12.3.3.13 Try-catch statements

博客介绍了try-catch语句中变量的确定赋值状态。对于特定形式的try-catch语句,try块开始时变量v的赋值状态与语句开始时相同,每个catch块开始时v的赋值状态也如此。语句结束点v被确定赋值的条件是try块和所有catch块结束点v都被确定赋值。
12.3.3.13 Try-catch statements
For a statement stmt of the form:
try try-block
catch(.) catch-block-1
.
catch(.) catch-block-n
. The definite assignment state of v at the beginning of try-block is the
same as the definite
assignment state of v at the beginning of stmt.
. The definite assignment state of v at the beginning of catch-block-i (for
any i) is the same as the
definite assignment state of v at the beginning of stmt.
. The definite assignment state of v at the end-point of stmt is definitely
assigned if (and only if) v is
definitely assigned at the end-point of try-block and every catch-block-i
(for every i from 1 to n).
**项目名称:** 基于Vue.js与Spring Cloud架构的博客系统设计与开发——微服务分布式应用实践 **项目概述:** 本项目为计算机科学与技术专业本科毕业设计成果,旨在设计并实现一个采用前后端分离架构的现代化博客平台。系统前端基于Vue.js框架构建,提供响应式用户界面;后端采用Spring Cloud微服务架构,通过服务拆分、注册发现、配置中心及网关路由等技术,构建高可用、易扩展的分布式应用体系。项目重点探讨微服务模式下的系统设计、服务治理、数据一致性及部署运维等关键问题,体现了分布式系统在Web应用中的实践价值。 **技术架构:** 1. **前端技术栈:** Vue.js 2.x、Vue Router、Vuex、Element UI、Axios 2. **后端技术栈:** Spring Boot 2.x、Spring Cloud (Eureka/Nacos、Feign/OpenFeign、Ribbon、Hystrix、Zuul/Gateway、Config) 3. **数据存储:** MySQL 8.0(主数据存储)、Redis(缓存与会话管理) 4. **服务通信:** RESTful API、消息队列(可选RabbitMQ/Kafka) 5. **部署与运维:** Docker容器化、Jenkins持续集成、Nginx负载均衡 **核心功能模块:** - 用户管理:注册登录、权限控制、个人中心 - 文章管理:富文本编辑、分类标签、发布审核、评论互动 - 内容展示:首页推荐、分类检索、全文搜索、热门排行 - 系统管理:后台仪表盘、用户与内容监控、日志审计 - 微服务治理:服务健康检测、动态配置更新、熔断降级策略 **设计特点:** 1. **架构解耦:** 前后端完全分离,通过API网关统一接入,支持独立开发与部署。 2. **服务拆分:** 按业务域划分为用户服务、文章服务、评论服务、文件服务等独立微服务。 3. **高可用设计:** 采用服务注册发现机制,配合负载均衡与熔断器,提升系统容错能力。 4. **可扩展性:** 模块化设计支持横向扩展,配置中心实现运行时动态调整。 **项目成果:** 完成了一个具备完整博客功能、具备微服务典型特征的分布式系统原型,通过容器化部署验证了多服务协同运行的可行性,为云原生应用开发提供了实践参考。 资源来源于网络分享,仅用于学习交流使用,请勿用于商业,如有侵权请联系我删除!
