README

项目功能

​ 为达到Service 从公网访问客户端所在内网中数据源的效果，通过运行在客户机上的代理程序代理Service的所有JDBC请求，并将查询结果返回给Service。实现目标，Service除更改使用的JDBC驱动外，对代理存在无感知，支持主流的包含JDBC支持的数据库。

项目依赖

Netty-socketio与Socket.io-client-Java的对应关系是：

netty-socketio	Java client
1.7.19	1.0.x
暂无	Document

以下用Service指代Socket连接中的socket服务器，它也是需求查询用户内网数据源的公网服务器。

用Agent指代Socket连接中的客户端，也是运行在用户PC上承担远程调用JDBC方法的代理服务。

具体结构见下文项目结构图。

Quick Start

1. 运行Service模块下 ServiceTest
2. 运行Agent下 Test

实现方案

1. Service 启动socket服务与 Agent建立连接后，可以开始使用代理进行查询。

2. Service端通过自实现的JDBC驱动，进行JDBC操作。驱动中使用基于CGlib的动态代理，对Service端的所有JDBC相关驱动类进行增强，所有方法信息会被序列化传递到Agent执行，并有选择地将结果回送到Service

结构与流程

如上图，对于Service 端来讲，Agent对其的代理是无感知的。在Service来看，只是调用了一个自定义的JDBC驱动进行查询。

这得益于驱动内部方法地重写，自定义地实现类在Agent和Service中有相同的名字，但内部实现却不相同，这使得整个RPC的流程十分灵活。

方案细节

动态代理

动态代理是该项目中的核心，如在 Driver类的 connect方法中：返回的Connection就被替换为了动态代理增强过的MyConnection，实现对Service中调用的JDBC方法的完全代理。代理类会依靠info从缓存中找到命名空间（本项目中以/dataSoure Name来区别命名空间）对应的socket,将方法调用信息以RPCReqquest的方式序列化后发送出去。

 	// In Service Source Code
	@Override
    public Connection connect(String url, Properties info) throws SQLException {
        String agentID = info.getProperty("agentID");
        String dbName = info.getProperty("agentDBName");
        if(dbName == null){
            dbName = url.split(":")[1];
            info.setProperty("agentDBName", dbName);
        }
        MyConnection myConn = (MyConnection) ProxyFactory.getProxy(MyConnection.class, info);
        myConn.setInfo(info);
        return myConn;
    }

RPC实体类包含如下信息：

@Data
@Accessors(chain = true)
public class RpcRequest {
    // Marks whether the method delivered need loopback data
    private boolean reply;
    // Marks whether the method will create an instance requeired to be cached.
    private boolean binding;
    private String ID;
    private String IDtoInvoke;
    private Class ServiceClass;
    private String MethodName;
    private Object[] args;
    private Class[] argTypes;
}

在Agent收到Request的时候，会按照报文要求对方法进行调用，某些创建的实例会被缓存，以便之后调用。在本项目中，这些实例的类是：

Drive( MyDriver ), Connection( MyConnection ), Statement( MyStatement ), PreparedStatement( MyPreparedStatement ), ResultSet( MyResult )

public Object invokeAsRequest(RpcRequest rpcRequest, BeanCache beanCache) {
...
        // The ID of the rpcRequest could be save as the ID of an instance
        // Because one instance can only been create just once for an unique rpcRequest
        String IDtoCache = rpcRequest.getID();
        String IDtoInvoke = rpcRequest.getIDtoInvoke();
...

注解解耦

在Service端，定义了以下注解。

annotation
 - BindingParameter
 - LocalMethod
 - RemoteClass
 - WithBindingParameter

