利用递归遍历获取Java复杂对象（对象的属性仍是对象//list/map）中指定属性的值（一）

冷不防 2022-04-17 03:16 1690阅读 0赞

本示例中又三个对象嵌套：

UserBO：复杂对象，其中一个属性是List<AddressBO>或者Map<AddressBO>

AddressBO：其中一个属性是SubAddressBO

SubAddressBO：包含目标属性addrId，且是string类型，查找addrId的值

任务：UserBO是一个复杂对象，该对象中肯定存在目标属性addrId（String类型,递归方法只能找string类型的属性，找其他类型自行修改代码），只是不知道addrId在哪个子属性中，如果UserBO存在多个addrId属性，那么只遍历出遇到的第一个addrId的值即可。

**注意：（本例子在遍历复杂对象时，如果找到第一个目标属性，则退出，不在继续遍历，后面bolg有遍历复杂对象所有属性的文章）**

**     1、本示例提供了两种方法来获取复杂对象中指定属性的值，一种是利用递归，另一种是直接把复杂对象转换成json串，再截取。**

**    2、本示例对于复杂对象中不包含目标属性时，会返回空字符串。**

**    3、目标属性可以存在于自定义类、list、map、数组中**

**    4、****复杂对象可以是复杂嵌套的BO/List<BO>/Map<Object,BO>,目标属性存在于BO中**

**    5、对于复杂对象是这种嵌套格式(****List<List<BO>>****/****List<Map<Object,BO>>/****Map<Object,List<BO>>****)的没有做测试**

**现在任务交代清楚了，开始贴代码**

### **1、三个Bo类代码** ###

>     import java.io.Serializable;
>     import java.util.List;
>     import java.util.Map;
>     
>     public class UserBO implements Serializable {
>     
>     	private static final long serialVersionUID = 1L;
>     
>     	private String id;
>     	
>     	private String userName;
>     	
>     	private int age;
>     	
>     	private AddressBO address;
>     
>     	private List<AddressBO> list;
>     
>     	private Map<String,AddressBO> map;
>     //	private Date date;
>     //
>     //	public Date getDate() {
>     //		return date;
>     //	}
>     //
>     //	public void setDate(Date date) {
>     //		this.date = date;
>     //	}
>     
>     	private byte b;
>     	private short s;
>     	private boolean bool;
>     	private double dble;
>     	private Byte bb;
>     	private Short ss;
>     	private Integer integer;
>     	private Long aLong;
>     	private Double dd;
>     	private Boolean aBoolean;
>     	private AddressBO[] addressArr;
>     
>     	public UserBO() {
>     	}
>     
>     	public UserBO(String id, String userName, int age, AddressBO address) {
>     		super();
>     		this.id = id;
>     		this.userName = userName;
>     		this.age = age;
>     		this.address = address;
>     	}
>     
>     	public String getId() {
>     		return id;
>     	}
>     
>     	public void setId(String id) {
>     		this.id = id;
>     	}
>     
>     	public String getUserName() {
>     		return userName;
>     	}
>     
>     	public void setUserName(String userName) {
>     		this.userName = userName;
>     	}
>     
>     	public int getAge() {
>     		return age;
>     	}
>     
>     	public void setAge(int age) {
>     		this.age = age;
>     	}
>     	
>     	public AddressBO getAddress() {
>     		return address;
>     	}
>     
>     	public void setAddress(AddressBO address) {
>     		this.address = address;
>     	}
>     
>     	public List<AddressBO> getList() {
>     		return list;
>     	}
>     
>     	public void setList(List<AddressBO> list) {
>     		this.list = list;
>     	}
>     
>     	public Map<String, AddressBO> getMap() {
>     		return map;
>     	}
>     
>     	public void setMap(Map<String, AddressBO> map) {
>     		this.map = map;
>     	}
>     
>     	public byte getB() {
>     		return b;
>     	}
>     
>     	public void setB(byte b) {
>     		this.b = b;
>     	}
>     
>     	public short getS() {
>     		return s;
>     	}
>     
>     	public void setS(short s) {
>     		this.s = s;
>     	}
>     
>     	public boolean isBool() {
>     		return bool;
>     	}
>     
>     	public void setBool(boolean bool) {
>     		this.bool = bool;
>     	}
>     
>     	public double getDble() {
>     		return dble;
>     	}
>     
>     	public void setDble(double dble) {
>     		this.dble = dble;
>     	}
>     
>     	public Byte getBb() {
>     		return bb;
>     	}
>     
>     	public void setBb(Byte bb) {
>     		this.bb = bb;
>     	}
>     
>     	public Short getSs() {
>     		return ss;
>     	}
>     
>     	public void setSs(Short ss) {
>     		this.ss = ss;
>     	}
>     
>     	public Integer getInteger() {
>     		return integer;
>     	}
>     
>     	public void setInteger(Integer integer) {
>     		this.integer = integer;
>     	}
>     
>     	public Long getaLong() {
>     		return aLong;
>     	}
>     
>     	public void setaLong(Long aLong) {
>     		this.aLong = aLong;
>     	}
>     
>     	public Double getDd() {
>     		return dd;
>     	}
>     
>     	public void setDd(Double dd) {
>     		this.dd = dd;
>     	}
>     
>     	public Boolean getaBoolean() {
>     		return aBoolean;
>     	}
>     
>     	public void setaBoolean(Boolean aBoolean) {
>     		this.aBoolean = aBoolean;
>     	}
>     
>     //	@Override
>     //	public String toString() {
>     //		return "UserVo [id=" + id + ", userName=" + userName + ", age=" + age + ", address=[addrId=" + address.getAddrId() + ",addrName=" + address.getAddrName() + "] ]";
>     //	}
>     
>     
>     	public AddressBO[] getAddressArr() {
>     		return addressArr;
>     	}
>     
>     	public void setAddressArr(AddressBO[] addressArr) {
>     		this.addressArr = addressArr;
>     	}
>     }

