https://github.com/Ecwid/clickhouse-client

Java/Kotlin client for ClickHouse
https://github.com/Ecwid/clickhouse-client

clickhouse clickhouse-client java kotlin

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Java/Kotlin client for ClickHouse

• Host: GitHub
• URL: https://github.com/Ecwid/clickhouse-client
• Owner: Ecwid
• License: apache-2.0
• Created: 2019-01-11T03:24:08.000Z (almost 6 years ago)
• Default Branch: master
• Last Pushed: 2024-08-21T11:16:58.000Z (3 months ago)
• Last Synced: 2024-08-21T13:33:21.618Z (3 months ago)
• Topics: clickhouse, clickhouse-client, java, kotlin
• Language: Kotlin
• Homepage:
• Size: 304 KB
• Stars: 25
• Watchers: 22
• Forks: 9
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
# clickhouse-client

Java/Kotlin client for ClickHouse (https://clickhouse.com)

## How to use

There are three different clients, from raw low-level client to simple object mapper.

### Mapped client (transparently converts response rows into your POJO)

```java

HttpTransport httpTransport = new ApacheHttpClientTransport();

ClickHouseMappedClient client = new ClickHouseMappedClient(httpTransport);

try (MappedResponse response = client.select("http://localhost:8123", "SELECT * FROM user", User::convert)) {

    for (User user : response) {

        System.out.println(user);

    }

}

```

Class `User` and `convert` function can be something like this

```java

class User {

    private final String name;

    private final int age;

    public User(String name, int age) {

        this.name = name;

        this.age = age;

    }

    public static User convert(TypedRow row) {

        String name = row.getString("name");

        int age = row.getInt8("age");

        return new User(name, age);

    }

}

```

### Typed client (looks like JDBC ResultSet class)

```java

HttpTransport httpTransport = new ApacheHttpClientTransport();

ClickHouseTypedClient client = new ClickHouseTypedClient(httpTransport);

try (TypedResponse response = client.select("http://localhost:8123", "SELECT * FROM table")) {

    for (TypedRow typedRow : response) {

        int firstValue = typedRow.getInt32(1);

        Date secondValue = typedRow.getDateTime(2);

        List thirdValue = typedRow.getInt32Array(3);

        System.out.println(firstValue + ":" + secondValue + ":" + thirdValue);

    }

}

```

### Raw client (very low level, use if you want to control everything)

```java

HttpTransport httpTransport = new ApacheHttpClientTransport();

ClickHouseRawClient client = new ClickHouseRawClient(httpTransport);

try (RawResponse response = client.select("http://localhost:8123", "SELECT * FROM table")) {

    for (RawRow row : response) {

        System.out.println(row);

    }

}

```

## How to add clickhouse-client into your project

### Gradle

```

compile "com.ecwid.clickhouse:clickhouse-client:0.15.0"

```

### Maven

```

  com.ecwid.clickhouse

  clickhouse-client

  0.15.0

```

## How to enable metrics in clickhouse-client

### Use prometheus metrics

Add prometheus metric dependency to your project

gradle

```

compile "io.prometheus:prometheus-metrics-core:1.2.0"

```

Inject metrics collector on instantiate client

```java

HttpTransport httpTransport = new ApacheHttpClientTransport();

ClickHouseMappedClient client = new ClickHouseMappedClient(httpTransport, DefaultMetrics.INSTANCE.getPROMETHEUS());

```

### Use custom metrics collector

Add implementation of `com.ecwid.clickhouse.metrics.Metrics` interface

```java

import com.ecwid.clickhouse.metrics.Metrics;

import org.jetbrains.annotations.NotNull;

public class DummyMetrics implements Metrics {

    @Override

    public void measureRequest(@NotNull String host, int statusCode) {

        // Measure request to host with received http status code

    }

    @NotNull

    @Override

    public AutoCloseable startRequestTimer(@NotNull String host) {

        // start measuring request

        final long startedAt = System.currentTimeMillis();

        return new AutoCloseable() {

            @Override

            public void close() throws Exception {

                final long completedAt = System.currentTimeMillis();

                // measure request time to host

            }

        };

    }

}

```

And use it on instantiate client:

```java

HttpTransport httpTransport = new ApacheHttpClientTransport();

ClickHouseMappedClient client = new ClickHouseMappedClient(httpTransport, new DummyMetrics());

```