java 动态 Lambda
Posted 正怒月神
tags:
篇首语：本文由小常识网(cha138.com)小编为大家整理，主要介绍了java 动态 Lambda相关的知识，希望对你有一定的参考价值。
https://blog.csdn.net/hanjun0612/article/details/121972663?spm=1001.2014.3001.5501一，反射类
package com.leadtrans.report.common;
import org.springframework.aop.support.AopUtils;
import org.springframework.context.ApplicationContext;
import org.springframework.core.DefaultParameterNameDiscoverer;
import org.springframework.stereotype.Service;
import javax.annotation.Resource;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.math.BigDecimal;
import java.util.*;
import java.util.function.Supplier;
import java.util.stream.Collectors;
import java.util.stream.Stream;
/**
* @author: Tyler
* @createDate: 2021/12/9
*/
public class ReflectionUtil
/**
* 调用示例
* public ApiResponse<String> test() throws Exception
* Class[] argsType=new Class[]Class.forName("java.lang.String");
* Object[] args=new Object[]"hello";
* ReflectionUtil.invokeMethod(new ReportImpl(),"Test",argsType,args);
* return new ApiResponse().Success("str");
*
* @param owner 类的实例
* @param methodName 方法名
* @param argsClass 参数类型
* @param args 参数
* @return
* @throws Exception
*/
public static Object invokeMethod(Object owner,String methodName,Class[] argsClass,Object[] args) throws Exception
Object objRtn=null;
Class ownerClass = owner.getClass();
Method method = ownerClass.getMethod(methodName, argsClass);
objRtn = method.invoke(owner, args);
return objRtn;
public static Field getFiled(Object obj,String filedName)
Field field=null;
try
field = obj.getClass().getDeclaredField(filedName);
field.setAccessible(true);
catch (NoSuchFieldException e)
e.printStackTrace();
finally
return field;
public static Object getFiledValue(Object obj,String filedName)
Object objValue=null;
try
Field field = getFiled(obj,filedName);
objValue = field.get(obj);
catch (IllegalAccessException e)
e.printStackTrace();
finally
return objValue;
二，动态lambda
Filter
/**
* Lambda 动态 Filter
*
* @param list 数据
* @param equalsMap contains 过滤器
* @param notEqualsMap !contains 过滤器
* @param <T>
* @return
*/
public <T> List<T> getDataListFilter(List<T> list, Map<String, List<Object>> equalsMap, Map<String, List<Object>> notEqualsMap, Map<String, Integer> dateLessMap)
Supplier<Stream<T>> st = () -> list.stream();
if (equalsMap != null)
for (Map.Entry<String, List<Object>> item : equalsMap.entrySet())
Supplier<Stream<T>> stFilter = st;
st = () -> stFilter.get()
.filter(x -> item.getValue().contains(
ReflectionUtil.getFiledValue(x, item.getKey()) == null
? "null"
: ReflectionUtil.getFiledValue(x, item.getKey()))
);
if (notEqualsMap != null)
for (Map.Entry<String, List<Object>> item : notEqualsMap.entrySet())
Supplier<Stream<T>> stFilter = st;
st = () -> stFilter.get()
.filter(x -> !item.getValue().contains(
ReflectionUtil.getFiledValue(x, item.getKey()) == null
? "null"
: ReflectionUtil.getFiledValue(x, item.getKey()))
);
if (dateLessMap != null)
for (Map.Entry<String, Integer> item : dateLessMap.entrySet())
Supplier<Stream<T>> stFilter = st;
st = () -> stFilter.get()
.filter(x ->
Object colVal = ReflectionUtil.getFiledValue(x, item.getKey());
if (colVal != null && StringUtils.isNotBlank(colVal.toString()))
