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背景

近期在客户的项目中发现在自定义报表样式的时候，存在渲染为html正常，但是在生成pdf的时候，缺少样式的情况。

分析

涉及到的odoo源码中的ir_actions_report.py文件中的代码

    def _prepare_html(self, html):
        '''Divide and recreate the header/footer html by merging all found in html.
        The bodies are extracted and added to a list. Then, extract the specific_paperformat_args.
        The idea is to put all headers/footers together. Then, we will use a javascript trick
        (see minimal_layout template) to set the right header/footer during the processing of wkhtmltopdf.
        This allows the computation of multiple reports in a single call to wkhtmltopdf.

        :param html: The html rendered by render_qweb_html.
        :type: bodies: list of string representing each one a html body.
        :type header: string representing the html header.
        :type footer: string representing the html footer.
        :type specific_paperformat_args: dictionary of prioritized paperformat values.
        :return: bodies, header, footer, specific_paperformat_args
        '''
        IrConfig = self.env['ir.config_parameter'].sudo()
        base_url = IrConfig.get_param('report.url') or IrConfig.get_param('web.base.url')

        # Return empty dictionary if 'web.minimal_layout' not found.
        layout = self.env.ref('web.minimal_layout', False)
        if not layout:
            return {}
        layout = self.env['ir.ui.view'].browse(self.env['ir.ui.view'].get_view_id('web.minimal_layout'))

        root = lxml.html.fromstring(html)
        match_klass = "//div[contains(concat(' ', normalize-space(@class), ' '), ' {} ')]"

        header_node = etree.Element('div', id='minimal_layout_report_headers')
        footer_node = etree.Element('div', id='minimal_layout_report_footers')
        bodies = []
        res_ids = []

        body_parent = root.xpath('//main')[0]
        # Retrieve headers
        for node in root.xpath(match_klass.format('header')):
            body_parent = node.getparent()
            node.getparent().remove(node)
            header_node.append(node)

        # Retrieve footers
        for node in root.xpath(match_klass.format('footer')):
            body_parent = node.getparent()
            node.getparent().remove(node)
            footer_node.append(node)

        # Retrieve bodies
        for node in root.xpath(match_klass.format('article')):
            layout_with_lang = layout
            # set context language to body language
            if node.get('data-oe-lang'):
                layout_with_lang = layout_with_lang.with_context(lang=node.get('data-oe-lang'))
            body = layout_with_lang._render(dict(subst=False, body=lxml.html.tostring(node), base_url=base_url))
            bodies.append(body)
            if node.get('data-oe-model') == self.model:
                res_ids.append(int(node.get('data-oe-id', 0)))
            else:
                res_ids.append(None)

        if not bodies:
            body = bytearray().join([lxml.html.tostring(c) for c in body_parent.getchildren()])
            bodies.append(body)

        # Get paperformat arguments set in the root html tag. They are prioritized over
        # paperformat-record arguments.
        specific_paperformat_args = {}
        for attribute in root.items():
            if attribute[0].startswith('data-report-'):
                specific_paperformat_args[attribute[0]] = attribute[1]

        header = layout._render(dict(subst=True, body=lxml.html.tostring(header_node), base_url=base_url))
        footer = layout._render(dict(subst=True, body=lxml.html.tostring(footer_node), base_url=base_url))

        return bodies, res_ids, header, footer, specific_paperformat_args

1. 我们可以看到在base_url = IrConfig.get_param('report.url') or IrConfig.get_param('web.base.url')中取了系统参数中的report.url或web.base.url中的地址。
2. 在body = layout_with_lang._render(dict(subst=False, body=lxml.html.tostring(node), base_url=base_url))中渲染了我们必要的样式，若这里的url出错，那么这里我们将缺少样式内容。当然，若是全部都通过html原生去实现样式，那么也是可以避免如上的问题。

解决方案

在系统参数添加report.url或者web.base.url的值为http://127.0.0.1:8069（填写本机的地址）