如何用java递归生成带children的json串
最新回答
夏晨曦
2025-03-01 03:18:35
灬夏伤
2025-03-01 07:59:36
字符串
的json操作不建议。class Node{
private String id;
private String parentId;
private List<Node> children;
public void addChildren(Node child){
getChildren().add(child);
}
public List<Node> getChildren();
public String transformTojson(Node node ,StringBuffer jsonStr){
//递归
if(jsonStr ==null){
StringBuffer jsonStr=new ();
}
if(node.id!=null){
//拼接父节点json串
jsonStr.append(id:node.id,children:#&children);
}
List childNodeList = node.getChildren();
StringBuffer childrenSB = new();
for( Node node :childNodeList){
childrenSB=transformTojson(node);
}
sonStr.replaceFirst("#&children",childrenSB);
return jsonStr;
}
}
伪代码大概这样。
transformTojson方法可以不自己写，直接使用第三方工具jar包的json转化方法，比如gjson。
真情已被瓦解
2025-03-01 11:35:24
import java.util.Collection;
import java.util.Map;
import org.apache.commons.lang3.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import com.fasterxml.jackson.annotation.JsonInclude.Include;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.JavaType;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationFeature;
import com.fasterxml.jackson.databind.util.JSONPObject;
import com.fasterxml.jackson.module.jaxb.JaxbAnnotationModule;
/**
* 简单封装Jackson，实现JSON String<->Java Object的Mapper.
*
* 封装不同的输出风格, 使用不同的builder函数创建实例.
*
*/
public class JsonMapper {
private static Logger logger = LoggerFactory.getLogger(JsonMapper.class);
private ObjectMapper mapper;
public JsonMapper() {
this(null);
}
public JsonMapper(Include include) {
mapper = new ObjectMapper();
// 设置输出时包含属性的风格
if (include != null) {
mapper.setSerializationInclusion(include);
}
// 设置输入时忽略在JSON字符串中存在但Java对象实际没有的属性
mapper.disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES);
}
public static JsonMapper alwaysMapper() {
return new JsonMapper(Include.ALWAYS);
}
public static JsonMapper nonNullMapper() {
return new JsonMapper(Include.NON_NULL);
}
/**
* 创建只输出非Null且非Empty(如List.isEmpty)的属性到Json字符串的Mapper,建议在外部接口中使用.
*/
public static JsonMapper nonEmptyMapper() {
return new JsonMapper(Include.NON_EMPTY);
}
/**
* 创建只输出初始值被改变的属性到Json字符串的Mapper, 最节约的存储方式，建议在内部接口中使用。
*/
public static JsonMapper nonDefaultMapper() {
return new JsonMapper(Include.NON_DEFAULT);
}
/**
* Object可以是POJO，也可以是Collection或数组。 如果对象为Null, 返回"null". 如果集合为空集合, 返回"[]".
*/
public String toJson(Object object) {
try {
return mapper.writeValueAsString(object);
}
catch (IOException e) {
logger.warn("write to json string error:" + object, e);
return null;
}
}
/**
* 反序列化POJO或简单Collection如List<String>.
*
* 如果JSON字符串为Null或"null"字符串, 返回Null. 如果JSON字符串为"[]", 返回空集合.
*
* 如需反序列化复杂Collection如List<MyBean>, 请使用fromJson(String, JavaType)
*
* @see #fromJson(String, JavaType)
*/
public <T> T fromJson(String jsonString, Class<T> clazz) {
if (StringUtils.isEmpty(jsonString)) {
return null;
}
try {
return mapper.readValue(jsonString, clazz);
}
catch (IOException e) {
logger.warn("parse json string error:" + jsonString, e);
return null;
}
}
/**
* 反序列化复杂Collection如List<Bean>,
* 先使用createCollectionType()或contructMapType()构造类型, 然后调用本函数.
*
* @see #createCollectionType(Class, Class...)