>     import java.io.Serializable;
>     
>     public class AddressBO implements Serializable {
>     
>     	private static final long serialVersionUID = 1L;
>     
>     //	private String addrId;
>     	
>     	private String addrName;
>     
>     	private SubAddressBO subAddressBO;
>     
>     	public AddressBO() {
>     	}
>     
>     //	public AddressBO(String addrId, String addrName) {
>     //		super();
>     //		this.addrId = addrId;
>     //		this.addrName = addrName;
>     //	}
>     //
>     //	public String getAddrId() {
>     //		return addrId;
>     //	}
>     //
>     //	public void setAddrId(String addrId) {
>     //		this.addrId = addrId;
>     //	}
>     
>     	public String getAddrName() {
>     		return addrName;
>     	}
>     
>     	public void setAddrName(String addrName) {
>     		this.addrName = addrName;
>     	}
>     
>     	public SubAddressBO getSubAddressBO() {
>     		return subAddressBO;
>     	}
>     
>     	public void setSubAddressBO(SubAddressBO subAddressBO) {
>     		this.subAddressBO = subAddressBO;
>     	}
>     }
> 
>

>     import java.io.Serializable;
>     
>     /**
>      * @author: lsl
>      * @date: 2018/11/12
>      */
>     public class SubAddressBO implements Serializable {
>         private String addrId;
>         private int len;
>     
>         public SubAddressBO() {
>         }
>     
>         public SubAddressBO(String addrId, int len) {
>             this.addrId = addrId;
>             this.len = len;
>         }
>     
>         public String getAddrId() {
>             return addrId;
>         }
>     
>         public void setAddrId(String addrId) {
>             this.addrId = addrId;
>         }
>     
>         public int getLen() {
>             return len;
>         }
>     
>         public void setLen(int len) {
>             this.len = len;
>         }
>     }
> 
>