如上文所说，注册了自定义驱动后。生成的增强类所调用的方法都会生成 RPC 请求，为了能够松散的实现对不同方法的请求控制，需要一些自定义的注解。

LocalMethod：方法注释，标记不需要远程调用的方法。

RemoteClass：类注释，标记该类远程调用时对应的类。

WithBindingParameter: 方法注释，标记包含绑定类方法。因为绑定类作为参数时，实际需要传递的实际是Agentxx类中持有的成员变量。

BindingParameter: 参数注释，标记参数中的绑定类。

在Agent端，定义了以下注解注解。

annotation
 - BindClass
 - BindingParameter
 - WithBindingParameter

BindingPatameter和WithBindingParameter同上。

BindClass：类注释，标记绑定类，在Agent中用于判断该实例是否需要缓存。

RPC调用

在一次RPC调用流程中，FutureTask 异步获取返回结果，以“生产者-消费者”模型实现一次调用的同步管理。

ClientWrapper 持有着各个命名空间上的socket。在这些socket上的通信，每次调用，会在wrapper中注册一个工具类:LockAndCondition，发出消息后，等待socket上出现对应的响应报文唤醒FutureTask 线程。通过锁机制，保证逻辑的正确性。

@Data
@AllArgsConstructor
@NoArgsConstructor
public class ClientWrapper {
        private SocketIOClient client;
        private static Map<String, LockAndCondition> lockMap = new ConcurrentHashMap<>();


        public SocketIOClient getClient(){
                if(client == null) throw new RuntimeException("no such client");
                return client;
        }

        public LockAndCondition getLockAndCondition(String messageID){
                LockAndCondition lac = lockMap.get(messageID);
                if(lac == null){
                        ReentrantLock lock = new ReentrantLock();
                        Condition condition = lock.newCondition();
                        lac = new LockAndCondition(lock, condition);
                        lockMap.put(messageID, lac);
                }
                return lac;
        }
    
        public void removeLockAndCondition(String messageID){
                lockMap.remove(messageID);
        }
}

@Data
@NoArgsConstructor
@AllArgsConstructor
public class LockAndCondition{
    private ReentrantLock lock;
    private Condition condition;
    private Object result;
    private String BindingID;

    LockAndCondition(ReentrantLock lock, Condition condition){
        this.lock = lock;
        this.condition = condition;
    }
}

 FutureTask<Object> futureTask = new FutureTask<Object>(
                new Callable<Object>() {
                    @Override
                    public Object call() throws Exception {
                        Object res = null;
                        ClientWrapper wrapper = ClientCache.getClientWrapper(agentID, dbName);
                        LockAndCondition lac = wrapper.getLockAndCondition(rpcRequest.getID());
                        ReentrantLock lock = lac.getLock();
                        Condition condition = lac.getCondition();
                        try{
                            byte[] bytes = ServerStater.serializer.serialize(rpcRequest);
                            lock.lock();
                            client.sendEvent("RPCRequest", bytes);
                            condition.await();
                            // get res from RPC response data
                            res = lac.getResult();
                        }catch (Exception e){
                            e.printStackTrace();
                        }finally {
                            lock.unlock();
                        }
                        return res;
                    }
                }
        );
        ServerStater.threadPool.submit(futureTask);
        Object res = futureTask.get();

socket收到响应时解锁对应的线程。

		// rpcResponse
		   nameSpace.addEventListener("RPCResponse", byte[].class, ((client, data, ackRequest) -> {
            RpcResponse rpcResponse = serializer.deserialize(data, RpcResponse.class);
            logger.debug("RPCResponse: " + (rpcResponse.getStatus() ? "success" : "fail"));

            String agentID = Commons.getAgentID(client);
            String dbName = Commons.getDBName(client);
            ClientWrapper wrapper = ClientCache.getClientWrapper(agentID, dbName);
            LockAndCondition lac = wrapper.getLockAndCondition(rpcResponse.getID());
            ReentrantLock lock = lac.getLock();
            Condition condition = lac.getCondition();
            // When a response is received, it notifies that the futuretask thread blocking on the lockandcondition 
            // If the response contains data, take it out. 
            try {
                lock.lock();
                Object resultData = rpcResponse.getResult();
                if(!rpcResponse.getStatus()){
                    logger.error(resultData);
                    resultData = null;
                }
                if(resultData != null) lac.setResult(resultData);
                condition.signal();
            }catch (Exception e){
                e.printStackTrace();
            }finally {
                lock.unlock();
            }
            wrapper.removeLockAndCondition(rpcResponse.getID());
            logger.debug("received response message, signaled condition");
        }));

