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RSS订阅原创 从0到1实现IOC
我们先来看看spring官网对IOC的定义：injectspattern.就不逐句翻译了，主要意思就是，IOC也被称为依赖注入，它是一个容器创建bean时将依赖对象注入的过程，而这些依赖对象在该bean中仅仅通过构造参数、工厂方法的参数或属性来指定。控制反转（Inversion of Control，缩写为IoC），是面向对象编程中的一种设计原则，可以用来减低代码之间的耦合度,提高代码的可重用性和可维护性。
2023-06-05 14:47:53
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翻译 Apache PDFBox - A Java PDF Library
The Apache PDFBox® library is an open source Java tool for working with PDF documents. This project allows creation of new PDF documents, manipulation of existing documents and the ability to extract content from documents. Apache PDFBox also includes seve
2022-03-31 16:18:41
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原创 What Is An NFT? Non-Fungible Tokens Explained
Non-fungible tokens (NFTs) seem to have exploded out of the ether this year. From art and music to tacos and toilet paper, these digital assets are selling like 17th-centuryexotic Dutch tulips—some for millions of dollars.今年，不可替代币（NFTs）似乎已经爆发了。从艺术和音乐到墨西.
2022-03-10 21:12:36
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翻译 20.2 Document Store Concepts
This section explains the concepts introduced as part of using MySQL as a document store.本节解释了将MySQL用作文档存储时引入的概念。 JSON Document Collection CRUD Operations JSON DocumentA JSON document is a data structure composed of key-value pairs and i
2022-03-10 16:43:01
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翻译 13.5 Prepared Statements
MySQL 8.0 provides support for server-side prepared statements. This support takes advantage of the efficient client/server binary protocol. Using prepared statements with placeholders for parameter values has the following benefits:MySQL 8.0支持服务器端prepar
2022-02-17 11:32:56
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翻译 20.4.1 MySQL Shell
This quick-start guide assumes a certain level of familiarity with MySQL Shell. The following section is a high level overview, see the MySQL Shell documentation for more information. MySQL Shell is a unified scripting interface to MySQL Server. It support
2021-12-21 23:20:21
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翻译 8.8.1 Optimizing Queries with EXPLAIN
TheEXPLAINstatement provides information about how MySQL executes statements:EXPLAIN语句提供有关MySQL如何执行语句的信息： EXPLAINworks withSELECT,DELETE,INSERT,REPLACE, andUPDATEstatements. EXPLAIN与SELECT、DELETE、INSERT、REPLACE和UPDATE语句一起协作 WhenEXP...
2021-12-08 23:02:03
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翻译 14.2 Transactional JDBC Access
Spring allows us to add transactions into our code without having to deal directly with the JDBC classes. For that purpose, Spring provides a transaction management package that not only replaces JDBC transaction management, but also enables declarative tr
2021-12-01 23:12:56
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翻译 8.2.1.3 Index Merge Optimization
TheIndex Mergeaccess method retrieves rows with multiplerangescans and merges their results into one. This access method merges index scans from a single table only, not scans across multiple tables. The merge can produce unions, intersections, or unio...
2021-09-30 11:45:07
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翻译 8.2.1.1 WHERE Clause Optimization
This section discusses optimizations that can be made for processingWHEREclauses. The examples useSELECTstatements, but the same optimizations apply forWHEREclauses inDELETEandUPDATEstatements.本篇讨论关于WHERE从句优化方面的内容，虽然例子是用SELECT 语句，但是这个优化同样适用于DEL...
2021-09-13 20:32:36
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翻译 8.3.14 Indexed Lookups from TIMESTAMP Columns
Temporal values are stored inTIMESTAMPcolumns as UTC values, and values inserted into and retrieved fromTIMESTAMPcolumns are converted between the session time zone and UTC. (This is the same type of conversion performed by theCONVERT_TZ()function. I...
2021-09-07 20:59:59
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翻译 8.3.13 Descending Indexes
MySQL supports descending indexes:DESCin an index definition is no longer ignored but causes storage of key values in descending order. Previously, indexes could be scanned in reverse order but at a performance penalty. A descending index can be scanned ..
2021-09-03 11:45:59
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翻译 8.3.12 Invisible Indexes
MySQL supports invisible indexes; that is, indexes that are not used by the optimizer. The feature applies to indexes other than primary keys (either explicit or implicit).Indexes are visible by default. To control visibility explicitly for a new index,
2021-08-30 17:50:54
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翻译 8.3.11 Optimizer Use of Generated Column Indexes
MySQL supports indexes on generated columns. For example:MySQL支撑在如下的列上建立索引：CREATE TABLE t1 (f1 INT, gc INT AS (f1 + 1) STORED, INDEX (gc));The generated column,gc, is defined as the expressionf1 + 1. The column is also indexed and the optimizer ca..