mysql Ver 14.14 Distrib 5.7.18, for Win64 (x86_64) Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved. Oracle is a registered trademark of Oracle Corporation and/or its affiliates. Other names may be trademarks of their respective owners. Usage: mysql [OPTIONS] [database] -?, --help Display this help and exit. -I, --help Synonym for -? --auto-rehash Enable automatic rehashing. One doesn't need to use 'rehash' to get table and field completion, but startup and reconnecting may take a longer time. Disable with --disable-auto-rehash. (Defaults to on; use --skip-auto-rehash to disable.) -A, --no-auto-rehash No automatic rehashing. One has to use 'rehash' to get table and field completion. This gives a quicker start of mysql and disables rehashing on reconnect. --auto-vertical-output Automatically switch to vertical output mode if the result is wider than the terminal width. -B, --batch Don't use history file. Disable interactive behavior. (Enables --silent.) --bind-address=name IP address to bind to. --character-sets-dir=name Directory for character set files. --column-type-info Display column type information. -c, --comments Preserve comments. Send comments to the server. The default is --skip-comments (discard comments), enable with --comments. -C, --compress Use compression in server/client protocol. -#, --debug[=#] This is a non-debug version. Catch this and exit. --debug-check This is a non-debug version. Catch this and exit. -T, --debug-info This is a non-debug version. Catch this and exit. -D, --database=name Database to use. --default-character-set=name Set the default character set. --delimiter=name Delimiter to be used. --enable-cleartext-plugin Enable/disable the clear text authentication plugin. -e, --execute=name Execute command and quit. (Disables --force and history file.) -E, --vertical Print the output of a query (rows) vertically. -f, --force Continue even if we get an SQL error. --histignore=name A colon-separated list of patterns to keep statements from getting logged into syslog and mysql history. -G, --named-commands Enable named commands. Named commands mean this program's internal commands; see mysql> help . When enabled, the named commands can be used from any line of the query, otherwise only from the first line, before an enter. Disable with --disable-named-commands. This option is disabled by default. -i, --ignore-spaces Ignore space after function names. --init-command=name SQL Command to execute when connecting to MySQL server. Will automatically be re-executed when reconnecting. --local-infile Enable/disable LOAD DATA LOCAL INFILE. -b, --no-beep Turn off beep on error. -h, --host=name Connect to host. -H, --html Produce HTML output. -X, --xml Produce XML output. --line-numbers Write line numbers for errors. (Defaults to on; use --skip-line-numbers to disable.) -L, --skip-line-numbers Don't write line number for errors. -n, --unbuffered Flush buffer after each query. --column-names Write column names in results. (Defaults to on; use --skip-column-names to disable.) -N, --skip-column-names Don't write column names in results. --sigint-ignore Ignore SIGINT (CTRL-C). -o, --one-database Ignore statements except those that occur while the default database is the one named at the command line. -p, --password[=name] Password to use when connecting to server. If password is not given it's asked from the tty. -W, --pipe Use named pipes to connect to server. -P, --port=# Port number to use for connection or 0 for default to, in order of preference, my.cnf, $MYSQL_TCP_PORT, /etc/services, built-in default (3306). --prompt=name Set the mysql prompt to this value. --protocol=name The protocol to use for connection (tcp, socket, pipe, memory). -q, --quick Don't cache result, print it row by row. This may slow down the server if the output is suspended. Doesn't use history file. -r, --raw Write fields without conversion. Used with --batch. --reconnect Reconnect if the connection is lost. Disable with --disable-reconnect. This option is enabled by default. (Defaults to on; use --skip-reconnect to disable.) -s, --silent Be more silent. Print results with a tab as separator, each row on new line. --shared-memory-base-name=name Base name of shared memory. -S, --socket=name The socket file to use for connection. --ssl-mode=name SSL connection mode. --ssl Deprecated. Use --ssl-mode instead. (Defaults to on; use --skip-ssl to disable.) --ssl-verify-server-cert Deprecated. Use --ssl-mode=VERIFY_IDENTITY instead. --ssl-ca=name