Service是使用netty实现的高效同步非阻塞IO，上文的同步机制可以很大程度上利用socket的并发效果。

绑定实例

确定Agent上缓存实例与Service端实例的一一对应关系是很必要，不然程序在反射调用方法时会产生问题。

例如，对于createStatement()方法必须由上一步生成的Connection类进行调用。为了达到这一点，这些Service端实例必须和Agent端具有相同的ID。

考虑到在进行RPC调用回调的时候，利用时间和随机数生成了一个唯一ID。

	public static String getID(){
        return getTimeInMillis() + getRandom();
    }

    public static String getTimeInMillis() {
        long timeInMillis = Calendar.getInstance().getTimeInMillis();
        return timeInMillis+"";
    }

    public static String getRandom() {
        Random random = new Random();
        int nextInt = random.nextInt(9000000);
        nextInt=nextInt+1000000;
        String str=nextInt+"";
        return str;
    }

而Agent端的缓存实例是由某次调用产生的，所以只需将该次调用的RPC报文ID标记在实例上，并在收到RPC响应时为需要绑定的类型打上同样的标记即可。这样Agent方面，由于存储的实例都有了唯一的ID作为键，大大简化了缓存系统的复杂性。

标记实现：

@Override
public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable {		...
		
     Object returnObj = methodProxy.invokeSuper(o, objects);

     // If the return instance is corresponding with another instance in agent, set the binding ID.
     if (InterceptorUtils.isInBindList(returnObj)){
     	InterceptorUtils.setInvokeHelper(returnObj, "setID", rpcRequest.getID());
     }

测试

测试在Intranet中test内。

启动流程

1. 构造客户端与服务端实例

   可见于AbstractDriverTest类

   static final String[][] dbNameAndDriver = new String[][]{
               DBProperties.HSQL
       };
   
   	// 服务端与客户端应注册同样的一个或多个驱动，但服务端中不需要加载，仅仅用于构造命名空间
       static final ServerStater server = new ServerStater(dbNameAndDriver);
       static final AgentStarter agent =  new AgentStarter(dbNameAndDriver);
   

2. 此时 代理端/服务端 实例已经启动，服务端应优先注册代理端信息，否则会报错。

   info.setProperty("user", "sa");
   info.setProperty("password", "");
   info.setProperty("agentID", "1001");
   info.setProperty("agentDBName", DBProperties.HSQL[0]);
   

3. 模拟服务端等待连接

   static void openSocket(){
           while(ClientCache.getClient(
                   info.getProperty("agentID"),
                   info.getProperty("agentDBName"))
                   == null){
           }
       }
   

4. 连接就绪即可获取连接，此时运行TestSuit即可。

使用Junit5 和 HSQL 进行集成测试

这一次项目的测试记录，项目用 IDEA 编写，Junit 5进行单元测试，HSQL DB提供方便的内存数据库。

Use Junit 5

Configuring JUnit Platform

To get started with JUnit Platform, you need to add at least a single TestEngine implementation to your project. For example, if you want to write tests with Jupiter, add the test artifact junit-jupiter-engine to the dependencies in POM:

<dependencies>    
    [...]    
    <dependency>        
    	<groupId>org.junit.jupiter</groupId>        
        <artifactId>junit-jupiter-engine</artifactId>        
        <version>5.4.0</version>        
        <scope>test</scope>    
    </dependency>    
    [...]
</dependencies>

This will pull in all required dependencies. Among those dependencies is junit-jupiter-api which contains the classes and interfaces your test source requires to compile. junit-platform-engine is also resolved and added.

This is the only step that is required to get started - you can now create tests in your test source directory (src/test/java).

集成测试的细节

生命周期

In order to allow individual test methods to be executed in isolation and to avoid unexpected side effects due to mutable test instance state, JUnit creates a new instance of each test class before executing each test method (see Test Classes and Methods). This "per-method" test instance lifecycle is the default behavior in JUnit Jupiter and is analogous to all previous versions of JUnit.

If you would prefer that JUnit Jupiter execute all test methods on the same test instance, annotate your test class with @TestInstance(Lifecycle.PER_CLASS). When using this mode, a new test instance will be created once per test class. Thus, if your test methods rely on state stored in instance variables, you may need to reset that state in @BeforeEach or @AfterEach methods.