colVal = DateUtil.add(DateUtil.parse2(colVal.toString()), Calendar.DATE, item.getValue());
return new Date().after((Date)colVal);
return false;
);
List<T> rList = st.get().collect(Collectors.toList());
return rList;
Group
/**
* Lambda 动态 Group
*
* @param list 数据
* @param fieldGroups 聚合字段
* @param <T>
* @return
*/
public <T> Map<String, List<T>> getDataListGroup(List<T> list, List<String> fieldGroups)
Map<String, List<T>> map = list.stream().collect(Collectors.groupingBy(x ->
String groupItem = "";
for (String y : fieldGroups)
groupItem += ReflectionUtil.getFiledValue(x, y) + "_";
return groupItem;
));
return map;
获取数据
/**
* 输出数据
*
* @param dataList 数据源
* @param fieldNames 属性名
* @param calculateNames 需要计算的列
* @return
*/
public <T> List<List<Object>> getDataList(Map<String, List<T>> dataList, List<String> fieldNames, List<String> calculateNames)
List<List<Object>> data = new ArrayList<>();
for (Map.Entry<String, List<T>> entry : dataList.entrySet())
List<Object> obj = new ArrayList<>();
for (String colName : fieldNames)
//普通字段
if (!calculateNames.contains(colName))
//addDate
if (colName.toLowerCase().replace(" ", "").startsWith("addDate(".toLowerCase()))
String addDateName = colName.substring("addDate(".length(), colName.indexOf(")"));
String[] args = addDateName.split(",");
Object colVal = ReflectionUtil.getFiledValue(entry.getValue().get(0), args[1]);
if (colVal != null && StringUtils.isNotBlank(colVal.toString()))
colVal = DateUtil.toDateString(DateUtil.add(DateUtil.parse2(colVal.toString()), Calendar.DATE, Integer.parseInt(args[0])), "yyyy-MM-dd");
obj.add(colVal);
else
//判断属性是否存在
Object col = ReflectionUtil.getFiled(entry.getValue().get(0), colName);
if (col == null)
obj.add(entry.getKey());
else
//属性存在，则取值
Object colVal = ReflectionUtil.getFiledValue(entry.getValue().get(0), colName);
obj.add(colVal);
//计算count 标签
else if (colName.toLowerCase().replace(" ", "").startsWith("count(".toLowerCase()))
String countName = colName.substring("count(".length(), colName.indexOf(")"));
String[] args = countName.split(",");
//如果args>1，说明有条件
if (args.length > 1)
//获取多个条件
String[] argsArr = args[0].split("\\\\|");
Supplier<Stream<T>> st = ()->entry.getValue().stream();
for (String argsSimple : argsArr)
Supplier<Stream<T>> stFilter = st;
//获取单个条件，拼接
String[] argsKV;
if (argsSimple.indexOf("!:") > 0)
//不等
argsKV = argsSimple.split("!:");
st = () ->stFilter.get()
.filter(x -> !(ReflectionUtil.getFiledValue(x, argsKV[0]) == null ? "null" : ReflectionUtil.getFiledValue(x, argsKV[0]).toString()).equals(argsKV[1]));
else
//相等
argsKV = argsSimple.split(":");
st = () -> stFilter.get()
.filter(x -> (ReflectionUtil.getFiledValue(x, argsKV[0]) == null ? "null" : ReflectionUtil.getFiledValue(x, argsKV[0]).toString()).equals(argsKV[1]));
Object colVal = st.get().collect(Collectors.toList()).size();
obj.add(colVal);
else
Object colVal = entry.getValue().size();
obj.add(colVal);
//计算countDistinct标签
else if (colName.toLowerCase().replace(" ", "").startsWith("countDistinct(".toLowerCase()))
String countName = colName.substring("countDistinct(".length(), colName.indexOf(")"));
String[] args = countName.split(",");
//如果args>1，说明有条件
if (args.length > 1)
//获取多个条件
String[] argsArr = args[0].split("\\\\|");