CA file in PEM format. --ssl-capath=name CA directory. --ssl-cert=name X509 cert in PEM format. --ssl-cipher=name SSL cipher to use. --ssl-key=name X509 key in PEM format. --ssl-crl=name Certificate revocation list. --ssl-crlpath=name Certificate revocation list path. --tls-version=name TLS version to use, permitted values are: TLSv1, TLSv1.1 -t, --table Output in table format. --tee=name Append everything into outfile. See interactive help (\h) also. Does not work in batch mode. Disable with --disable-tee. This option is disabled by default. -u, --user=name User for login if not current user. -U, --safe-updates Only allow UPDATE and DELETE that uses keys. -U, --i-am-a-dummy Synonym for option --safe-updates, -U. -v, --verbose Write more. (-v -v -v gives the table output format). -V, --version Output version information and exit. -w, --wait Wait and retry if connection is down. --connect-timeout=# Number of seconds before connection timeout. --max-allowed-packet=# The maximum packet length to send to or receive from server. --net-buffer-length=# The buffer size for TCP/IP and socket communication. --select-limit=# Automatic limit for SELECT when using --safe-updates. --max-join-size=# Automatic limit for rows in a join when using --safe-updates. --secure-auth Refuse client connecting to server if it uses old (pre-4.1.1) protocol. Deprecated. Always TRUE --server-arg=name Send embedded server this as a parameter. --show-warnings Show warnings after every statement. -j, --syslog Log filtered interactive commands to syslog. Filtering of commands depends on the patterns supplied via histignore option besides the default patterns. --plugin-dir=name Directory for client-side plugins. --default-auth=name Default authentication client-side plugin to use. --binary-mode By default, ASCII '\0' is disallowed and '\r\n' is translated to '\n'. This switch turns off both features, and also turns off parsing of all clientcommands except \C and DELIMITER, in non-interactive mode (for input piped to mysql or loaded using the 'source' command). This is necessary when processing output from mysqlbinlog that may contain blobs. --connect-expired-password Notify the server that this client is prepared to handle expired password sandbox mode. Default options are read from the following files in the given order: C:\WINDOWS\my.ini C:\WINDOWS\my.cnf C:\my.ini C:\my.cnf D:\mysql\mysql-5.7.18-winx64\mysql-5.7.18-winx64\my.ini D:\mysql\mysql-5.7.18-winx64\mysql-5.7.18-winx64\my.cnf The following groups are read: mysql client The following options may be given as the first argument: --print-defaults Print the program argument list and exit. --no-defaults Don't read default options from any option file, except for login file. --defaults-file=# Only read default options from the given file #. --defaults-extra-file=# Read this file after the global files are read. --defaults-group-suffix=# Also read groups with concat(group, suffix) --login-path=# Read this path from the login file. Variables (--variable-name=value) and boolean options {FALSE|TRUE} Value (after reading options) --------------------------------- ---------------------------------------- auto-rehash TRUE auto-vertical-output FALSE bind-address (No default value) character-sets-dir (No default value) column-type-info FALSE comments FALSE compress FALSE database (No default value) default-character-set utf8 delimiter ; enable-cleartext-plugin FALSE vertical FALSE force FALSE histignore (No default value) named-commands FALSE ignore-spaces FALSE init-command (No default value) local-infile FALSE no-beep FALSE host (No default value) html FALSE xml FALSE line-numbers TRUE unbuffered FALSE column-names TRUE sigint-ignore FALSE port 3306 prompt mysql> quick FALSE raw FALSE reconnect TRUE shared-memory-base-name (No default value) socket (No default value) ssl TRUE ssl-verify-server-cert FALSE ssl-ca (No default value) ssl-capath (No default value) ssl-cert (No default value) ssl-cipher (No default value) ssl-key (No default value) ssl-crl (No default value) ssl-crlpath (No default value) tls-version (No default value) table FALSE user (No default value) safe-updates FALSE i-am-a-dummy FALSE connect-timeout 0 max-allowed-packet 16777216 net-buffer-length 16384 select-limit 1000 max-join-size 1000000 secure-auth TRUE show-warnings FALSE plugin-dir (No default value) default-auth (No default value) binary-mode FALSE connect-expired-password FALSE C:\Users\lenovo>mysql –u root –p mysql Ver 14.14 Distrib 