根据官方文档，Junit5的默认测试实例的生命周期为pre-method在集成测试时，应当选择pre_class，即一个测试类创建一个实例。

成员变量

在pre-class的生命周期下，整个测试过程中，测试方法有时需要共享变量。比如进行JDBC查询的时候，只需要共用一个connection，甚至是一个statement.

Method Order

Although true unit tests typically should not rely on the order in which they are executed, there are times when it is necessary to enforce a specific test method execution order — for example, when writing integration tests or functional tests where the sequence of the tests is important, especially in conjunction with @TestInstance(Lifecycle.PER_CLASS)

除上述两点之外，在集成测试中，必不可少的一项是使用Order控制方法的执行顺序。

例子：

import org.junit.jupiter.api.MethodOrderer.OrderAnnotation;
import org.junit.jupiter.api.Order;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.TestMethodOrder;

@TestMethodOrder(OrderAnnotation.class)
class OrderedTestsDemo {

    @Test
    @Order(1)
    void nullValues() {
        // perform assertions against null values
    }

    @Test
    @Order(2)
    void emptyValues() {
        // perform assertions against empty values
    }

    @Test
    @Order(3)
    void validValues() {
        // perform assertions against valid values
    }

}

使用 HSQL DB

运行模式

HSQL DB 是一款纯Java编写的免费数据库，并且支持Memory-Only模型，所以每个单测使用独立的数据库就有了可能，Memory-Only模型数据不会持久化跑完即销毁，从根源上解决了测试难以复现和测试对数据的污染问题。

Memory-Only 内存模式

版本问题

maven 依赖

		<dependency>
            <groupId>org.hsqldb</groupId>
            <artifactId>hsqldb</artifactId>
            <version>2.5.2</version>
            <scope>test</scope>
        </dependency>

根据官网:

Latest version 2.7.0 works with JDK 8 and above. Version for JDK 6 is also available.

但是这不代表在测试的时候可以直接调用 2.7.0 版本的代码，因为该版本使用 jdk 11 编译，在使用 IDEA 测试时，直接引用会报错，所以版本应该选择 2.5x .

代码：

public class TestHSQL{

    @BeforeAll
    static void startHSQL(){
        try {
            Class.forName(DBProperties.HSQL_DTIVER_NAME);
            Thread.sleep(1000);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    ...
        
}

错误信息：

java.lang.UnsupportedClassVersionError: org/hsqldb/jdbcDriver has been compiled by a more recent version of the Java Runtime (class file version 55.0), this version of the Java Runtime only recognizes class file versions up to 52.0

语法问题

HSQL 与 MySQL 语法并不相同，HSQL语法，英文文档读起来稍微有点费劲。

CREATE TABLE student1 (
                    student_id int(32) PRIMARY KEY AUTO_INCREMENT NOT NULL, 
                    student_name varchar(100) NOT NULL,
                    student_address varchar(100) NOT NULL 
                    );

如上的sql语句在程序中要这么写，差别还是很多的，对于大部分在标准 SQL 语句之外的语句都需要先检查是否使用了正确的语法。

st.executeUpdate("CREATE TABLE student (" +
                    "student_id INTEGER GENERATED BY DEFAULT AS IDENTITY " +
                    "(START WITH 1, INCREMENT BY 1) NOT NULL," +
                    "student_name VARCHAR(100) NOT NULL," +
                    "student_address VARCHAR(100) NOT NULL," +
                    "PRIMARY KEY (student_id)" +
                    ");");

其实还有个取巧的方法，可以使用参数直接开启mysql语法支持，但依然有些语法MySQL特点HSQKDB并不支持，此时应参考HDBSQL所实现的SQL92标准。

"jdbc:hsqldb:mem:test;sql.syntax_mys=true"

使用示例

	
import com.fanruan.AgentStarter;
import com.fanruan.ServerStater;

import com.fanruan.service.jdbc.driver.ServiceDriver;
import com.fanruan.proxy.ProxyFactory;
import com.fanruan.utils.DBProperties;
import org.junit.jupiter.api.*;

import java.sql.*;
import java.util.Properties;