Supplier<Stream<Object>> st = ()-> (Stream<Object>) entry.getValue().stream();
for (String argsSimple : argsArr)
Supplier<Stream<Object>> stFilter = st;
//获取单个条件，拼接
String[] argsKV;
//不等
if (argsSimple.indexOf("!:") > 0)
argsKV = argsSimple.split("!:");
st = () -> stFilter.get()
.filter(x -> !(ReflectionUtil.getFiledValue(x, argsKV[0]) == null ? "null" : ReflectionUtil.getFiledValue(x, argsKV[0]).toString()).equals(argsKV[1]))
.map(x -> ReflectionUtil.getFiledValue(x, args[1]))
.distinct();
else
//相等
argsKV = argsSimple.split(":");
st = () -> stFilter.get()
.filter(x -> (ReflectionUtil.getFiledValue(x, argsKV[0]) == null ? "null" : ReflectionUtil.getFiledValue(x, argsKV[0]).toString()).equals(argsKV[1]))
.map(x -> ReflectionUtil.getFiledValue(x, args[1]))
.distinct();
Object colVal = st.get().collect(Collectors.toList()).size();
obj.add(colVal);
else
Object colVal = entry.getValue().stream()
.map(x -> ReflectionUtil.getFiledValue(x, args[0]))
.distinct()
.collect(Collectors.toList()).size();
obj.add(colVal);
//计算sum 标签
else if (colName.toLowerCase().replace(" ", "").startsWith("sum(".toLowerCase()))
String sumName = colName.substring("sum(".length(), colName.indexOf(")"));
String[] args = sumName.split(",");
//如果args>1，说明有条件
if (args.length > 1)
//获取多个条件
String[] argsArr = args[0].split("\\\\|");
Supplier<Stream<T>> st = ()->entry.getValue().stream();
for (String argsSimple : argsArr)
Supplier<Stream<T>> stFilter = st;
//获取单个条件，拼接
String[] argsKV;
//不等
if (argsSimple.indexOf("!:") > 0)
argsKV = argsSimple.split("!:");
st = () -> stFilter.get()
.filter(x -> !(ReflectionUtil.getFiledValue(x, argsKV[0]) == null ? "null" : ReflectionUtil.getFiledValue(x, argsKV[0]).toString()).equals(argsKV[1]));
else
//相等
argsKV = argsSimple.split(":");
st = () -> stFilter.get()
.filter(x -> (ReflectionUtil.getFiledValue(x, argsKV[0]) == null ? "null" : ReflectionUtil.getFiledValue(x, argsKV[0]).toString()).equals(argsKV[1]));
Object colVal = st.get()
.map(x -> new BigDecimal(ReflectionUtil.getFiledValue(x, args[1]) == null ? "0" : ReflectionUtil.getFiledValue(x, args[1]).toString().replace(",", "")))
.reduce(BigDecimal.ZERO, BigDecimal::add);
obj.add(colVal);
else
Object colVal = entry.getValue().stream()
.map(x -> new BigDecimal(ReflectionUtil.getFiledValue(x, args[0]) == null ? "0" : ReflectionUtil.getFiledValue(x, args[0]).toString()))
.reduce(BigDecimal.ZERO, BigDecimal::add);
obj.add(colVal);
//计算列
else
Object colVal = entry.getValue().stream()
.map(x -> new BigDecimal(ReflectionUtil.getFiledValue(x, colName) == null ? "0" : ReflectionUtil.getFiledValue(x, colName).toString().replace(",", "")))
.reduce(BigDecimal.ZERO, BigDecimal::add);
obj.add(colVal);
//添加到data
data.add(obj);
//默认按照第一列排序
data.sort(comparing(x -> (x.get(0) == null ? "" : x.get(0).toString())));
return data;
总计列
/**
* 添加合计列
*
* @param fieldNames 字段
* @param data 数据
* @param calculateHeadsNames 计算列
* @return
*/
public List<Object> addTotal(List<String> fieldNames, List<List<Object>> data, List<String> calculateHeadsNames)
List<Object> totalLine = new ArrayList<>();
try
//按照数据的长度，初始化大小
if (data.size() > 0)
data.get(0).forEach(x -> totalLine.add(""));
//增加TOTAL字样
totalLine.set(0, "TOTAL");
//计算列