###  **2、递归遍历获取复杂对象的指定属性的值** ###

>     import com.alibaba.fastjson.JSON;
>     import org.apache.commons.lang3.StringUtils;
>     
>     import java.beans.PropertyDescriptor;
>     import java.lang.reflect.Field;
>     import java.lang.reflect.Method;
>     import java.util.*;
>     
>     /**
>      * @author: lsl
>      * @date: 2018/11/9
>      */
>     public class RecursionObject {
>     
>         public static void main(String[] args){
>             //制造数据
>             SubAddressBO subAddressBO0 = new SubAddressBO("subaddress0",10);
>             SubAddressBO subAddressBO1 = new SubAddressBO("subaddress1",20);
>             SubAddressBO subAddressBO2 = new SubAddressBO("subaddress2",30);
>             SubAddressBO subAddressBO3 = new SubAddressBO("subaddress3",40);
>             SubAddressBO subAddressBO4 = new SubAddressBO("subaddress4",50);
>             AddressBO address0 = new AddressBO();
>             address0.setSubAddressBO(subAddressBO0);
>     
>             AddressBO address1 = new AddressBO();
>             address1.setSubAddressBO(subAddressBO1);
>     
>             AddressBO address2 = new AddressBO();
>             address2.setSubAddressBO(subAddressBO2);
>     
>             AddressBO address3 = new AddressBO();
>             address3.setSubAddressBO(subAddressBO3);
>     
>             AddressBO address4 = new AddressBO();
>             address4.setSubAddressBO(subAddressBO4);
>     
>             UserBO userBO = new UserBO();
>     
>             HashMap<String,AddressBO> map = new HashMap<>();
>             map.put("addr1",address1);
>             map.put("addr2",address2);
>     
>             ArrayList<AddressBO> list = new ArrayList<>();
>             list.add(address3);
>             list.add(address4);
>     
>             TestBO testBO = new TestBO();
>             testBO.setAaa("123");
>             testBO.setBbb("456");
>             userBO.setTestBO(testBO);
>             TestVO testVO = new TestVO();
>             testVO.setCcc("ccc11");
>             testVO.setDdd("ddd22");
>             userBO.setTestVO(testVO);
>     
>             List<TestBO> listTestBo = new ArrayList<>();
>             listTestBo.add(testBO);
>             userBO.setListTestBo(listTestBo);
>     
>             userBO.setId("u123");
>             userBO.setUserName("lsl");
>             userBO.setAge(22);
>             //测试目标属性存在于对象属性是自定义类中
>             userBO.setAddress(address0);
>             //测试目标属性存在于对象属性是list的元素中
>             userBO.setList(list);
>             //测试目标属性存在于对象属性是list的元素中
>     //        userBO.setMap(map);
>             //测试目标属性存在于对象属性的数组中
>     //		AddressBO[] arr = new AddressBO[]{address0,address1};
>     //		userBO.setAddressArr(arr);
>     
>             List<UserBO> userBOList = new ArrayList<>();
>             userBOList.add(userBO);
>     
>             //利用方法一
>             Map<String,Object> resultMap = recursionLoopThroughObj(userBO,"addrId");
>             System.err.println("result:" + resultMap.get("proValue"));
>     
>             //利用方法二
>     //        String businessNoFromArg = getBusinessNoFromArg(userBO, "addrId");
>     //        System.err.println("businessNoFromArg=" + businessNoFromArg);
>     
>         }
>     
>         /**
>          * 方法一：利用递归遍历
>          * 用途：从复杂对象中递归遍历，获取string类型的目标属性名的值
>          * 适用条件：该复杂对象中如果存在多个目标属性targetProName，遍历到第一个atargetProName则退出遍历
>          *           targetProName属性必须是string
>          *           targetProName可以存在自定义对象中、list、map、数组中
>          *           如果复杂对象不包含目标属性则返回空字符串
>          *           复杂对象可以是复杂嵌套的BO/List<BO>/Map<Object,BO>,目标属性存在于BO中
>          *           对于复杂对象是list或map嵌套的不做支持。比如List<List<BO></BO>> /List<Map<object,BO>> / Map<object,List<BO>>
>          * @param object 复杂对象
>          * @param targetProName  目标属性名
>          * @return
>          */
>         public static  Map<String,Object> recursionLoopThroughObj(Object object,String targetProName){
>             Map<String,Object> resultMap = new HashMap<>();
>             Class clazz = null;
>             String proValue = "";
>             boolean loopFlag = true;
>             resultMap.put("loopFlag",loopFlag);
>             resultMap.put("proValue",proValue);
>             try {
>                 if (object==null || checkObjectIsSysType(object)){
>                     //如果object是null/基本数据类型/包装类/日期类型，则不需要在递归调用
>                     resultMap.put("loopFlag",false);
>                     resultMap.put("proValue","");
>                     return resultMap;
>                 }
>                 if (object instanceof Map){
>                     Map map = (Map)object;
>                     Map<String,Object> objMap = new HashMap<>();
>                     if (map!=null && map.size()>0){
>                         Iterator iterator = map.values().iterator();
>                         while (iterator.hasNext()){
>                             objMap = recursionLoopThroughObj(iterator.next(),targetProName);
>                             if (!(boolean)objMap.get("loopFlag")){
>                                 return objMap;
>                             }
>                         }
>                     }
>                 }
>     
>                 clazz = object.getClass();
>                 Field[] fields = clazz.getDeclaredFields();
>                 for (Field field : fields) {
>                     String proType = field.getGenericType().toString();
>                     String proName = field.getName();
>                     System.err.println("proName:" + proName + ",proType:" + proType );
>                     if ("class java.lang.String".equals(proType) && targetProName.equals(proName)){
>                         field.setAccessible(true);
>                         proValue = (String)field.get(object);
>                         resultMap.put("loopFlag",false);
>                         resultMap.put("proValue",proValue);
>                         return resultMap;
>                     }else if ("byte".equals(proType) || "short".equals(proType) || "int".equals(proType)|| "long".equals(proType)|| "double".equals(proType) || "float".equals(proType) || "boolean".equals(proType) ){
>                         //属性是基本类型跳过