/**
 * @author Yichen Dai
 * @date 2022/8/18 15:27
 */

@TestInstance(TestInstance.Lifecycle.PER_CLASS)
@TestMethodOrder(MethodOrderer.OrderAnnotation.class)
public class TestUtil {

    static Connection conn = null;
    static Statement st = null;
    static PreparedStatement pst = null;
    static ResultSet rs = null;

    static void configService(){
        // 启动socket服务器
        String[][] DBs = new String[][]{
                DBProperties.HSQL,
        };
        new ServerStater(DBs);
    }

    static void configAgent(){
        // 启动socket客户端
        String[][] DBs = new String[][]{
                DBProperties.HSQL,
        };
        new AgentStarter(DBs);
    }

    @BeforeAll
    static void autoConfig(){
        configService();
        configAgent();
        try {
            // 等待socket连接
            Thread.sleep(2000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    @Test
    @Order(1)
    void testConnect() throws SQLException {
        // 建立连接
        Properties info = new Properties();
        info.setProperty("user", "sa");
        info.setProperty("password", "");
        info.setProperty("agentID", "1001");
        info.setProperty("agentDBName", DBProperties.HSQL[0]);

        Driver driver = (ServiceDriver) ProxyFactory.getProxy(ServiceDriver.class, null);
        conn = driver.connect("jdbc:hsqldb:mem:test;sql.syntax_mys=true", info);
    }

    @Test
    @Order(2)
    void testCreateTable1() throws SQLException {
        // 创建 statement
        st = conn.createStatement();

        // 创建表
        int num = st.executeUpdate("DROP TABLE student IF EXISTS;");

        Assertions.assertEquals(0, num);


        num = st.executeUpdate("CREATE TABLE student (" +
                "student_id INTEGER GENERATED BY DEFAULT AS IDENTITY " +
                "(START WITH 1, INCREMENT BY 1) NOT NULL," +
                "student_name VARCHAR(100) NOT NULL," +
                "student_address VARCHAR(100) NOT NULL," +
                "PRIMARY KEY (student_id)" +
                ");");

        Assertions.assertEquals(0, num);
    }

    @Test
    @Order(3)
    void testCreateTable2() throws SQLException {
        // 创建表
        int num = st.executeUpdate("DROP TABLE student_score IF EXISTS;");

        Assertions.assertEquals(0, num);


        num = st.executeUpdate("CREATE TABLE score (" +
                "student_id int(10) PRIMARY KEY NOT NULL," +
                "score int(10) NOT NULL" +
                ");"
        );

        Assertions.assertEquals(0, num);
    }

    @Test
    @Order(4)
    void testInsert1() throws SQLException {
        // 插入数据
        int num = st.executeUpdate("INSERT INTO student VALUES" +
                "(1, '张三', '上海')," +
                "(2, '李四', '北京')," +
                "(3, '王五', '成都');");

        Assertions.assertEquals(3, num);
    }

    @Test
    @Order(5)
    void testInsert2() throws SQLException {
        // 插入数据
        int num = st.executeUpdate("INSERT INTO score VALUES" +
                "(1, 645)," +
                "(2, 627)," +
                "(3, 591);");

        Assertions.assertEquals(3, num);
    }

    @Test
    @Order(6)
    void testUpdate() throws SQLException {
        // 预查询语句 删除指定 ID
        pst = conn.prepareStatement("UPDATE student" +
                " SET student_name = '李华', student_address = '杭州'"+
                "WHERE student_id = ?");

        Assertions.assertNotNull(pst);

        pst.setInt(1, 1);

        int num = pst.executeUpdate();

        Assertions.assertEquals(1, num);
    }

    @Test
    @Order(7)
    void testDelete() throws SQLException {
        // 预查询语句 删除指定 ID
        pst = conn.prepareStatement("delete from student where student_id = ?");

        Assertions.assertNotNull(pst);

        pst.setInt(1, 3);

        int num = pst.executeUpdate();

        Assertions.assertEquals(1, num);
    }

    @Test
    @Order(8)
    void testSelect() throws SQLException {
        rs = st.executeQuery("select * from student;");

        String[] nameStrings = new String[]{"李华", "李四", "王五"};
        String[] addressString = new String[]{"杭州", "北京", "成都"};

