我想开始使用Avro和Map Reduce。有人可以建议一个很好的教程/示例来开始。我无法通过互联网搜索找到很多。
答案 0 :(得分：17)
我最近做了一个严重基于Avro数据的项目，之前没有使用过这种数据格式，我不得不从头开始。你是对的，因为在开始使用Avro时很难获得在线资源的帮助。我建议你的材料是：
最后，我的最后一个建议是使用 Avro 1.4.1与Hadoop 0.20.2 ，并且仅使用该组合。我在使用Hadoop 0.21和更新的Avro版本运行代码时遇到了一些重大问题。
答案 1 :(得分：2)
其他链接：
我在文档中看到的主要问题（确实存在的问题很少）是它专注于非常费力的“通用”方法;这看起来很奇怪，因为它结合了两者的最坏情况 - 您仍然必须提供完整的数据模式，但不会从静态类型等中获益。 自动代码生成更方便，但覆盖率不高。
答案 2 :(得分：2)
https://github.com/apache/avro/blob/trunk/lang/java/mapred avro源代码确实有例子。例如TestReflectJob帮助我使用预定义的域对象编写map-reduce作业
答案 3 :(得分：0)
javascript + jquery：https://codepen.io/GentjanLikaj/pen/dyPXLXX
$( "#btn1" ).click(function() {
$( "table" ).remove();
var text1 = document.getElementById('text').value;
var text1=text1.replace(/(\r\n|\n|\r)/gm,"");
var sep = document.getElementById('sep').value;
var aray = text1.split(sep);
var formato = '<select class="form"><option value="string">string</option><option value="int">int</option><option value="date">date</option><option value="datetime">datetime</option><option value="float">float</option><option value="varchar(50)">varchar</option></select>';
var univoco = '<input id="checkbox" type="checkbox" name="univoco" value="true" > <br>';
var null1 = '<input id="null" class="null11" type="checkbox" name="univoco" value="null" checked> <br>';
var html = '<table id="tbl" class="table table-sm table-striped table-centered .thead-dark "><thead class="thead-dark"><tr class="table-primary"><th scope="col">ColummnName</th><th scope="col">Format</th> <th scope="col">Null</th> </tr> </thead> <tbody>';
$.each(aray, function(i, val) {
html += '<tr><td id = "val">' + val + '</td><td id = "form">' + formato + '</td><td id = "nul">' + null1 + '</td></tr>';
});
html += '</tbody></table>';
$("#table").append(html);
});
$( "#btn2").click(function() {
$( "#avro" ).empty();
var myRows = {myRows:[]};
var $th = $('#tbl th');
$('#tbl tbody tr').each(function(i, tr){
var obj = {},
$tds = $(tr).find('td');
$td1 = $(tr).find('select.form').children("option:selected");
$tds2 = $(tr).find('#checkbox');
$tds3 = $(tr).find('#null');
$th.each(function(){
obj['name'] = $tds.eq(0).text();
var type=$td1.eq(0).val();
var nullv=$tds3.eq(0).is(':checked');
if (type=='date') {
type={type:"int", logicalType:"date"};
}else if (nullv == true) {
type = [type ,'null' ];
}
else{
type;
}
obj['type'] = type;
// obj['univoco'] = $tds2.eq(0).is(':checked');
// obj['null'] = $tds3.eq(0).is(':checked');
});
myRows.myRows.push(obj);
});
console.log(JSON.stringify(myRows));
var header = '{ <br>     "type": "record" , <br>     "namespace": "Mezzora" , <br>     "name": "ReportDSL" , <br>     "fields": [ <br>';
$('#avro').append(header);
text ='          '+JSON.stringify(myRows.myRows[0]) +"<br>";
$('#avro').append(text);
var i;
for (i = 1; i < myRows.myRows.length; i++) {
text ='          ,'+ JSON.stringify(myRows.myRows[i]) +"<br>";
$('#avro').append(text);
}
var footer = '        ] <br> }';
$('#avro').append(footer);
});
$( "#btn3").click(function() {
$( "#sql" ).empty();
var myRows = {myRows:[]};
