Code Generators – Databases in The Code Generator – Database section

This is the 8th day of my participation in the November Gwen Challenge. Check out the event details: The last Gwen Challenge 2021

Following on from the previous article, “A Study of code automatic generators in The Rule – table Query”, we continue to study the code generation logic in the rule system.

Sql queries that import tables

Click on “Code Generation” in the menu bar and click on the “Import” button in the right pane. In the code Automatic Generator research – Table Query section of The article, we have gone all the way to query the database information_schema.tables to query all the tables in the database.

Our next step is, “Check the my_user table and click OK.” Schematic diagram of operation path and view interface request through F12 debugging, as shown in the figure below.

The requested interface is/tool/gen/importTable, we by the idea of retrieving backend interface, found its ruoyi – generator/com. Ruoyi. The generator/controller/GenController, the diagram below:

The source code of the Controller is as follows :(we supplement the acquisition data of each value through debugging)

/** * import table structure (save) */
    @PreAuthorize("@ss.hasPermi('tool:gen:import')")
    @log (title = "code generation ", businessType = businessType.IMPORT)
    @PostMapping("/importTable")
    public AjaxResult importTableSave(String tables)
    {
        // Through debugging, the format of string tables is: "my_user,table_name_1,table_name_2...."
        String[] tableNames = Convert.toStrArray(tables);
        // tableNames: ["my_user", "table_name_1", "table_name_2"]
        // Query table information
        List<GenTable> tableList = genTableService.selectDbTableListByNames(tableNames);
        / / below
        genTableService.importGenTable(tableList);
        return AjaxResult.success();
    }
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Let’s look at the SQL that queries the table. By searching in XML, it executes SQL as follows:

SELECT
	table_name,
	table_comment,
	create_time,
	update_time
FROM
	information_schema. TABLES
WHERE
	table_name NOT LIKE 'qrtz_%'
AND table_name NOT LIKE 'gen_%'
AND table_schema = (SELECT DATABASE())
AND table_name IN ('my_user')
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Use this query to retrieve the basic information for the my_user table.

So genTableService. ImportGenTable (tableList); What does this sentence do? Let’s keep going.

Import table import

By locating importGenTable, we query its execution method, and we add the parameter values during debugging

/** * import table structure **@paramTableList List of imported tables */
    @Override
    @Transactional
    public void importGenTable(List<GenTable> tableList)
    {
        TableList: [{my_user information}]
        // admin
        String operName = SecurityUtils.getUsername();
        try
        {
            for (GenTable table : tableList)
            {
                String tableName = table.getTableName(); // tableName: my_user
                GenUtils.initTable(table, operName);
                int row = genTableMapper.insertGenTable(table);
                if (row > 0)
                {
                    // Save column information
                    List<GenTableColumn> genTableColumns = genTableColumnMapper.selectDbTableColumnsByName(tableName);
                    for(GenTableColumn column : genTableColumns) { GenUtils.initColumnField(column, table); genTableColumnMapper.insertGenTableColumn(column); }}}}catch (Exception e)
        {
            throw new ServiceException("Import failed:"+ e.getMessage()); }}Copy the code

There is a key data structure: GenTable, which is located in the Domain and corresponds to the table gen_table in the database. The field screenshot is as follows:

Similarly, another table gen_table_column and its corresponding domain class is GenTableColumn, which saves the column information of the generated database table. Its field structure is shown in the following screenshot: The table is associated with a row in the table Gen_table through the field table_id.

What SQL is used to query the columns of a database table?

Upon checking, THE SQL retrieved from the XML is:

SELECT
	column_name,
	(
		CASE
		WHEN (
			is_nullable = 'no' && column_key ! = 'PRI'
		) THEN
			'1'
		ELSE
			NULL
		END
	) AS is_required,
	(
		CASE
		WHEN column_key = 'PRI' THEN
			'1'
		ELSE
			'0'
		END
	) AS is_pk,
	ordinal_position AS sort,
	column_comment,
	(
		CASE
		WHEN extra = 'auto_increment' THEN
			'1'
		ELSE
			'0'
		END
	) AS is_increment,
	column_type
FROM
	information_schema. COLUMNS
WHERE
	table_schema = (SELECT DATABASE())
AND table_name = 'my_user'
	ORDER BY
		ordinal_position
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Query all COLUMNS of the specified table my_user by querying information_schema. COLUMNS and constrainting table_name and the database.

conclusion

Through the import operation, my_user is converted to a few rows of data in gen_table and gen_table_column for subsequent code generation.