MyBatis-Plus 可以根据fieldname生成SFunction吗

当前使用版本(必填,否则不予处理)

3.5.1

请问怎么样根据fieldname生成SFunction 根据SFunction获取fieldname网上有很多 怎么根据fieldname生成SFunction呢

比如我有一个Person类 里面有name属性 我怎么根据name这个字符串和Person这个class 获取SFunction

Comment From: VampireAchao

很棒的问题

Comment From: shuaizai88

public static SFunction getSFunction(Class<?> entityClass, String fieldName) { if (functionMap.containsKey(entityClass.getName() + fieldName)) { return (SFunction)functionMap.get(entityClass.getName() + fieldName); } else { Field field = getDeclaredField(entityClass, fieldName); if (field == null) { throw ExceptionUtils.mpe("This class %s is not have field %s ", new Object[]{entityClass.getName(), fieldName}); } else { SFunction func = null; MethodHandles.Lookup lookup = MethodHandles.lookup(); MethodType methodType = MethodType.methodType(field.getType(), entityClass); String getFunName = "get" + fieldName.substring(0, 1).toUpperCase() + fieldName.substring(1);

            try {
                CallSite site = LambdaMetafactory.altMetafactory(lookup, "invoke", MethodType.methodType(SFunction.class), methodType, lookup.findVirtual(entityClass, getFunName, MethodType.methodType(field.getType())), methodType, 1);
                func = site.getTarget().invokeExact();
                functionMap.put(entityClass.getName() + field, func);
                return func;
            } catch (Throwable var9) {
                throw ExceptionUtils.mpe("This class %s is not have method %s ", new Object[]{entityClass.getName(), getFunName});
            }
        }
    }
}

参考这里面的改一下把。 完整代码在：https://gitee.com/baomidou/mybatis-plus-advance/blob/master/src/main/java/com/baomidou/mybatisplus/advance/injector/FuntionTools.java

Comment From: VampireAchao

见：https://gitee.com/baomidou/mybatis-plus/blob/3.0/mybatis-plus-core/src/test/java/com/baomidou/mybatisplus/test/toolkit/LambdaUtilsTest.java#L49

Comment From: elcnu986

见：https://gitee.com/baomidou/mybatis-plus/blob/3.0/mybatis-plus-core/src/test/java/com/baomidou/mybatisplus/test/toolkit/LambdaUtilsTest.java#L49

`// 通用的检查方法 private void checkEntityExists(Object entityId, String entityName, BaseMapper entityMapper) { try { // 获取实体类类型 Class<?>[] classes = GenericTypeUtils.resolveTypeArguments(entityMapper.getClass(), BaseMapper.class); Class entityClass = (Class) classes[0]; // 通过反射获取实体类的 getId 方法 Method getIdMethod = entityClass.getMethod("getId");

        // 使用lambdaQuery查询记录是否存在
        boolean exists = entityMapper.exists(Wrappers.<T>lambdaQuery()
            .eq(new SFunction<T, Long>() {
                @Override
                public Long apply(T t) {
                    try {
                        return (Long) getIdMethod.invoke(t);
                    } catch (IllegalAccessException e) {
                        throw new RuntimeException(e);
                    } catch (InvocationTargetException e) {
                        throw new RuntimeException(e);
                    }
                }
            }, entityId)
        );
        if (!exists) {
            throw new RuntimeException("错误的id");
        }
    } catch (Exception e) {
        throw new RuntimeException(e);
    }
}`

这是报错信息： Error evaluating expression 'ew.sqlSegment != null and ew.sqlSegment != '''. Cause: org.apache.ibatis.ognl.OgnlException: sqlSegment [com.baomidou.mybatisplus.core.exceptions.MybatisPlusException: java.io.NotSerializableException: org.example.test.MyTest]