(0).getJSONArray("fixed_ips");
                if(fixed_ips.length() <= 0)continue;
                String ip_address = fixed_ips.getJSONObject(0).getString("ip_address");
                int ip4 = Integer.parseInt(ip_address.split("\.")[3]);
                System.out.println("I get the address : " + ip_address);
                if((ip4 >= 1 && ip4 <= 4) || (ip4 >= 100 && ip4 <= 103)){
                    nids = new VPCUtil().createSubnet(token, projectId, idx, vpc_id, subNo, name_prefix);
                }else {
                    break;
                }
            } catch (JSONException e) {
                System.out.println(portsres);
                e.printStackTrace();
            }
        }
        
        return nids;
    }
    
    public String createVirtualIP(String net_id, String subnet_id, String ip) {
        this.checkAccount();
        String res = RequestUtil.requestsPost("https://vpc.cn-south-1.myhuaweicloud.com/v2.0/ports",
                "{"port": {"network_id": "" + net_id + "","device_owner": "neutron:VIP_PORT","name": "" + UUID.randomUUID().toString() + "","fixed_ips": [{"subnet_id": "" + subnet_id + "", "ip_address": "" + ip + ""}]}}", token);
        String new_port_id = "";
        try {
            new_port_id = new JSONObject(res).getJSONObject("port").getString("id");
        } catch (JSONException e) {
            System.out.println(res);
            e.printStackTrace();
        }
        return new_port_id;
    }    
    
    public void createVirtualIPport(String port_id, String ip1, String ip2) {
        this.checkAccount();
        RequestUtil.requestsPut("https://vpc.cn-south-1.myhuaweicloud.com/v2.0/ports/" + port_id,
                "{"port": {"allowed_address_pairs": [{"ip_address":"" + ip1 + ""},{"ip_address":"" + ip2 + ""}]}}", token);
    }
    
    /**
     * 
     * @Title getVPCs
     * @Description 获取虚拟私有云列表
     * @return vpcsInJSON 虚拟私有云列表的JOSN格式字符串
     */
    public String getVPCs() {
        this.checkAccount();
        String res = RequestUtil.requestsGet("https://vpc.cn-south-1.myhuaweicloud.com/v1/" + projectId + "/vpcs", token);
        try {
            JSONObject resjo = new JSONObject(res);
            JSONArray vpcs = resjo.getJSONArray("vpcs");
            res = vpcs.toString();
        } catch (JSONException e) {
            System.out.println(res);
            e.printStackTrace();
        }
        return res;
    }
    
    public String getSubnets(String vpc_id) {
        this.checkAccount();
        String res = RequestUtil.requestsGet("https://vpc.cn-south-1.myhuaweicloud.com/v1/" + projectId + "/subnets?project_id" + projectId + (vpc_id == null ? "" : "&vpc_id=" + vpc_id), token);
        try {
            JSONObject resjo = new JSONObject(res);
            JSONArray vpcs = resjo.getJSONArray("subnets");
            res = vpcs.toString();
        } catch (JSONException e) {
            System.out.println(res);
            e.printStackTrace();
        }
        return res;
    }
    
    public String getPorts(String network_id) {
        this.checkAccount();
        return getPorts(network_id, false);
    }
    
    public String getPorts(String network_id, boolean isDHCP) {
        this.checkAccount();
        String res = RequestUtil.requestsGet("https://vpc.cn-south-1.myhuaweicloud.com/v2.0/ports?project_id=" + projectId + (network_id == null ? "" : "&network_id=" + network_id) + (isDHCP ? "&device_owner=network:dhcp" : ""), token);
        try {
            JSONObject resjo = new JSONObject(res);
            JSONArray vpcs = resjo.getJSONArray("ports");
            res = vpcs.toString();
        } catch (JSONException e) {
            System.out.println(res);
            e.printStackTrace();
        }
        return res;
    }
    