2021-08-27 17:48:25
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翻译 8.3.10 Use of Index Extensions
InnoDBautomatically extends each secondary index by appending the primary key columns to it. Consider this table definition:InnoDB通过自动在每个二级索引后面跟上主键列，比如下面这张表CREATE TABLE t1 ( i1 INT NOT NULL DEFAULT 0, i2 INT NOT NULL DEFAULT 0, d DATE DEFAULT N.
2021-08-22 22:17:07
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翻译 8.3.9 Comparison of B-Tree and Hash Indexes
Storage engines collect statistics about tables for use by the optimizer. Table statistics are based on value groups, where a value group is a set of rows with the same key prefix value. For optimizer purposes, an important statistic is the average value g
2021-08-22 21:26:38
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翻译 8.3.6 Multiple-Column Indexes
MySQL can create composite indexes (that is, indexes on multiple columns). An index may consist of up to 16 columns. For certain data types, you can index a prefix of the column (seeSection8.3.5, “Column Indexes”).MySQL can use multiple-column indexes ..
2021-08-16 17:16:55
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翻译 8.3.5 Column Indexes
The most common type of index involves a single column, storing copies of the values from that column in a data structure, allowing fast lookups for the rows with the corresponding column values. The B-tree data structure lets the index quickly find a spec
2021-08-15 21:00:41
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翻译 8.3.4 Foreign Key Optimization
If a table has many columns, and you query many different combinations of columns, it might be efficient to split the less-frequently used data into separate tables with a few columns each, and relate them back to the main table by duplicating the numeric
2021-08-09 21:27:11
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翻译 8.3.3 SPATIAL Index Optimization
MySQL permits creation ofSPATIALindexes onNOT NULLgeometry-valued columns (seeSection11.4.10, “Creating Spatial Indexes”). The optimizer checks theSRIDattribute for indexed columns to determine which spatial reference system (SRS) to use for compar...
2021-08-08 18:02:51
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翻译 8.3.2 Primary Key Optimization
The primary key for a table represents the column or set of columns that you use in your most vital queries. It has an associated index, for fast query performance. Query performance benefits from theNOT NULLoptimization, because it cannot include anyNU...
2021-08-08 16:40:28
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翻译 6.6. Query by Example 利用Example查询
6.6.1. IntroductionThis chapter provides an introduction to Query by Example and explains how to use it.Query by Example (QBE) is a user-friendly querying technique with a simple interface. It allows dynamic query creation and does not require you to wri
2021-08-05 20:36:16
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翻译 MYSQL8 8.3优化与索引
在测试中发现，对select 语句提升性能的最好方式是在其查询条件的一列或多列上增加索引。索引的行为如同指针一样，能够快速决定哪些数据行符合查询条件，并且所有的数据类型都可以增加索引。虽然为每个查询条件中的列都增加索引很有诱惑力，但是不必要的索引会浪费空间和时间（MYSQL需要确定用哪个索引），索引还会增加增、删、改的成本，因为每个索引都需要更新，所以我们必须建立最优的索引。8.3.1 怎么使用MYSQL索引索引通常被用于可以快速查询到数据的列值上。如果没有索引MYSQL必须从第一行开始，查询整个表
2021-06-26 21:13:38
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原创 springboot2 h2实现
这里写自定义目录标题1、配置ssl：C:\Program Files\Java\jdk1.8.0_201\bin>keytool -genkeypair -alias “tomcat” -keyalg “RSA” -keystore “e:\h2.keystore”2、开启支撑H2server: http2: enabled: true #开启支持h2 #ssl ssl: key-alias: tomcat #证书密码 key-password: ****** #证书
2021-01-28 19:22:07
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原创 Properties类介绍
1、继承与hashtable,效率比较低，理论上可以继承concurrentHashmap了2、键值对存储，对各种分隔符换行，空格有做处理
2019-08-26 22:21:09
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原创 Unable to locate Spring NamespaceHandler for XML schema namespace [http://shardingsphere.apache.org
Unable to locate Spring NamespaceHandler for XML schema namespace [http://shardingsphere.apache.org/schema/shardingsphere/sharding]增加配置<dependency> <groupId>io.shardingsphere&l...