5.7.18, for Win64 (x86_64) Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved. Oracle is a registered trademark of Oracle Corporation and/or its affiliates. Other names may be trademarks of their respective owners. Usage: mysql [OPTIONS] [database] -?, --help Display this help and exit. -I, --help Synonym for -? --auto-rehash Enable automatic rehashing. One doesn't need to use 'rehash' to get table and field completion, but startup and reconnecting may take a longer time. Disable with --disable-auto-rehash. (Defaults to on; use --skip-auto-rehash to disable.) -A, --no-auto-rehash No automatic rehashing. One has to use 'rehash' to get table and field completion. This gives a quicker start of mysql and disables rehashing on reconnect. --auto-vertical-output Automatically switch to vertical output mode if the result is wider than the terminal width. -B, --batch Don't use history file. Disable interactive behavior. (Enables --silent.) --bind-address=name IP address to bind to. --character-sets-dir=name Directory for character set files. --column-type-info Display column type information. -c, --comments Preserve comments. Send comments to the server. The default is --skip-comments (discard comments), enable with --comments. -C, --compress Use compression in server/client protocol. -#, --debug[=#] This is a non-debug version. Catch this and exit. --debug-check This is a non-debug version. Catch this and exit. -T, --debug-info This is a non-debug version. Catch this and exit. -D, --database=name Database to use. --default-character-set=name Set the default character set. --delimiter=name Delimiter to be used. --enable-cleartext-plugin Enable/disable the clear text authentication plugin. -e, --execute=name Execute command and quit. (Disables --force and history file.) -E, --vertical Print the output of a query (rows) vertically. -f, --force Continue even if we get an SQL error. --histignore=name A colon-separated list of patterns to keep statements from getting logged into syslog and mysql history. -G, --named-commands Enable named commands. Named commands mean this program's internal commands; see mysql> help . When enabled, the named commands can be used from any line of the query, otherwise only from the first line, before an enter. Disable with --disable-named-commands. This option is disabled by default. -i, --ignore-spaces Ignore space after function names. --init-command=name SQL Command to execute when connecting to MySQL server. Will automatically be re-executed when reconnecting. --local-infile Enable/disable LOAD DATA LOCAL INFILE. -b, --no-beep Turn off beep on error. -h, --host=name Connect to host. -H, --html Produce HTML output. -X, --xml Produce XML output. --line-numbers Write line numbers for errors. (Defaults to on; use --skip-line-numbers to disable.) -L, --skip-line-numbers Don't write line number for errors. -n, --unbuffered Flush buffer after each query. --column-names Write column names in results. (Defaults to on; use --skip-column-names to disable.) -N, --skip-column-names Don't write column names in results. --sigint-ignore Ignore SIGINT (CTRL-C). -o, --one-database Ignore statements except those that occur while the default database is the one named at the command line. -p, --password[=name] Password to use when connecting to server. If password is not given it's asked from the tty. -W, --pipe Use named pipes to connect to server. -P, --port=# Port number to use for connection or 0 for default to, in order of preference, my.cnf, $MYSQL_TCP_PORT, /etc/services, built-in default (3306). --prompt=name Set the mysql prompt to this value. --protocol=name The protocol to use for connection (tcp, socket, pipe, memory). -q, --quick Don't cache result, print it row by row. This may slow down the server if the output is suspended. Doesn't use history file. -r, --raw Write fields without conversion. Used with --batch. --reconnect Reconnect if the connection is lost. Disable with --disable-reconnect. This option is enabled by default. (Defaults to on; use --skip-reconnect to disable.) -s, --silent Be more silent. Print results with a tab as separator, each row on new line. --shared-memory-base-name=name Base name of shared memory. -S, --socket=name The socket file to use for connection. --ssl-mode=name SSL connection mode. --ssl Deprecated. Use --ssl-mode instead. (Defaults to on; use --skip-ssl to disable.) --ssl-verify-server-cert Deprecated. Use --ssl-mode=VERIFY_IDENTITY instead. --ssl-ca=name CA file in PEM