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java 读取mysql blob字段乱码

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版权声明：有时疏忽导致文章出现纰漏, 添加转载引用助于及时修改源头的错误 https://blog.csdn.net/qq_34208844/article/details/86503754 场景使用java作为后端操作数据库, 插入的时候是好的(数据库也显示的中文), 但是查询出来的时候就变成乱码了… 分析同一条数据, 别的字段的中文存取都是正常的, 唯独这个 blob 格式的字段存进去中文, 取出来就变成乱码了原因 blob 存储的是二进制格式, 最大好像支持到2g 如果存储的是存文本的话可以使用 text 格式解决方案方案一: 修改格式修改数据库字段格式, 将 blob 字段格式改为 text 的格式方案二: 转换字符编码在java 代码中将字符编码手动转换 blob = new String ( blob . getBytes ( CharsetNames . ISO_8859_1 ) , CharsetNames . UTF_8 ) 文章来源: https://blog.csdn.net/qq_34208844/article/details/86503754

前端js 实现文件下载

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https://www.zhangxinxu.com/wordpress/2017/07/js-text-string-download-as-html-json-file/ 侵删 1.H5 download属性 function downFile(content, filename) { // 创建隐藏的可下载链接 var eleLink = document.createElement('a'); eleLink.download = filename; eleLink.style.display = 'none'; // 字符内容转变成blob地址 var blob = new Blob([content]); eleLink.href = URL.createObjectURL(blob); // 触发点击 document.body.appendChild(eleLink); eleLink.click(); // 然后移除 document.body.removeChild(eleLink); }; downFile(下载地址, 保存名称); 2.iframe方式 // if (typeof(download.iframe) == 'undefined') { // var iframe = document.createElement('iframe'); //

JavaScript前端图片压缩

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实现思路获取input的file 使用fileReader() 将图片转为base64 使用canvas读取base64 并降低分辨率把canvas数据转成blob对象把blob对象转file对象完成压缩相关代码： <!doctype html> <html lang="en"> <head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0"> <meta http-equiv="X-UA-Compatible" content="ie=edge"> <title>Document</title> </head> <body> <input type="file" id="file"> <script> document.getElementById('file').addEventListener('change',function (e) { let fileObj = e.target.files[0] let that = this; compressFile(fileObj,function (files) {

Inserting Large Object into Postgresql returns 53200 Out of Memory error

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问题 Postgresql 9.1 NPGSQL 2.0.12 I have binary data I am wanting to store in a postgresql database. Most files load fine, however, a large binary (664 Mb) file is causing problems. When trying to load the file to postgresql using Large Object support through Npgsql, the postgresql server returns 'out of memory' error. I'm running this at present on a workstation with 4Gb RAM, with 2Gb free with postgresql running in an idle state. This is the code I am using, adapted from PG Foundry Npgsql User's

Huge JavaScript HTML5 blob (from large ArrayBuffers) to build a giant file in client side

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I'm writing a web browser app (client-side) that downloads a huge amount of chunks from many locations and joins them to build a blob. Then that blob is saved to local filesystem as a common file. The way I'm doing this is by mean of ArrayBuffer objects and a blob. var blob = new Blob([ArrayBuffer1, ArrayBuffer2, ArrayBuffer3, ...], {type: mimetype}) This works ok for small and medium-sized files (until 700 MB aprox), but browser crashes with larger files. I understand that RAM memory has its limits. The case is that I need to build the blob in order to generate a file, but I wanna allow users

How can I insert into a BLOB column from an insert statement in sqldeveloper?

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Is it possible to insert into a BLOB column in oracle using sqldeveloper? i.e. something like: insert into mytable(id, myblob) values (1,'some magic here'); Yes, it's possible, e.g. using the implicit conversion from RAW to BLOB: insert into blob_fun values(1, hextoraw('453d7a34')); 453d7a34 is a string of hexadecimal values, which is first explicitly converted to the RAW data type and then inserted into the BLOB column. The result is a BLOB value of 4 bytes. To insert a VARCHAR2 into a BLOB column you can rely on the function utl_raw.cast_to_raw as next: insert into mytable(id, myblob) values

uploading images to server in spring MVC and storing reference in mysql database [closed]

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As it currently stands, this question is not a good fit for our Q&A format. We expect answers to be supported by facts, references, or expertise, but this question will likely solicit debate, arguments, polling, or extended discussion. If you feel that this question can be improved and possibly reopened, visit the help center for guidance. I'm coding a Spring MVC 3.0 application with Tomcat as the web server. Our requirement is to let the user upload an image. I'm thinking of storing this image on the disk file system and store the reference path in MySQL instead of storing all the file info

数据库的类型

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MySQL支持多种类型，大致可以分为三类：数值、日期/时间和字符串(字符)类型。根据数值取值范围的不同，MySQL中的整数类型可分为5种，分别是TINYINT、SMALLINT、MEDIUMINT、INT和BIGINT。一、整数类型数据类型字节数无符号数的取值范围有符号数的取值范围 TINYINT 1 0~255 -128~127 SMALLINT 2 0~65535 -32768~32768 MEDIUMINT 3 0~16777215 -8388608~8388608 INT 4 0~4294967295 -2147483648~2147483648 BIGINT 8 0~18446744073709551615 -9223372036854775808~9223372036854775808 二、浮点型类型和定点数类型三、数据类型字节数有符号的取值范围无符号的取值范围 FLOAT 4 -3.402823466E+38~ -1.175494351E-38 0和1.175494351E-38~ 3.402823466E+38 DOUBLE 4 -1.7976931348623157E+308~ 2.2250738585072014E-308 0和2.2250738585072014E-308~ 1.7976931348623157E+308 DECIMAL

Parallel.js have problems with Blob in IE

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问题 I need to execute functions in "parallel" and I use parallel.js : var p = new Parallel(items); var fn1 = function (item) { doSomething(item); }; p.map(fn1).then(function () { otherFunction(); }); But IE shows the following error: [Q] Unhandled rejection reasons (should be empty): (no stack) SecurityError HTML7007: One or more blob URLs were revoked by closing the blob for which they were created. These URLs will no longer resolve as the data backing the URL has been freed. How to fix this

How to write java.sql.Blob to JPA entity?

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I have a JPA entity with java.sql.Blob: @Entity public class LargeData { @Lob private java.sql.Blob data; //getters/setters } How to create instance of this entity? I want to set Blob with setData() method, but how to get Blob from JPA? java.sql.Blob is only interface, there are different implementations for different databases, so I assume JPA should give me right implementation. How to get it? Use a byte array: @Lob @Column(length=100000) private byte[] data; If you want to use streams, create the blob using Hibernate.createBlob(..) use a file stream. However, this appears to have various

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