>                         continue;
>                     }else if ("class java.lang.Byte".equals(proType) || "class java.lang.Short".equals(proType) || "class java.lang.Integer".equals(proType) || "class java.lang.Long".equals(proType) || "class java.lang.Double".equals(proType) || "class java.lang.Float".equals(proType) || "class java.lang.Boolean".equals(proType) || ("class java.lang.String".equals(proType) && !targetProName.equals(proName))){
>                         //属性是包装类跳过
>                         continue;
>                     }else if (proType.startsWith("java.util")){
>                         //属性是集合类型则遍历
>                         if (proType.startsWith("java.util.List")){
>                             //对List类型的属性遍历
>                             PropertyDescriptor descriptor = new PropertyDescriptor(field.getName(), clazz);
>                             Method method = descriptor.getReadMethod();
>                             List list = (List)method.invoke(object);
>                             Map<String,Object> objMap = new HashMap<>();
>                             if (list!=null && list.size()>0){
>                                 int len = list.size();
>                                 for (int i= 0;i<len;i++){
>                                     objMap = recursionLoopThroughObj(list.get(i),targetProName);
>                                     if (!(boolean)objMap.get("loopFlag")){
>                                         return objMap;
>                                     }
>                                 }
>                             }
>     
>                         }else if (proType.startsWith("java.util.Map")){
>                             //对Map类型的属性遍历
>                             PropertyDescriptor descriptor = new PropertyDescriptor(field.getName(), clazz);
>                             Method method = descriptor.getReadMethod();
>                             Map map = (Map)method.invoke(object);
>                             Map<String,Object> objMap = new HashMap<>();
>                             if (map!=null && map.size()>0){
>                                 for (Object obj : map.values()){
>                                     objMap = recursionLoopThroughObj(obj,targetProName);
>                                     if (!(boolean)objMap.get("loopFlag")){
>                                         return objMap;
>                                     }
>                                 }
>                             }
>     
>                         }
>     
>                     }else if(field.getType().isArray()){
>                         //属性是数组类型则遍历
>                         field.setAccessible(true);
>                         Object[] objArr = (Object[]) field.get(object);
>                         Map<String,Object> objMap = new HashMap<>();
>                         if (objArr!=null && objArr.length>0){
>                             for (Object arr : objArr){
>                                 objMap = recursionLoopThroughObj(arr,targetProName);
>                                 if (!(boolean)objMap.get("loopFlag")){
>                                     return objMap;
>                                 }
>                             }
>                         }
>     
>                     }else  {
>                         //class类型的遍历
>                         PropertyDescriptor descriptor = new PropertyDescriptor(field.getName(), clazz);
>                         Method method = descriptor.getReadMethod();
>                         Object obj = method.invoke(object);
>                         Map<String,Object> objMap = new HashMap<>();
>                         if (obj!= null){
>                             objMap = recursionLoopThroughObj(obj,targetProName);
>                             if (!(boolean)objMap.get("loopFlag")){
>                                 return objMap;
>                             }
>                         }else {
>                             continue;
>                         }
>     
>                     }
>                 }
>             } catch (Exception e) {
>                 System.err.println("err:" + e);
>             }
>             return resultMap;
>         }
>     
>         /**
>          * 检查object是否为java的基本数据类型/包装类/java.util.Date/java.sql.Date
>          * @param object
>          * @return
>          */
>         public static boolean checkObjectIsSysType(Object object){
>             String objType = object.getClass().toString();
>             if ("byte".equals(objType) || "short".equals(objType) || "int".equals(objType)|| "long".equals(objType)|| "double".equals(objType) || "float".equals(objType) || "boolean".equals(objType)){
>                 return true;
>             }else if ("class java.lang.Byte".equals(objType) || "class java.lang.Short".equals(objType) || "class java.lang.Integer".equals(objType) || "class java.lang.Long".equals(objType) || "class java.lang.Double".equals(objType) || "class java.lang.Float".equals(objType) || "class java.lang.Boolean".equals(objType) || "class java.lang.String".equals(objType)){
>                 return true;
>             }else {
>                 return  false;
>             }
>     
>         }
>     
>         /**
>          * 方法二：从复杂对象中获取string类型的目标属性targetProName的值
>          * 把对象转换成json字符串，然后截取第一次出现的targetProName的值
>          * 适用条件：同方法一
>          * @param object 复杂对象
>          * @param targetProName 目标属性
>          * @return
>          */
>         public static String getBusinessNoFromArg(Object object,String targetProName){
>             String jsonString = JSON.toJSONString(object);
>             System.err.println("jsonString=" + jsonString);
>             jsonString = StringUtils.substringAfter(jsonString,"\""+targetProName + "\":\"");
>             jsonString = StringUtils.substringBefore(jsonString,"\"");
>             return jsonString;
>         }
>     }

### **3、addrId存在于map中运行结果图：** ###

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2Roa2xzbA_size_16_color_FFFFFF_t_70][]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2Roa2xzbA_size_16_color_FFFFFF_t_70]: /images/20220417/d5ab89d325784d6fb474d10e6d7b253f.png