2019-06-04 21:35:49
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原创 form中button提交表单
发现：springmvc 项目，js校验不通过，return后，表单依然可以提交。原因：form表单下的按钮在没有指定type类型的时候，如果我们同时给其添加了点击事件的话。会发现我们在点击的时候回默认的把表单也给提交了https://www.w3.org/TR/2011/WD-html5-20110525/the-button-element.html#attr-button-type...
2019-05-11 09:55:46
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原创 RESTful介绍
REST这个词，是Roy Thomas Fielding在他2000年的博士论文中提出的。他是HTTP协议（1.0版和1.1版）的主要设计者、Apache服务器软件的作者之一、Apache基金会的第一任主席。所以，他的这篇论文一经发表，就引起了关注，并且立即对互联网开发产生了深远的影响。他这样介绍他的写作目的：“”我这篇文章的写作目的，就是想在符合架构原理的前提下，理解和评估以网络为基础的应用...
2019-03-30 14:12:18
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原创 tomcat启动很慢
1、环境tomcat7 jdk8 启动web程序很慢。修改方法见https://blog.csdn.net/qq_34664963/article/details/790952632、debug慢但是run比较快，查看是否有断点，去掉所有断点即可。...
2019-03-14 16:00:25
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原创 rabbit mq中的坑，消费端错误造成的死循环
周五上线pre，发现mq消费端的调用的一个服务不停的报错，很快就把磁盘空间打满了，一开始以为是job死循环，当时确实也发现循环处有问题，修正循环处后，重新发布到pre环境发现还是有同样的问题，此时感觉很痛苦。通过仔细查看错误日志发现错误处是由rabbitmq 消费端报出来了，一时没有明白是什么原因，随找rabbitmq管理员，管理员说有消息一直没有消费掉，rabbitmq会一直重复投送消息，这样导...
2019-03-11 10:15:50
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原创 mysql unsign问题
在mysql中有mysql自己的特别之处，可以设置sql_model:STRICT_TRANS_TABLES, 此时数据类型int、decimal 的unsign标志就会起到校验作用，当为负值时，就会报错,错误码: 1264 ,内容：Out of range value for column 'num' at row 1。设置sql_model模式请见网上其他博客。...
2019-02-02 15:23:16
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原创 jquery checkbox table列表，最多选中两个，最少选中一个
$('input[name=groupCheckBox]').click(function(){ if($(this).parent().find("input[name='groupCheckBox']:checked").length >= 3) { $(this).removeAttr("checked"); alert("图片雕刻行最多选择两个分组!") ...
2018-04-20 15:42:25
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原创 quartz-源码理解第二天
1、quartz源码底层，是使用wait、notifyAll来处理的。所以先要理解清楚wait和notify才可以哦。先来一个面试常问到的问题：wait和sleep对比，对于两者，简而言之sleep是Thread(线程)静态方法，线程阻塞不释放获取的锁；waits 是Object的方法，同样会阻塞线程，但是同时会释放锁。wait的线程被唤醒有以下场景：a、别的线程调用该对象的notify/all;...
2018-03-31 14:32:16
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原创 ES 高亮显示
1、java部分,和其他网帖一样，不详细记录，大致如下：getClient().prepareSearch(getIndexAlias()).setTypes(getIndexType()).addHighlightedField("")SearchHit[] searchHits = response.getHits().getHits();if (highlightFields != null...
2018-03-27 14:59:47
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原创 quartz-源码理解第一天 -- 源码部署
1、到github上下载quartz源码，https://github.com/quartz-scheduler/quartz。选择自己想要的分支，这里选择quartz-2.2.x这个分支。 2、通过IDEA以maven工程方式导入的workspace中，导入后的目录如上图。此时可能报编译错误，此时要注意自己maven仓库，由于本地仓库jar不全，是用了阿里镜像仓库，才可以的，如下。<m...
2018-03-22 15:39:42
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原创 js onClick 方法 undefined
解决方法：onclick方法不能单独放置在用户的js脚本里面，可以放置在页面中用的形式，可以解决这个问题另外付jquery 动态增加删除表行 function delLaserPicRow(r){ alert("--del-"+r); if(confirm("确定删除?")){ $(r).paren
2017-08-30 20:09:44
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原创 域名备案
经过几个月，网站终于搞出来了，也部署到服务器上了。但是今天申请备案后，收到阿里云的客服电话，说个人备案不能随便取网站名字，只能是：xxxx的个人网站，或这个XXX的个人博客，还是真实姓名，问他是根据什么条例，说是江苏省网管局的条例，死活就是不让过，就这么把审批拒了。日了鬼了，还搞个屁的网站啊
2017-05-25 13:32:20
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求DB2 大量数据的归档方案
2015-09-10
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