        // 结果集断言
        int num = 1;
        while(rs.next()) {
            Assertions.assertEquals(num, rs.getInt("student_id"));
            Assertions.assertEquals(nameStrings[num-1], rs.getString("student_name"));
            Assertions.assertEquals(addressString[num-1], rs.getString("student_address"));
            num++;
        }
    }

    @Test
    @Order(9)
    void testSubSelect() throws SQLException {
        // 插入数据
        rs = st.executeQuery(
                "SELECT student_name FROM student " +
                "WHERE student_id IN " +
                "(SELECT student_id " +
                "FROM score " +
                "WHERE score > 600);"
        );

        String[] nameStrings = new String[]{"李华", "李四", "王五"};


        // 结果集断言
        int num = 1;
        while(rs.next()) {
            Assertions.assertEquals(nameStrings[num-1], rs.getString("student_name"));
            num++;
        }
    }

    @Test
    @Order(10)
    void testJoin() throws SQLException {
        // 插入数据
        rs = st.executeQuery(
                "SELECT A.student_name " +
                        "FROM student A JOIN score B " +
                        "ON A.student_id = B.student_id " +
                        "WHERE score > 600;"
        );

        String[] nameStrings = new String[]{"李华", "李四", "王五"};

        // 结果集断言
        int num = 1;
        while (rs.next()) {
            Assertions.assertEquals(rs.getString("student_name"), nameStrings[num - 1]);
            num++;
        }
    }
}

开发手册

Service 添加JDBC类

实现接口

1. 以`Service` + `接口名`命名一个类
2. 实现接口
3. 继承`BasedBind`类
4. 对于返回类属于绑定类的情况
 1. 使用代理工厂返回替身类
 2. 如果该类也有会返回绑定类的方法，对该类调用`setInfo(info)`
5. 为该类添加`RemoteClass(remoteClassName = Agent上对应类的全限定类名)`注解。

继承抽象类

1. 以Service + 抽象类名命名一个类

2. 继承抽象类

3. 粘贴所需方法和字段

    private String ID;
   
       @LocalMethod
       public String getID(){
           return this.ID;
       }
   
       @LocalMethod
       public void setID(String ID){
           this.ID = ID;
       }
   
       @LocalMethod
       @Override
       public int hashCode(){
           return super.hashCode();
       }
   
       @LocalMethod
       @Override
       public boolean equals(Object obj) {
           return super.equals(obj);
       }
   
       @LocalMethod
       @Override
       protected Object clone() throws CloneNotSupportedException {
           return super.clone();
       }
   
       @LocalMethod
       @Override
       public String toString() {
           return super.toString();
       }
   
       @LocalMethod
       @Override
       protected void finalize() throws Throwable {
           super.finalize();
       }
   

   4. 对于返回类属于绑定类的情况（包括抽象方法）

      1. 使用代理工厂返回替身类
      2. 如果该类也有会返回绑定类的方法，对该类调用setInfo(info)

   5. 为该类添加RemoteClass(remoteClassName = Agent上对应类的全限定类名)注解。

Agent 添加 JDBC类

实现接口

1. 以`Agent + 接口名`命名一个类
2. 实现接口
3. 组合一个接口类型的成员变量，创建一个入参为该接口类型的构造方法
4. 重写该接口的所有方法
 1. 返回值为普通变量，直接用3中成员变量调用该方法
 2. 返回值为绑定对象，返回包装对象：`new Agent+接口名(成员变量.方法(参数))`
 3. 链式调用方法return this
5. 为该类添加`BindClass`注解

继承抽象类

1. 以`Agent + 继承类名`命名一个类
2. 继承类
3. 组合一个接口类型的成员变量，创建一个入参为该接口类型的构造方法
4. 重写该接口的所有方法(包括继承的抽象方法)
 1. 返回值为普通变量，直接用3中成员变量调用该方法
 2. 返回值为绑定对象，返回包装对象：`new Agent+接口名(成员变量.方法(参数))`
 3. 链式调用方法return this
5. 为该类添加`BindClass`注解

项目参考

nuzzle: A Simple RPC Project

CSV JDBC Driver