需求介绍：将mongodb中的数据以文件的方式导出：json或cvs格式
mongo 提供了mongoexport的工具，可以实现将库中的数据以json或cvs的格式输出到文件中。mongoexport位于mongo安装位置中的bin/目录下。
mongoexport具体用法如下所示：
1. 使用help查看参数说明
E:\data
λ mongoexport --help
Usage:
mongoexport <options>
Export data from MongoDB in CSV or JSON format.
See http://docs.mongodb.org/manual/reference/program/mongoexport/ for more information.
general options:
/help print usage
/version print the tool version and exit
verbosity options:
/v, /verbose more detailed log output (include multiple
times for more verbosity, e.g. -vvvvv)
/quiet hide all log output
connection options:
/h, /host: mongodb host to connect to
(setname/host1,host2 for replica sets)
/port: server port (can also use --host hostname:port)
authentication options:
/u, /username: username for authentication
/p, /password: password for authentication
/authenticationDatabase: database that holds the user's credentials
/authenticationMechanism: authentication mechanism to use
namespace options:
/d, /db: database to use
/c, /collection: collection to use
output options:
/f, /fields: comma separated list of field names (required
for exporting CSV) e.g. -f "name,age"
/fieldFile: file with field names - 1 per line
/type: the output format, either json or csv
(defaults to 'json')
/o, /out: output file; if not specified, stdout is used
/jsonArray output to a JSON array rather than one object
per line
/pretty output JSON formatted to be human-readable
querying options:
/q, /query: query filter, as a JSON string, e.g.,
'{x:{$gt:1}}'
/k, /slaveOk allow secondary reads if available (default
true)
/forceTableScan force a table scan (do not use $snapshot)
/skip: number of documents to skip
/limit: limit the number of documents to export
/sort: sort order, as a JSON string, e.g. '{x:1}'
2. 用例说明:
将info库中student的所有信息以json格式导出到student_json.dat数据文件中
mongoexport -h 127.0.0.1 -u root -p 12345 -d info -c student --type=json -o E:\data\student_json.dat
输出：
{
"id": 123,
"name": "张三",
"age": 12
}
{
"id": 124,
"name": "李四",
"age": 15
}
将info库中student的id,name信息以json格式导出到student_json.dat数据文件中，并且限定“行数”是1
mongoexport -h 127.0.0.1 -u root -p 12345 -d info -c student --type=json -f id,name --limit=1 -o E:\data\student_json.dat
输出：
{
"id": 1,
"name": "张三"
}
将info库中student的所有信息以cvs格式导出到student_cvs.dat数据文件中
mongoexport -h 127.0.0.1 -u root -p 12345 -d info -c student --type=cvs -o E:\data\student_cvs.dat
输出：
123,"张三",12 124,"李四",15
将info库student“表”的name=张三的信息以cvs格式导出到student_cvs.dat数据文件中
mongoexport -h 127.0.0.1 -u root -p 12345 -d info -c student --type=cvs -q{"name":"张三"} -o E:\data\student_cvs.dat
输出：
123,"张三",12
注意：
a. --type=json 只是控制每一条“记录”是json格式，而整体的输出文件不是json 。如果想要控制整体的文件数据格式是json数组，则需要使用--jsonArray 参数控制
扩展：
导入工具mongoimport
Mongodb中的mongoimport工具可以把一个特定格式文件中的内容导入到指定的collection中。该工具可以导入JSON格式数据，也可以导入CSV格式数据。具体使用如下所示：
E:\data
λ mongoimport --help
Usage:
mongoimport <options> <file>
Import CSV, TSV or JSON data into MongoDB. If no file is provided, mongoimport reads from stdin.
See http://docs.mongodb.org/manual/reference/program/mongoimport/ for more information.