format. --ssl-capath=name CA directory. --ssl-cert=name X509 cert in PEM format. --ssl-cipher=name SSL cipher to use. --ssl-key=name X509 key in PEM format. --ssl-crl=name Certificate revocation list. --ssl-crlpath=name Certificate revocation list path. --tls-version=name TLS version to use, permitted values are: TLSv1, TLSv1.1 -t, --table Output in table format. --tee=name Append everything into outfile. See interactive help (\h) also. Does not work in batch mode. Disable with --disable-tee. This option is disabled by default. -u, --user=name User for login if not current user. -U, --safe-updates Only allow UPDATE and DELETE that uses keys. -U, --i-am-a-dummy Synonym for option --safe-updates, -U. -v, --verbose Write more. (-v -v -v gives the table output format). -V, --version Output version information and exit. -w, --wait Wait and retry if connection is down. --connect-timeout=# Number of seconds before connection timeout. --max-allowed-packet=# The maximum packet length to send to or receive from server. --net-buffer-length=# The buffer size for TCP/IP and socket communication. --select-limit=# Automatic limit for SELECT when using --safe-updates. --max-join-size=# Automatic limit for rows in a join when using --safe-updates. --secure-auth Refuse client connecting to server if it uses old (pre-4.1.1) protocol. Deprecated. Always TRUE --server-arg=name Send embedded server this as a parameter. --show-warnings Show warnings after every statement. -j, --syslog Log filtered interactive commands to syslog. Filtering of commands depends on the patterns supplied via histignore option besides the default patterns. --plugin-dir=name Directory for client-side plugins. --default-auth=name Default authentication client-side plugin to use. --binary-mode By default, ASCII '\0' is disallowed and '\r\n' is translated to '\n'. This switch turns off both features, and also turns off parsing of all clientcommands except \C and DELIMITER, in non-interactive mode (for input piped to mysql or loaded using the 'source' command). This is necessary when processing output from mysqlbinlog that may contain blobs. --connect-expired-password Notify the server that this client is prepared to handle expired password sandbox mode. Default options are read from the following files in the given order: C:\WINDOWS\my.ini C:\WINDOWS\my.cnf C:\my.ini C:\my.cnf D:\mysql\mysql-5.7.18-winx64\mysql-5.7.18-winx64\my.ini D:\mysql\mysql-5.7.18-winx64\mysql-5.7.18-winx64\my.cnf The following groups are read: mysql client The following options may be given as the first argument: --print-defaults Print the program argument list and exit. --no-defaults Don't read default options from any option file, except for login file. --defaults-file=# Only read default options from the given file #. --defaults-extra-file=# Read this file after the global files are read. --defaults-group-suffix=# Also read groups with concat(group, suffix) --login-path=# Read this path from the login file. Variables (--variable-name=value) and boolean options {FALSE|TRUE} Value (after reading options) --------------------------------- ---------------------------------------- auto-rehash TRUE auto-vertical-output FALSE bind-address (No default value) character-sets-dir (No default value) column-type-info FALSE comments FALSE compress FALSE database (No default value) default-character-set utf8 delimiter ; enable-cleartext-plugin FALSE vertical FALSE force FALSE histignore (No default value) named-commands FALSE ignore-spaces FALSE init-command (No default value) local-infile FALSE no-beep FALSE host (No default value) html FALSE xml FALSE line-numbers TRUE unbuffered FALSE column-names TRUE sigint-ignore FALSE port 3306 prompt mysql> quick FALSE raw FALSE reconnect TRUE shared-memory-base-name (No default value) socket (No default value) ssl TRUE ssl-verify-server-cert FALSE ssl-ca (No default value) ssl-capath (No default value) ssl-cert (No default value) ssl-cipher (No default value) ssl-key (No default value) ssl-crl (No default value) ssl-crlpath (No default value) tls-version (No default value) table FALSE user (No default value) safe-updates FALSE i-am-a-dummy FALSE connect-timeout 0 max-allowed-packet 16777216 net-buffer-length 16384 select-limit 1000 max-join-size 1000000 secure-auth TRUE show-warnings FALSE plugin-dir (No default value) default-auth (No default value) binary-mode FALSE connect-expired-password FALSE C:\Users\lenovo>
06-23
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