How to use IoT technology in Java to implement intelligent devices and systems?

Lazy loading only queries when accessing associations can easily lead to N 1 problems, which is suitable for scenarios where the associated data is not determined whether it is needed; 2. Emergency loading uses with() to load associated data in advance to avoid N 1 queries, which is suitable for batch processing scenarios; 3. Emergency loading should be used to optimize performance, and N 1 problems can be detected through tools such as LaravelDebugbar, and the $with attribute of the model is carefully used to avoid unnecessary performance overhead.

Python's memory management is based on reference counting and garbage collection mechanisms. 1. The reference counting mechanism ensures that objects are released immediately when the reference number is 0. The return value of sys.getrefcount() is 1 more than the actual reference because it increases its reference itself; 2. Circular references cannot be cleaned through reference counting, and it depends on the generational recycling of the gc module. Calling gc.collect() can recycle unreachable objects; 3. In actual development, long-term holding of large object references should be avoided. We can use weakref weak references, timely place None to release memory, and use tracemalloc to monitor memory allocation; 4. Summary: Python combines reference counting and garbage collection to manage memory, developers can use tools and optimize reference pipes.

UseaRESTAPItobridgePHPandMLmodelsbyrunningthemodelinPythonviaFlaskorFastAPIandcallingitfromPHPusingcURLorGuzzle.2.RunPythonscriptsdirectlyfromPHPusingexec()orshell_exec()forsimple,low-trafficusecases,thoughthisapproachhassecurityandperformancelimitat

Laravel supports the use of native SQL queries, but parameter binding should be preferred to ensure safety; 1. Use DB::select() to execute SELECT queries with parameter binding to prevent SQL injection; 2. Use DB::update() to perform UPDATE operations and return the number of rows affected; 3. Use DB::insert() to insert data; 4. Use DB::delete() to delete data; 5. Use DB::statement() to execute SQL statements without result sets such as CREATE, ALTER, etc.; 6. It is recommended to use whereRaw, selectRaw and other methods in QueryBuilder to combine native expressions to improve security

Python's ternary operator is used to concisely implement if-else judgment, and its syntax is "value_if_trueif conditionelsevalue_if_false"; 1. It can be used for simple assignment, such as returning the corresponding string based on positive and negative values; 2. It can avoid division errors, such as determining that the denominator is non-zero and then division; 3. It can select content according to conditions in string format; 4. It can assign labels to different elements in list derivation formula; it should be noted that this operator is only suitable for binary branches and should not be nested multiple layers. Complex logic should use the traditional if-elif-else structure to ensure readability.

Responsive programming implements high concurrency, low latency non-blocking services in Java through ProjectReactor and SpringWebFlux. 1. ProjectReactor provides two core types: Mono and Flux, supports declarative processing of asynchronous data flows, and converts, filters and other operations through operator chains; 2. SpringWebFlux is built on Reactor, supports two programming models: annotation and functional. It runs on non-blocking servers such as Netty, and can efficiently handle a large number of concurrent connections; 3. Using WebFlux Reactor can improve the concurrency capability and resource utilization in I/O-intensive scenarios, and naturally supports SSE and WebSo.

table-layout:fixed will force the table column width to be determined by the cell width of the first row to avoid the content affecting the layout. 1. Set table-layout:fixed and specify the table width; 2. Set the specific column width ratio for the first row th/td; 3. Use white-space:nowrap, overflow:hidden and text-overflow:ellipsis to control text overflow; 4. Applicable to background management, data reports and other scenarios that require stable layout and high-performance rendering, which can effectively prevent layout jitter and improve rendering efficiency.

Use regular expression capture group in Notepad to effectively reorganize text. First, you need to open the replacement dialog box (Ctrl H), select "Search Mode" as "regular expression", 1. Use () to define the capture group, such as (\w ) to capture words; 2. Use \1 and \2 to reference the corresponding group in the replacement box; 3. Example: Exchange the name "JohnDoe" as "Doe, John", find (\w )\s (\w ), replace it with \2,\1; 4. Date format conversion 2023-12-25 to 25/12/2023, find (\d{4})-(\d{2})-(\d{2}), replace it with \3/\2/\1; 5. Log reordering can extract time, level, ID and other information