    public String deletePort(String token, String port_id) {
        this.checkAccount();
        System.out.println("deletePort start " + port_id);
        String res = RequestUtil.requestsDelete("https://vpc.cn-south-1.myhuaweicloud.com/v2.0/ports/" + port_id, token);
        System.out.println(res);
        System.out.println("deletePort end");
        return res;
    }
    
    public String deleteSubnet(String vpc_id, String network_id) {
        this.checkAccount();
        System.out.println("deleteSubnet start " + network_id);
        String res = RequestUtil.requestsDelete("https://vpc.cn-south-1.myhuaweicloud.com/v1/" + projectId + "/vpcs/"+ vpc_id +"/subnets/" + network_id, token);
        System.out.println(res);
        System.out.println("deleteSubnet end");
        return res;
    }
    
    public String deleteVPC(String vpc_id) {
        this.checkAccount();
        String res = RequestUtil.requestsDelete("https://vpc.cn-south-1.myhuaweicloud.com/v1/" + projectId + "/vpcs/" + vpc_id, token);
        System.out.println(res);
        return res;
    }
    
    private void checkAccount(){
        if(tap == null || System.currentTimeMillis() > overDate) {
            tap = new IAMUtil().getToken(this.username,this.password);
            this.token = tap.getToken();
            this.projectId = tap.getProjectId();
            this.overDate = System.currentTimeMillis() + 23*60*60*1000;
        }
    }
    
}

class NetWorkIds{
    String netId;
    String subnetId;
    public NetWorkIds(String netId, String subnetId) {
        super();
        this.netId = netId;
        this.subnetId = subnetId;
    }
    
    public String getNetId() {return netId;}
    public String getSubNetId() {return subnetId;}
}

　　这里，每个操作前面都要执行checkAccount这个函数。如果这个业务要经常添加功能的话，每个函数都要在这里添加这个前置动作，很容易因为某些原因，把代码写错，也不利于维护。

　　可以给这上面的所有代码做个代理，并且把username和password、token、projectId的可见性设置为protected，为后面的变量访问做准备。

　　直接把函数写在代理的注入过程里面（如何解决），就可以在不用写前置代码的前提下执行token校验了；外部类调用代理过的对象。为了让cglib能代理成功，需要声明无参构造函数：

import java.util.UUID;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

public class VPCUtil{
    
    protected String username;
    
    protected String password;
    
    protected String token;
    
    protected String projectId;
    
    protected long overDate;
    
    public IAMUtil(){
    } 
    
    public IAMUtil(String username, String password){
        this.username = username;
        this.password = password;
        TokenAndProject tap = new IAMUtil().getToken(username,password);
        this.overDate = System.currentTimeMillis() + 23*60*60*1000;
        this.token = tap.getToken();
        this.projectId = tap.getProjectId();
    }
    
    /**
     * 
     * @Title createVPC
     * @Description 创建虚拟私有云
     * @param idx
     * @return vpc_id 虚拟私有云的ID
     */
    public String createVPC(int idx, String name_prefix) {
        this.checkAccount();
        JSONObject resjo = null;
        String res = RequestUtil.requestsPost("https://vpc.cn-south-1.myhuaweicloud.com/v1/" + projectId + "/vpcs","{"vpc": {"name": "" + name_prefix + "-" + (1+idx) + "","cidr": "192.168.0.0/16"}}",token);
        String vpc_id = "";
        try {
            resjo = new JSONObject(res);
            vpc_id = resjo.getJSONObject("vpc").getString("id");
        } catch (JSONException e) {
            System.out.println(res);
            e.printStackTrace();
        }finally {
        }
        return vpc_id;
    }
    
