Spring_boot使用Example对象做条件查询

30 May, 2023

基本使用方法

 @GetMapping("/subwayLines")
    public ResponseListBase<SubwayLine> list(@RequestParam(required = false, defaultValue = "0") int page,
                                             @RequestParam(required = false, defaultValue = "20") int size,
                                             @RequestParam(required = false, defaultValue = "") String lineNo,
                                             @RequestParam(required = false, defaultValue = "") String lineName) {

        SubwayLine subwayLine = new SubwayLine();

        ExampleMatcher em = ExampleMatcher.matching();

        if(lineNo != null && !lineNo.equals("")) {
            subwayLine.setLineNo(lineNo);
            em = em.withMatcher("lineNo", GenericPropertyMatcher::startsWith);
        }
        if(lineName != null && !lineName.equals("")) {
            subwayLine.setLineName(lineName);
            em = em.withMatcher("lineName", GenericPropertyMatcher::startsWith);
        }
        Page<SubwayLine> subwayLinePage = repository.findAll(Example.of(subwayLine, em), PageRequest.of(page, size));

        return new ResponseListBase<>(subwayLinePage);
    }

注意事项：官方用例写法：
ExampleMatcher matcher = ExampleMatcher.matching()
.withMatcher("firstname", match -> match.endsWith())
.withMatcher("firstname", match -> match.startsWith());
自己的写法：
ExampleMatcher em = ExampleMatcher.matching();
em = exampleMatcher.withMatcher("lineNo", ExampleMatcher.GenericPropertyMatcher::startsWith);
其中重新付值是必须的，查看withMatcher代码会发现，返回一个新的对象，如果不做赋值，会导致没有配置模糊查询

第二个注意点是其中的lineNo必须和对象的名称一致，如果 line_no导致模糊查询不生效。