解析Mybatis Porxy动态代理和sql解析替换问题

Class.forName("com.Mysql.jdbc.Driver");
Connection connection = DriverManager.getConnection("");

static {
    loadInitialDrivers();
    println("JDBC DriverManager initialized");
}

private static void loadInitialDrivers() {
    String drivers;
    // 访问修饰符，在这里把 jdbc.drivers 拿出来
    try {
        drivers = AccessController.doPrivileged(new PrivilegedAction<String>() {
            public String run() {
                return System.getProperty("jdbc.drivers");
            }
        });
    } catch (Exception ex) {
        drivers = null;
    }

    AccessController.doPrivileged(new PrivilegedAction<Void>() {
        public Void run() {
            // 读取拿出 driver 和 所有迭代器
            ServiceLoader<Driver> loadedDrivers = ServiceLoader.load(Driver.class);
            Iterator<Driver> driversIterator = loadedDrivers.iterator();
            
            // 一直进行迭代
            try{
                while(driversIterator.hasNext()) {
                    driversIterator.next();
                }
            } catch(Throwable t) {
            // Do nothing
            }
            return null;
        }
    });

    println("DriverManager.initialize: jdbc.drivers = " + drivers);

    if (drivers == null || drivers.equals("")) {
        return;
    }
    String[] driversList = drivers.split(":");
    println("number of Drivers:" + driversList.length);
    for (String aDriver : driversList) {
        try {
            println("DriverManager.Initialize: loading " + aDriver);
            Class.forName(aDriver, true,
                    ClassLoader.getSystemClassLoader());
        } catch (Exception ex) {
            println("DriverManager.Initialize: load failed: " + ex);
        }
    }
}

Statement statement = connection.createStatement();
ResultSet resultSet = statement.executeQuery("select * from mybatis.user");
    while (resultSet.next()) {
      int id = resultSet.getInt(1);
      String username = resultSet.getString(2);
      list.add(new User(id,username));
}

interface UserMapper {
  @Select("select * from mybatis.user where id =#{id}")
  List<User> selectUserList();
}

public static void main(String[] args) {
  UserMapper userMapper = (UserMapper) Proxy.newProxyInstance(
    JDKMybatis.class.getClassLoader(),
    new Class<?>[]{UserMapper.class},
    new InvocationHandler() {
      
      @Override
      public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        // 把注解类获取，可以查出注解的值等多种其他值
        Select annotation = method.getAnnotation(Select.class);
        if (annotation != null) {
          String[] value = annotation.value();
          System.out.println(Arrays.toString(value));
        }
        return null;
      }
    });

  userMapper.selectUserList(1);
}

public static Object newProxyInstance(ClassLoader loader,
                                      Class<?>[] interfaces,
                                      InvocationHandler h)

<plugins>
    <plugin>
        <groupId>org.apache.Maven.plugins</groupId>
        <artifactId>maven-compiler-plugin</artifactId>
        <configuration>
            <compilerArgument>-parameters</compilerArgument>
            <source>1.8</source>
            <target>1.8</target>
        </configuration>
    </plugin>
</plugins>

private static String parseSql(String sql, Map<String, Object> argsNameMap) {
  // 定义为常量数组
  char[] str = {'#', '{'};
  StringBuilder stringBuilder = new StringBuilder();
  for (int i = 0; i < sql.length(); i++) {
    char aloneParseSql = sql.charAt(i);

    if (str[0] == aloneParseSql) {
      int nextIndex = i + 1;
      char nextChar = sql.charAt(nextIndex);

      // # 后应该是 { ，不匹配直接抛出异常
      if (str[1] != nextChar) {
        throw new RuntimeException(String.fORMat(
          "此处应该是：#{\n sql：%s\n index：%d",
          stringBuilder.toString(), nextIndex));
      }
      
      StringBuilder partStringBuilder = new StringBuilder();
      i = partParseSql(partStringBuilder, sql, nextIndex);
      String argsName = partStringBuilder.toString();
      Object argsValue = argsNameMap.get(argsName);
      stringBuilder.append(argsValue.toString());
    }

    // 如果没有条件，直接追加
    stringBuilder.append(aloneParseSql);
  }
  return stringBuilder.toString();
}

private static int partParseSql(StringBuilder partStringBuilder, String sql, int nextIndex) {
  // 由于 nextIndex 当前指针指向的是 { 所以要加一位，把后面内容解析
  nextIndex++;
  char[] str = {'}'};
  for (; nextIndex < sql.length(); nextIndex++) {
    char indexSql = sql.charAt(nextIndex);
    if (str[0] != indexSql) {
      partStringBuilder.append(indexSql);
    }
    if (str[0] == indexSql) {
      return nextIndex;
    }
  }
  throw new RuntimeException(String.format(
    "缺少：}\n index：%d",
    nextIndex));
}

@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
  // 把注解类获取，可以查出注解的值等多种其他值
  Select annotation = method.getAnnotation(Select.class);
  Map<String, Object> argsNameMap = MapBuildArgsName(method, args);
  if (annotation != null) {
    String[] value = annotation.value();
    String sql = value[0];
    sql = parseSql(sql, argsNameMap);
    System.out.println(sql);
  }
  return null;
}