    /**
     * 
     * @Title createVPC
     * @Description 创建虚拟私有云的子网
     * @param subNo 192.168.x.y 里面的x
     * @return vpc_id 虚拟私有云的ID
     */
    public NetWorkIds createSubnet(int idx, String vpc_id, int subNo, String name_prefix) {
        this.checkAccount();
        JSONObject resjo = null;
        String res = RequestUtil.requestsPost("https://vpc.cn-south-1.myhuaweicloud.com/v1/" + projectId + "/subnets",
                "{"subnet": {"name": "" + name_prefix + "-" + (subNo == 10 ? "manager" : "service") + "-" + (1+idx) + "","cidr": "192.168." + subNo + ".0/24","gateway_ip": "192.168." + subNo + ".254","vpc_id": "" + vpc_id + ""}}",token);
        String netId = "";
        String subnetId = "";
        try {
            resjo = new JSONObject(res);
            netId = resjo.getJSONObject("subnet").getString("id");
            subnetId = resjo.getJSONObject("subnet").getString("neutron_subnet_id");
        } catch (JSONException e) {
            System.out.println(res);
            e.printStackTrace();
        }finally {
        }
        return new NetWorkIds(netId,subnetId);
    }
    
    public NetWorkIds createSubnetFilter(int idx, String vpc_id, int subNo, String name_prefix) {
        this.checkAccount();
        NetWorkIds nids = createSubnet(idx, vpc_id, subNo, name_prefix);
        while(true) {
            String portsres = getPorts(nids.getNetId(), true);
            JSONArray ports = null;
            JSONArray fixed_ips = null;
            try {
                ports = new JSONArray(portsres);
                if(ports.length() <= 0)continue;
                fixed_ips = ports.getJSONObject(0).getJSONArray("fixed_ips");
                if(fixed_ips.length() <= 0)continue;
                String ip_address = fixed_ips.getJSONObject(0).getString("ip_address");
                int ip4 = Integer.parseInt(ip_address.split("\.")[3]);
                System.out.println("I get the address : " + ip_address);
                if((ip4 >= 1 && ip4 <= 4) || (ip4 >= 100 && ip4 <= 103)){
                    nids = new VPCUtil().createSubnet(token, projectId, idx, vpc_id, subNo, name_prefix);
                }else {
                    break;
                }
            } catch (JSONException e) {
                System.out.println(portsres);
                e.printStackTrace();
            }
        }
        
        return nids;
    }
    
    public String createVirtualIP(String net_id, String subnet_id, String ip) {
        this.checkAccount();
        String res = RequestUtil.requestsPost("https://vpc.cn-south-1.myhuaweicloud.com/v2.0/ports",
                "{"port": {"network_id": "" + net_id + "","device_owner": "neutron:VIP_PORT","name": "" + UUID.randomUUID().toString() + "","fixed_ips": [{"subnet_id": "" + subnet_id + "", "ip_address": "" + ip + ""}]}}", token);
        String new_port_id = "";
        try {
            new_port_id = new JSONObject(res).getJSONObject("port").getString("id");
        } catch (JSONException e) {
            System.out.println(res);
            e.printStackTrace();
        }
        return new_port_id;
    }    
    
    public void createVirtualIPport(String port_id, String ip1, String ip2) {
        this.checkAccount();
        RequestUtil.requestsPut("https://vpc.cn-south-1.myhuaweicloud.com/v2.0/ports/" + port_id,
                "{"port": {"allowed_address_pairs": [{"ip_address":"" + ip1 + ""},{"ip_address":"" + ip2 + ""}]}}", token);
    }
    
    /**
     * 
     * @Title getVPCs
     * @Description 获取虚拟私有云列表
     * @return vpcsInJSON 虚拟私有云列表的JOSN格式字符串
     */
    public String getVPCs() {
        this.checkAccount();
        String res = RequestUtil.requestsGet("https://vpc.cn-south-1.myhuaweicloud.com/v1/" + projectId + "/vpcs", token);
        try {
            JSONObject resjo = new JSONObject(res);
            JSONArray vpcs = resjo.getJSONArray("vpcs");
            res = vpcs.toString();
        } catch (JSONException e) {
            System.out.println(res);
            e.printStackTrace();
        }
        return res;
    }
    
