hdfs调用API

1.启动集群

start-dfs.sh

2.创建项目（重点）

两种下载方式

1，下载sdk1.8不然会有很多错误

2.添加pom.xml的配置文件

<dependencies>
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.12</version>
    </dependency>
    <dependency>
        <groupId>org.apache.logging.log4j</groupId>
        <artifactId>log4j-slf4j-impl</artifactId>
        <version>2.12.0</version>
    </dependency>
    <dependency>
        <groupId>org.apache.hadoop</groupId>
        <artifactId>hadoop-client</artifactId>
        <version>3.1.3</version>
    </dependency>
</dependencies>

3.点击maven，将下面的依赖下载下来

 

4.在项目的src/main /resources目录下，新建一个文件，命名为“log4j2.xml”，在文件中填入

注意这是中文，复制

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="error" strict="true" name="XMLConfig">
    <Appenders>
        <!-- 类型名为Console，名称为必须属性 -->
        <Appender type="Console" name="STDOUT">
            <!-- 布局为PatternLayout的方式，
            输出样式为[INFO] [2018-01-22 17:34:01][org.test.Console]I'm here -->
            <Layout type="PatternLayout"
                    pattern="[%p] [%d{yyyy-MM-dd HH:mm:ss}][%c{10}]%m%n" />
        </Appender>

    </Appenders>

    <Loggers>
        <!-- 可加性为false -->
        <Logger name="test" level="info" additivity="false">
            <AppenderRef ref="STDOUT" />
        </Logger>

        <!-- root loggerConfig设置 -->
        <Root level="info">
            <AppenderRef ref="STDOUT" />
        </Root>
    </Loggers>

</Configuration>

5.创建HdfsClient类

package org.lotus;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.junit.Test;

import java.io.IOException;
import java.net.URI;
import java.net.URISyntaxException;

public class HdfsClient {

/**
 * 客户端代码常用套路
 * 1.获取一个客户端
 * 2.执行相关的操作命令
 * 3.关闭资源
 */
    @Test
    public void testmkdir() throws URISyntaxException, IOException, InterruptedException {
        
        URI uri = new URI("hdfs://172.18.0.2:9000");
        Configuration configuration = new Configuration();
        
        FileSystem fs = FileSystem.get(uri, configuration, "root");

        fs.mkdirs(new Path("/xiyou/huaguoshan"));

        fs.close();
    }
}

 点击运行，查看结果。

问题：

 log4j:WARN No appenders could be found for logger (org.apache.htrace.core.Tracer).
log4j:WARN Please initialize the log4j system properly.
log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>org.lotus</groupId>
  <artifactId>HDFSClient</artifactId>
  <packaging>war</packaging>
  <version>1.0-SNAPSHOT</version>
  <name>HDFSClient Maven Webapp</name>
  <url>http://maven.apache.org</url>

  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.12</version>
    </dependency>
    <dependency>
      <groupId>org.apache.logging.log4j</groupId>
      <artifactId>log4j-slf4j-impl</artifactId>
      <version>2.12.0</version>
    </dependency>
    <dependency>
      <groupId>org.apache.hadoop</groupId>
      <artifactId>hadoop-client</artifactId>
      <version>3.1.3</version>
      <exclusions>
        <!-- 排除 Log4j 1.x -->
        <exclusion>
          <groupId>log4j</groupId>
          <artifactId>log4j</artifactId>
        </exclusion>
        <!-- 排除 SLF4J → Log4j 1.x 的桥接 -->
        <exclusion>
          <groupId>org.slf4j</groupId>
          <artifactId>slf4j-log4j12</artifactId>
        </exclusion>
      </exclusions>
    </dependency>
  </dependencies>

  <build>
    <finalName>HDFSClient</finalName>
  </build>
</project>