java 泛型的使用

参考文档

http://www.cnblogs.com/panjun-Donet/archive/2008/09/27/1300609.html

泛型的主要目标是提高 Java 程序的类型安全。通过知道使用泛型定义的变量的类型限制，编译器可以在一个高得多的程度上验证类型假设。

可以查看下 Map, List , Future  等这些java 底层基础代码的写法，一目了然

下面举个我应用中碰到的例子以及写法，之所以举这个例子，主要是因为它包含了多种情况，1 参数是范型，2 返回值是范型，3，参数和返回值都是范型

app 产品中最不能缺的就是 push, 但是 ios 的推送 和 android 的推送还不一样，而且 android 推送还因为不同的第三方平台又不一样，比如小米推送，友盟推送，极光推送，百度云推送，个推推送等等

所以总思路是写一个通用接口，以及一个抽象类（主要是实现发送push）,因为发送push的流程都是一样的，见下面的代码

接口

package com.zyguo.tools.push;

public interface IPush{
    /**
     * 异步发送PUSH
     */
    public boolean sendPushByAsyn( PushBody pushBody );
    
    /**
     * 同步发送PUSH
     * @return 返回错误提示文案，若为 success， 说明发送成功
     */
    public String sendPushBySync( PushBody pushBody, int maxWaitSec );
}

抽象类，因为不同的push通道，发送的消息格式是不一样的，而且返回值的格式也是不一样的（有json, xml ,byte 等等），所以定义了2个范型 M 代表消息，R代表返回值，private String sendPush(PushBody pushBody) {} 就是发送push的通用流程

package com.zyguo.tools.push;

import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import org.apache.log4j.Logger;
import com.zyguo.sdk.thread.BLThreadPool;
import com.zyguo.sdk.utils.BUtils;

public abstract class AbstractPush<M, R extends Object> implements IPush {
    protected Logger log = Logger.getLogger( this.getClass().getName() );
    public final static String SUCCESS = "success";
    private BLThreadPool threadPool = new BLThreadPool();

    
    private String sendPush(PushBody pushBody) {
        try {
            if ( pushBody != null && BUtils.isNotBlank( pushBody.getToken() ) ) {
                long begin = System.currentTimeMillis();
                log.debug("begin send push:" + pushBody );
                M msg = pushBody2message( pushBody );
                R response = sendPush( msg, pushBody.getToken() ); 
                long end = System.currentTimeMillis();
                log.debug("end push，result==" + response + ",耗时：" + ( end - begin ) + "毫秒");
                if ( response != null ) {
                    String result = dealPushResponse( response, pushBody );
                    log.debug("send xiaomi push suceess," + pushBody );
                    return result;
                } else {
                    log.error("no_response," + pushBody);
                    return "no_response";
                }
            } else {
                return "token is null";
            }
        } catch (Exception e) {
            log.error("send xiaomi push exception", e);
            return "exception:" + e.getMessage();
        }
        
    }

    
    protected abstract String dealPushResponse( R response, PushBody pushBody );
    protected abstract M pushBody2message( PushBody pushBody );
    protected abstract R sendPush( M msg, String token );

    @Override
    public boolean sendPushByAsyn( final PushBody pushBody) {
        threadPool.submit( new Runnable() {
            public void run() {
                sendPush( pushBody );
            }
        });
        return true;
    }
    
    @Override
    public String sendPushBySync( final PushBody pushBody, int maxWaitSec ) {
        Future<String> future = threadPool.submit( new Callable<String>() {
            public String call() throws Exception {
                return sendPush( pushBody );
            }
        });
        
        try {
            String result = future.get( maxWaitSec, TimeUnit.SECONDS );
            return result;
        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (ExecutionException e) {
            e.printStackTrace();
        } catch (TimeoutException e) {
            e.printStackTrace();
        } 
        return null;
    }

    public void setThreadPool(BLThreadPool threadPool) {
        this.threadPool = threadPool;
    }


}

小米 push 如下, 具体实现就不写出了

package com.zyguo.tools.push;

import java.io.IOException;
import org.json.simple.parser.ParseException;
import com.xiaomi.push.sdk.ErrorCode;
import com.xiaomi.xmpush.server.Constants;
import com.xiaomi.xmpush.server.Message;
import com.xiaomi.xmpush.server.Message.Builder;
import com.xiaomi.xmpush.server.Result;
import com.xiaomi.xmpush.server.Sender;

public class XiaoMiPush extends AbstractPush<Message, Result>{
    private String appKey;
    private String packageName;
 
    @Override
    protected Message pushBody2message( PushBody pushBody ){
return null;
    }
    
    @Override
    protected String dealPushResponse( Result response, PushBody pushBody ) {
return SUCCESS;
    }

    @Override
    protected Result sendPush(Message msg, String token) {
return null;
    }

    public void setAppKey(String appKey) {
        this.appKey = appKey;
    }

    public void setPackageName(String packageName) {
        this.packageName = packageName;
    }
}

iOS push 如下

package com.zyguo.tools.push;

import com.xiaomi.push.sdk.ErrorCode;
import com.xiaomi.xmpush.server.Constants;
import com.xiaomi.xmpush.server.Message;
import com.xiaomi.xmpush.server.Result;
import com.xiaomi.xmpush.server.Sender;
import com.zyguo.sdk.utils.BUtils;

public class IOSPush extends AbstractPush<Payload, Boolean>{
    @Override
    protected String dealPushResponse(Object response, PushBody pushBody) {
        return null;
    }

    @Override
    protected Payload pushBody2message(PushBody pushBody) {
        return null;
    }

    @Override
    protected boolean sendPush(Payload msg, String token) {
        return null;
    }
}