    public String getSubnets(String vpc_id) {
        this.checkAccount();
        String res = RequestUtil.requestsGet("https://vpc.cn-south-1.myhuaweicloud.com/v1/" + projectId + "/subnets?project_id" + projectId + (vpc_id == null ? "" : "&vpc_id=" + vpc_id), token);
        try {
            JSONObject resjo = new JSONObject(res);
            JSONArray vpcs = resjo.getJSONArray("subnets");
            res = vpcs.toString();
        } catch (JSONException e) {
            System.out.println(res);
            e.printStackTrace();
        }
        return res;
    }
    
    public String getPorts(String network_id) {
        this.checkAccount();
        return getPorts(network_id, false);
    }
    
    public String getPorts(String network_id, boolean isDHCP) {
        this.checkAccount();
        String res = RequestUtil.requestsGet("https://vpc.cn-south-1.myhuaweicloud.com/v2.0/ports?project_id=" + projectId + (network_id == null ? "" : "&network_id=" + network_id) + (isDHCP ? "&device_owner=network:dhcp" : ""), token);
        try {
            JSONObject resjo = new JSONObject(res);
            JSONArray vpcs = resjo.getJSONArray("ports");
            res = vpcs.toString();
        } catch (JSONException e) {
            System.out.println(res);
            e.printStackTrace();
        }
        return res;
    }
    
    public String deletePort(String token, String port_id) {
        this.checkAccount();
        System.out.println("deletePort start " + port_id);
        String res = RequestUtil.requestsDelete("https://vpc.cn-south-1.myhuaweicloud.com/v2.0/ports/" + port_id, token);
        System.out.println(res);
        System.out.println("deletePort end");
        return res;
    }
    
    public String deleteSubnet(String vpc_id, String network_id) {
        this.checkAccount();
        System.out.println("deleteSubnet start " + network_id);
        String res = RequestUtil.requestsDelete("https://vpc.cn-south-1.myhuaweicloud.com/v1/" + projectId + "/vpcs/"+ vpc_id +"/subnets/" + network_id, token);
        System.out.println(res);
        System.out.println("deleteSubnet end");
        return res;
    }
    
    public String deleteVPC(String vpc_id) {
        this.checkAccount();
        String res = RequestUtil.requestsDelete("https://vpc.cn-south-1.myhuaweicloud.com/v1/" + projectId + "/vpcs/" + vpc_id, token);
        System.out.println(res);
        return res;
    }
    
    private void checkAccount(){
        if(tap == null || System.currentTimeMillis() > overDate) {
            tap = new IAMUtil().getToken(this.username,this.password);
            this.token = tap.getToken();
            this.projectId = tap.getProjectId();
            this.overDate = System.currentTimeMillis() + 23*60*60*1000;
        }
    }
    
}

class NetWorkIds{
    String netId;
    String subnetId;
    public NetWorkIds(String netId, String subnetId) {
        super();
        this.netId = netId;
        this.subnetId = subnetId;
    }
    
    public String getNetId() {return netId;}
    public String getSubNetId() {return subnetId;}
}

　　代理这个Util的类：

import java.lang.reflect.Method;

import org.springframework.cglib.proxy.Enhancer;
import org.springframework.cglib.proxy.MethodInterceptor;
import org.springframework.cglib.proxy.MethodProxy;

public class TokenProxy {
    
    private VPCUtil VPCProxy = null;
    
    public TokenProxy(String username, String password) {
        Enhancer enhancer = new Enhancer();
        enhancer.setSuperclass(VPCUtil.class);
        // 设置enhancer的回调对象
        enhancer.setCallback(new MethodInterceptor() {
            private TokenAndProject tap = null;
            private long overDate = 0;
            @Override
            public Object intercept(Object sub, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable {
                ((VPCUtil)sub).checkAccount();
                Object res = methodProxy.invokeSuper(sub, objects);
                return res;
            }
        });
        this.VPCProxy= (VPCUtil)enhancer.create();
    }
    