general options:
/help print usage
/version print the tool version and exit
verbosity options:
/v, /verbose more detailed log output (include multiple
times for more verbosity, e.g. -vvvvv)
/quiet hide all log output
connection options:
/h, /host: mongodb host to connect to
(setname/host1,host2 for replica sets)
/port: server port (can also use --host hostname:port)
authentication options:
/u, /username: username for authentication
/p, /password: password for authentication
/authenticationDatabase: database that holds the user's credentials
/authenticationMechanism: authentication mechanism to use
namespace options:
/d, /db: database to use
/c, /collection: collection to use
input options:
/f, /fields: comma separated list of field names, e.g. -f
name,age
/fieldFile: file with field names - 1 per line
/file: file to import from; if not specified, stdin
is used
/headerline use first line in input source as the field
list (CSV and TSV only)
/jsonArray treat input source as a JSON array
/type: input format to import: json, csv, or tsv
(defaults to 'json')
ingest options:
/drop drop collection before inserting documents
/ignoreBlanks ignore fields with empty values in CSV and TSV
/maintainInsertionOrder insert documents in the order of their
appearance in the input source
/j, /numInsertionWorkers: number of insert operations to run
concurrently (defaults to 1)
/stopOnError stop importing at first insert/upsert error
/upsert insert or update objects that already exist
/upsertFields: comma-separated fields for the query part of
the upsert
/writeConcern: write concern options e.g. --writeConcern
majority, --writeConcern '{w: 3, wtimeout:
500, fsync: true, j: true}' (defaults to
'majority')
参数说明：
-h:指明数据库宿主机的IP
-u:指明数据库的用户名
-p:指明数据库的密码
-d:指明数据库的名字
-c:指明collection的名字
-f:指明要导入那些列
示例：先删除students中的数据，并验证
> db.students.remove()
> db.students.find()
>
然后再导入上面导出的students.dat文件中的内容
mongoimport -d test -c students students.dat
connected to: 127.0.0.1
imported 9 objects
参数说明：
-d:指明数据库名，本例中为test
-c:指明collection名，本例中为students
students.dat：导入的文件名
查询students集合中的数据
> db.students.find()
{ "_id" : ObjectId("5031143350f2481577ea81e5"), "classid" : 1, "age" : 20, "name" : "kobe" }
{ "_id" : ObjectId("5031144a50f2481577ea81e6"), "classid" : 1, "age" : 23, "name" : "nash" }
{ "_id" : ObjectId("5031145a50f2481577ea81e7"), "classid" : 2, "age" : 18, "name" : "james" }
{ "_id" : ObjectId("5031146a50f2481577ea81e8"), "classid" : 2, "age" : 19, "name" : "wade" }
{ "_id" : ObjectId("5031147450f2481577ea81e9"), "classid" : 2, "age" : 19, "name" : "bosh" }
{ "_id" : ObjectId("5031148650f2481577ea81ea"), "classid" : 2, "age" : 25, "name" : "allen" }
{ "_id" : ObjectId("5031149b50f2481577ea81eb"), "classid" : 1, "age" : 19, "name" : "howard" }
{ "_id" : ObjectId("503114a750f2481577ea81ec"), "classid" : 1, "age" : 22, "name" : "paul" }
{ "_id" : ObjectId("503114cd50f2481577ea81ed"), "classid" : 2, "age" : 24, "name" : "shane" }
>
证明数据导入成功
上面演示的是导入JSON格式的文件中的内容，如果要导入CSV格式文件中的内容，则需要通过--type参数指定导入格式，具体如下所示：
先删除数据
> db.students.remove()
> db.students.find()
>
再导入之前导出的students_csv.dat文件
mongoimport -d test -c students --type csv --headerline --file students_csv.dat
connected to: 127.0.0.1
imported 10 objects
参数说明：
-type:指明要导入的文件格式
-headerline:指明第一行是列名，不需要导入
-file：指明要导入的文件
查询students集合，验证导入是否成功：
> db.students.find()
{ "_id" : ObjectId("503266029355c632cd118ad8"), "classid" : 1, "name" : "kobe", "age" : 20 }
{ "_id" : ObjectId("503266029355c632cd118ad9"), "classid" : 1, "name" : "nash", "age" : 23 }
{ "_id" : ObjectId("503266029355c632cd118ada"), "classid" : 2, "name" : "james", "age" : 18 }
{ "_id" : ObjectId("503266029355c632cd118adb"), "classid" : 2, "name" : "wade", "age" : 19 }
{ "_id" : ObjectId("503266029355c632cd118adc"), "classid" : 2, "name" : "bosh", "age" : 19 }
{ "_id" : ObjectId("503266029355c632cd118add"), "classid" : 2, "name" : "allen", "age" : 25 }
{ "_id" : ObjectId("503266029355c632cd118ade"), "classid" : 1, "name" : "howard", "age" : 19 }
{ "_id" : ObjectId("503266029355c632cd118adf"), "classid" : 1, "name" : "paul", "age" : 22 }
{ "_id" : ObjectId("503266029355c632cd118ae0"), "classid" : 2, "name" : "shane", "age" : 24 }
>
说明已经导入成功
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