Java代码在两个或多个具有相同代码的方法中重用

Question

我在Java中使用以下代码来查询数据库：

public interface MapReduceDAO {

    String host = "mysql";
    int port = 3306;
    String user = "root";
    String password = "root";
    String dbName = "customers";

    default String customersMysqlUrl(String name) {
        return getDocker().containers().container(name).port(port).inFormat("$HOST:$EXTERNAL_PORT");
    }

    default void checkTableHasData(Duration atMost, String tableName) throws Exception {
        try (MysqlQuery mysqlQuery = new MysqlQuery(customersMysqlUrl(host), dbName, user, password)) {

            await().atMost(atMost).pollDelay(Duration.ONE_SECOND).ignoreExceptions().until(
            () -> mysqlQuery.count("SELECT COUNT(*) FROM " + tableName),
            is(Matchers.greaterThan(0)));
        }
    }

    default void checkExistsQuery(Duration atMost, String tableName, int countValueExpected) throws Exception {
    try (MysqlQuery mysqlQuery = new MysqlQuery(customersMysqlUrl(host), dbName, user, password)) {

        await().atMost(atMost).pollDelay(Duration.ONE_SECOND).ignoreExceptions().until(
        () -> mysqlQuery.count("SELECT COUNT(*) FROM " + tableName),
        is(Matchers.equalTo(countValueExpected)));
    }
}

    DockerComposeRule getDocker();
}

如何避免使用重复代码。 在方法checkTableHasData和checkExistsQuery中，我大多重复代码。

编辑：忘记提及，他们最后可能会有不同的断言，例如：

是（Matchers.greaterThan（0）））;

是（Matchers.equalTo（countValueExpected）））;

Answer 1

如果我看到它正确，那些方法只有你给count()的参数不同。 只需介绍一个方法，将其作为参数并使用不同的值调用它。

default void checkTableHasData(Duration atMost, String tableName) throws Exception {
    check(atMost, "SELECT COUNT(*) FROM " + tableName);
}

default void checkTableRowExistSearchOnColumn(Duration atMost, String tableName, String columnName,
                                              String columnValue) throws Exception {
    check(atMost, "SELECT COUNT(*) FROM " + tableName + " where " + columnName +
                               " = " + columnValue);
}

private void check(Duration atMost, String countStatement) throws Exception {
    try (MysqlQuery mysqlQuery = new MysqlQuery(customersMysqlUrl(host), dbName, user, password)) {

        await().atMost(atMost).pollDelay(Duration.ONE_SECOND).ignoreExceptions().until(
        () -> mysqlQuery.count(countStatement),
        is(Matchers.greaterThan(0)));
    }
}

Answer 2

您可以在单独的方法中简单地提取常见行为：

default void checkTableHasData(Duration atMost, String tableName) throws Exception {
    checkExistsQuery("SELECT COUNT(*) FROM " + tableName),
}

default void checkTableRowExistSearchOnColumn(Duration atMost, String tableName, String columnName,
                                              String columnValue) throws Exception {
    checkExistsQuery("SELECT COUNT(*) FROM " + tableName + " where " + columnName +
                               " = " + columnValue),
}

private static void checkExistsQuery(Duration atMost, String query) {
    try (MysqlQuery mysqlQuery = new MysqlQuery(customersMysqlUrl(host), dbName, user, password)) {

        await().atMost(atMost).pollDelay(Duration.ONE_SECOND).ignoreExceptions().until(
        () -> mysqlQuery.count(query),
        is(Matchers.greaterThan(0)));
    }
}