    public VPCUtil getVPCProxy() {
        return this.VPCProxy;
    }

}

　　但是如果运行这个类的函数，会出现StackOverFlowError错误：

Exception in thread "main" java.lang.StackOverflowError
	at zhyx_cloud.VPCUtil$$EnhancerByCGLIB$$a10b0367.checkAccount(<generated>)
	at zhyx_cloud.TokenProxy$1.intercept(TokenProxy.java:22)
	at zhyx_cloud.VPCUtil$$EnhancerByCGLIB$$a10b0367.checkAccount(<generated>)
	at zhyx_cloud.TokenProxy$1.intercept(TokenProxy.java:22)
	at zhyx_cloud.VPCUtil$$EnhancerByCGLIB$$a10b0367.checkAccount(<generated>)
	at zhyx_cloud.TokenProxy$1.intercept(TokenProxy.java:22)
	at zhyx_cloud.VPCUtil$$EnhancerByCGLIB$$a10b0367.checkAccount(<generated>)
	at zhyx_cloud.TokenProxy$1.intercept(TokenProxy.java:22)
	at zhyx_cloud.VPCUtil$$EnhancerByCGLIB$$a10b0367.checkAccount(<generated>)
	at zhyx_cloud.TokenProxy$1.intercept(TokenProxy.java:22)

　　问题出现在哪呢？实际上cglib代理这个函数时，传进来的第一参数也是经过代理的，执行这个对象的函数的话，这个函数会先进入代理注入环节，然后注入函数里面又会调用到这个函数，这就造成了死循环递归。

　　就是说，在无法保证递归终点的情况下，注入函数里面不能调用被代理对象本身的函数，那就只能把整个函数都抄过来了（关键代码）。

import java.lang.reflect.Method;

import org.springframework.cglib.proxy.Enhancer;
import org.springframework.cglib.proxy.MethodInterceptor;
import org.springframework.cglib.proxy.MethodProxy;

public class TokenProxy {
    
    private VPCUtil VPCProxy = null;
    
    public TokenProxy(String username, String password) {
        Enhancer enhancer = new Enhancer();
        enhancer.setSuperclass(VPCUtil.class);
        // 设置enhancer的回调对象
        enhancer.setCallback(new MethodInterceptor() {
            @Override
            public Object intercept(Object sub, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable {
                if(tap == null || System.currentTimeMillis() > overDate) {
                    TokenAndProject tap = new IAMUtil().getToken(this.username,this.password);
                    VPCUtil myproxy = (VPCUtil)sub;
                    myproxy.token = tap.getToken();
                    myproxy.projectId = tap.getProjectId();
                    myproxy.overDate = System.currentTimeMillis() + 23*60*60*1000;
                }
                Object res = methodProxy.invokeSuper(sub, objects);
                return res;
            }
        });
        this.VPCProxy= (VPCUtil)enhancer.create();
    }
    
    public VPCUtil getVPCProxy() {
        return this.VPCProxy;
    }

}

　　这里，没有对被代理对象的函数调用，没有循环注入的问题；同时也实现了修改内部属性的功能，使功能照常进行。

　　这里违反了DRY（don't repeat yourself）规则，但是相对来说也没啥更好的方法；这个方法的代码量和出错率还是较低的，并且运行效果与原先代码相当。

 图2. 用0.2版本TokenProxy代理之后，华为云API模块操作流程图

　　这种方法还是有一些优化空间，像图2所示，其他几个模块也要用这个，可以把这4个模块整合起来代理，这样优化级别就是模块等级了。

　　优点： 1、职责清晰。 2、高扩展性。 3、智能化。

　　缺点： 1、由于在客户端和真实主题之间增加了代理对象，因此有些类型的代理模式可能会造成请求的处理速度变慢。（Java要实现代理，就必须使用反射，这中间会涉及到类的加载，类在cglib中的字节码处理，运行时间较长）

　　2、实现代理模式需要额外的工作，有些代理模式的实现非常复杂。（Spring的依赖注入内部不止要做代理，还要维护工厂生产的组件）