if (calculateHeadsNames != null && calculateHeadsNames.size() > 0)
for (String colName : calculateHeadsNames)
Integer index = fieldNames.indexOf(colName);
if (index > -1)
BigDecimal val = data.stream().map(x -> new BigDecimal(x.get(index) == null ? "0" : x.get(index).toString()))
.reduce(BigDecimal::add).get();
totalLine.set(index, val);
return totalLine;
catch (Exception e)
e.printStackTrace();
finally
return totalLine;
三，测试
@Test
public void testLambda() throws NoSuchFieldException, IllegalAccessException
List<MyTest> list=new ArrayList<>();
list.add(new MyTest(0,"n0","hobby0",1));
list.add(new MyTest(1,"n1","hobby1",1));
list.add(new MyTest(1,"n2","hobby2",1));
list.add(new MyTest(2,"n3","hobby3",1));
list.add(new MyTest(2,"n4","hobby4",1));
list.add(new MyTest(3,"n5","hobby5",1));
list.add(new MyTest(3,"n6","hobby6",1));
list.add(new MyTest(3,"n7","hobby7",1));
list.add(new MyTest(3,"n8","hobby7",1));
String json = FileUtil.readFile(System.getProperty("user.dir") + "/reportArgs"+"/myTest.json");
ReportArgsReq reportArgsReq= JSON.parseObject(json,ReportArgsReq.class);
List<MyTest> rList = report.getDataListFilter(list, reportArgsReq.getEqualsMap(),reportArgsReq.getNotEqualsMap());
Map<String,List<MyTest>> rMap=report.getDataListGroup(rList,reportArgsReq.getFieldGroups());
System.out.println(rMap.size());
// List<FileTypeVO> rList=list.stream().filter(x->x.)
MyTest.java
package com.leadtrans.report.model.DB;
import com.baomidou.mybatisplus.annotation.TableId;
import com.baomidou.mybatisplus.annotation.TableName;
import java.util.Date;
/**
* @author: Tyler
* @createDate: 2021/12/7
*/
@TableName(value = "myTest")
public class MyTest
@TableId
private Integer id;
private String name;
private String hobby;
private Integer amount;
public MyTest()
public MyTest(Integer id,String name,String hobby,Integer amount)
this.id=id;
this.name=name;
this.hobby=hobby;
this.amount=amount;
//get;set;
myTest.json
"equalsMap": ,
"notEqualsMap": ,
"fieldGroups": ["id"],
"headsExcel": ["id","name","hobby","amount sum"],
"fieldNames": ["id","name","hobby","sum(amount)"],
"calculateFieldNames": ["sum(amount)"]
四，进阶
其实还有一些其他的用法。
样例：
"equalsMap": "INCO": ["FOB","EXWORK"],"Test": ["a","b"],
"notEqualsMap": "Test1": ["hello"],"Test2": ["t1","t2"],
"fieldGroups": ["pol","pod","jobName"],
"headsExcel": ["jobName","pol","pod","INCO","TEU","AIR Bill","LCL Bill","jobProfit"],
"fieldNames": ["jobName","pol","pod","INCO","sum(type:SEA,TEU)","count(type:AIR,shipmentID)","count(mode:LCL,shipmentID)","jobProfit"],
"calculateFieldNames": ["sum(type:SEA|mode:FCL,TEU)","count(type:AIR,shipmentID)","count(mode:LCL,shipmentID)","jobProfit"],
"calcRatioHeads": ["TEU","AIR Bill","LCL Bill","jobProfit"],
"groupReportList": ["jobName","pol","pod"]
解释：
| 字段 | 注释 |
|---|---|
| equalsMap | 需要过滤的相等字段。 |
| notEqualsMap | 需要过滤的不等字段。 |
| fieldGroups | 分组字段。 |
| headsExcel | 写入excel的表头 |
| fieldNames | 使用到的字段,对应到表头。 |
| calculateFieldNames | 需要计算的字段,int,decimal,非数值类型（Count）..... （ sum(type:SEA|mode:FCL,TEU) : 计算type为sea，并且mode为FCL 的TEU 总和 count(type:AIR,shipmentID)：计算type为Air，的shipment数量 jobProfit / sum(jobProfit)：同样的含义，直接计算jobProfit的总合 countDistinct(type:AIP,shipmentID)：去重后计算count ） |
以上是关于java 动态 Lambda的主要内容，如果未能解决你的问题，请参考以下文章