var $th = $('#tbl th');
$('#tbl tbody tr').each(function(i, tr){
var obj = {},
$tds = $(tr).find('td');
$td1 = $(tr).find('select.form').children("option:selected");
$tds2 = $(tr).find('#checkbox');
$tds3 = $(tr).find('#null');
$th.each(function(){
obj['name'] = $tds.eq(0).text();
var type=$td1.eq(0).val();
var nullv=$tds3.eq(0).is(':checked');
if (nullv == false) {
type= type +' not null';
}else if (nullv == true) {
type = type +' null' ;
}else{
if (type == 'string') {
type = 'varchar(50)';
}else{
type;
}
}
obj['type'] = type;
// obj['univoco'] = $tds2.eq(0).is(':checked');
// obj['null'] = $tds3.eq(0).is(':checked');
});
myRows.myRows.push(obj);
});
console.log(JSON.stringify(myRows));
var header = 'CREATE TABLE [schema].[tblName]   ( <br>';
$('#sql').append(header);
var i;
for (i = 0; i < myRows.myRows.length; i++) {
text ='          '+ JSON.stringify(myRows.myRows[i].name).replace('\"',' ').replace('\"',' ') +JSON.stringify(myRows.myRows[i].type).replace('\"',' ').replace('\"',' ') +", <br>";
$('#sql').append(text);
}
var footer = ');';
$('#sql').append(footer);
});.parent {
display: grid;
grid-template-columns: repeat(10, 1fr);
grid-template-rows: repeat(12, 1fr);
grid-column-gap: 20px;
grid-row-gap: 0px;
}
.div1 { grid-area: 1 / 2 / 2 / 11; }
.div2 { grid-area: 5 / 6 / 6 / 7; }
.div3 { grid-area: 3 / 1 / 5 / 12; }
.div4 { grid-area: 2 / 1 / 3 / 2; }
.div5 { grid-area: 6 / 1 / 13 / 4; }
.div6 { grid-area: 6 / 4 / 13 / 8; }
.div7 { grid-area: 6 / 8 / 13 / 12; }
.div6 , .div7{
border: 1px solid black;
margin-right: 10px;
}
#btn1{
margin-bottom: 30px;
}<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title></title>
<script src="https://code.jquery.com/jquery-3.4.1.js" integrity="sha256-WpOohJOqMqqyKL9FccASB9O0KwACQJpFTUBLTYOVvVU=" crossorigin="anonymous"> </script>
<link href="https://stackpath.bootstrapcdn.com/bootstrap/4.4.1/css/bootstrap.min.css" rel="stylesheet" integrity="sha384-Vkoo8x4CGsO3+Hhxv8T/Q5PaXtkKtu6ug5TOeNV6gBiFeWPGFN9MuhOf23Q9Ifjh" crossorigin="anonymous">
</head>
<body>
<h2>Insert the text and the separator and press the button: </h2>
<div class="parent">
<div class="div1"></div>
<div class="div2 btn btn-alert"></div>
<div class="div3">
<textarea name="text" id="text" cols="120" rows="4" placeholder="ColummnName1,ColummName2,ColummName3,ColummName4,............"></textarea>
<input type="button" value="Convert to Table" id="btn1" class="btn btn-primary">
</div>
<div class="div4">Separatetor<input type="text" name="sep" id="sep" value=","> </div>
<div class="div5">
<input type="button" value="Convert to Avro" class="btn btn-success" id="btn2">
<input type="button" value="Convert to SQL Create" class="btn btn-info" id="btn3">
<div id="table"></div>
</div>
<div class="div6 card">
<div class="card-header font-weight-bolder">Avro Format</div>
<div class="card-body" id='avro'>
</div>
</div>
<div class="div7 card">
<div class="card-header font-weight-bolder">SQL Create</div>
<div class="card-body" id='sql'>
</div>
</div>
</div>
</body>
</html>