设计模式 + java8方法引用 实现任意表的过滤器

会用到下面2个依赖，原因是在今天的案例中，我想在我代码中使用上Entity::getFieldName 这种形式

LambdaQueryWrapper<ApplicationDashboard> queryWrapper = new LambdaQueryWrapper<>();
queryWrapper.eq(ApplicationDashboard::getAppCode, "Code1");// 使用这种形式的编码

之所以喜欢这种形式是因为修改属性字段名称时直接用Idea的重命名修改，这样我们不需要去自己去其他使用到的地方一个个改。
举个例子来说，AppCode 重命名为Code
那么IDEA重命名后，相应的get方法也会自己修改好

queryWrapper.eq(ApplicationDashboard::getCode, "Code1");

用到的依赖

 <dependency><groupId>com.baomidou</groupId><artifactId>mybatis-plus-boot-starter</artifactId><version>3.5.5</version></dependency><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId><version>1.18.30</version><scope>provided</scope></dependency>

场景

我希望生成这样一条查询sql，其中application_dashboard表只是一个例子，需要实现任意表的 sql 查询

select * from application_dashboard 
where 
(app_code='AppCode1' or app_code='AppCode2' ) 
and app_context is like '%dev%' 
and type <> '3'

因为一些原因，我们需要返回下面的filter字符串，大致上和上面的where condition类似

// 生成filter：
((appCode__equ__'AppCode1')||(appCode__equ__'AppCode2')) && appContext__equ__/.*dev.*/ && type__nequ__'3'

用户可以通过UI 表单去动态生成不同的filter。

我的代码实现如下

1、实体

假设是ApplicationDashboard 表，字段如下ApplicationDashboard 的属性字段。

import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;import java.util.Date;@Data
@Builder
@NoArgsConstructor
@AllArgsConstructor
public class ApplicationDashboard {private String appCode;private String appName;private String appContext;private String appId;private String type;private Date updateDate;
}

最终的测试代码

import top.yumbo.entity.ApplicationDashboard;
import top.yumbo.util.CustomFilter;import java.util.Arrays;
import java.util.List;public class CustomFilterDemo {public static void main(String[] args) throws Exception {/*** 翻译：* AppCode为 AppCode1 或 AppCode2* context包含 dev* type 不为 3*/List<CustomFilter> filters = Arrays.asList(CustomFilter.builder().columns(ApplicationDashboard::getAppCode).value("AppCode1,AppCode2").operation(OperationEnum.EQUAL_TO).asList(true).build(),CustomFilter.builder().columns(ApplicationDashboard::getAppContext).value("dev").build(),CustomFilter.builder().columns(ApplicationDashboard::getType).value("3").operation(OperationEnum.EQUAL_TO).invert(true).build());// ((appCode__equ__'AppCode1')||(appCode__equ__'AppCode2'))&&appContext__equ__/.*dev.*/&&type__nequ__'3'System.out.println(CustomFilter.getFilter(filters));}
}

CustomFilter 的实现

import com.baomidou.mybatisplus.core.toolkit.LambdaUtils;
import com.baomidou.mybatisplus.core.toolkit.support.LambdaMeta;
import com.baomidou.mybatisplus.core.toolkit.support.SFunction;
import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;
import org.apache.ibatis.reflection.property.PropertyNamer;
import org.springframework.util.StringUtils;
import top.yumbo.entity.ApplicationDashboard;import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;@Data
@Builder
@AllArgsConstructor
@NoArgsConstructor
public class CustomFilter {private SFunction<ApplicationDashboard, String> columns;private String value;@Builder.Defaultprivate boolean ignore = true;private boolean asList;private boolean invert;// 反@Builder.Defaultprivate OperationEnum operation = OperationEnum.CONTAINS;private String getOperation() {if (invert) {return "__nequ__";} else {return "__equ__";}}private String getVal(String value){return operation.getOperationValue(value);}public String getFilter() {String result = "";if (StringUtils.hasText(value)) {LambdaMeta lambdaMeta = LambdaUtils.extract(columns);String filedName = PropertyNamer.methodToProperty(lambdaMeta.getImplMethodName());if (asList) {List<String> valList = Arrays.asList(value.split(","));List<String> list = valList.stream().map(String::trim).map(val -> "(" + filedName + getOperation() + getVal(val) + ")").collect(Collectors.toList());return "(" + mergeList(list, "||") + ")";} else {return filedName + getOperation() + getVal(value);}}return result;}public static String getFilter(List<CustomFilter> filters) {return getFilter(filters, "&&");}public static String getFilter(List<CustomFilter> filters, String concat) {List<String> filterList = filters.stream().map(CustomFilter::getFilter).collect(Collectors.toList());return mergeList(filterList, concat);}public static String mergeList(List<String> list, String concat) {if (list != null && list.size() > 0) {return list.size() == 1 ? list.get(0) : list.stream().reduce((str1, str2) -> str1 + concat + str2).get();}return "";}
}

OperationEnum

import java.util.function.Function;public enum OperationEnum {EQUAL_TO((value) -> "'" + value + "'"),CONTAINS((value) -> "/.*" + value + ".*/"),START_WITH((value) -> "/" + value + ".*/"),END_WITH((value) -> "/.*" + value + "/");private final Function<String, String> function;OperationEnum(Function<String, String> function) {this.function = function;}public String getOperationValue(String value) {return function.apply(value);}}