*/
public <T> T fromJson(String jsonString, JavaType javaType) {
if (StringUtils.isEmpty(jsonString)) {
return null;
}
try {
return (T) mapper.readValue(jsonString, javaType);
}
catch (IOException e) {
logger.warn("parse json string error:" + jsonString, e);
return null;
}
}
/**
* 构造Collection类型.
*/
public JavaType contructCollectionType(Class<? extends Collection> collectionClass, Class<?> elementClass) {
return mapper.getTypeFactory().constructCollectionType(collectionClass, elementClass);
}
/**
* 构造Map类型.
*/
public JavaType contructMapType(Class<? extends Map> mapClass, Class<?> keyClass, Class<?> valueClass) {
return mapper.getTypeFactory().constructMapType(mapClass, keyClass, valueClass);
}
/**
* 当JSON里只含有Bean的部分属性时，更新一个已存在Bean，只覆盖该部分的属性.
*/
public void update(String jsonString, Object object) {
try {
mapper.readerForUpdating(object).readValue(jsonString);
}
catch (JsonProcessingException e) {
logger.warn("update json string:" + jsonString + " to object:" + object + " error.", e);
}
catch (IOException e) {
logger.warn("update json string:" + jsonString + " to object:" + object + " error.", e);
}
}
/**
* 输出JSONP格式数据.
*/
public String toJsonP(String functionName, Object object) {
return toJson(new JSONPObject(functionName, object));
}
/**
* 设定是否使用Enum的toString函数来读写Enum, 为False时时使用Enum的name()函数来读写Enum, 默认为False.
* 注意本函数一定要在Mapper创建後, 所有的读写动作之前调用.
*/
public void enableEnumUseToString() {
mapper.enable(SerializationFeature.WRITE_ENUMS_USING_TO_STRING);
mapper.enable(DeserializationFeature.READ_ENUMS_USING_TO_STRING);
}
/**
* 支持使用Jaxb的Annotation，使得POJO上的annotation不用与Jackson耦合。
* 默认会先查找jaxb的annotation，如果找不到再找jackson的。
*/
public void enableJaxbAnnotation() {
JaxbAnnotationModule module = new JaxbAnnotationModule();
mapper.registerModule(module);
}
/**
* 取出Mapper做进一步的设置或使用其他序列化API.
*/
public ObjectMapper getMapper() {
return mapper;
}
}
接住路过的风
2025-03-01 20:59:02
在运行之前需要以下公共类:
commons-beanutils.jar
commons-collections.jar
commons-lang.jar
commons-logging.jar
ezmorph-1.0.6.jar
json-lib-2.3-jdk15.jar
package com.test;
import java.util.ArrayList;
public class TreeNode {
private String id;
private String pid;
private String name;
private String remark;
private ArrayList<TreeNode> children = new ArrayList<TreeNode>();
public TreeNode(String id, String pid, String name, String remark) {
this.id = id;
this.pid = pid;
this.name = name;
this.remark = remark;
}
public void add(TreeNode node) {//递归添加节点
if ("0".equals(node.pid)) {
this.children.add(node);
} else if (node.pid.equals(this.id)) {
this.children.add(node);
} else {
for (TreeNode tmp_node : children) {
tmp_node.add(node);
}
}
}
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getRemark() {
return remark;
}
public void setRemark(String remark) {
this.remark = remark;
}
public ArrayList<TreeNode> getChildren() {
return children;
}
public void setChildren(ArrayList<TreeNode> children) {
this.children = children;
}
}
测试类Test.java
package com.test;
import net.sf.json.JSONArray;
import net.sf.json.JSONObject;
public class Test {
public static void main(String[] args) {
TreeNode root = new TreeNode("0", "0", "000000", "00JJJ");
TreeNode node = null;
node = new TreeNode("1", "0", "111111", "11AAA");
root.add(node);
node = new TreeNode("2", "0", "222222", "11BBB");
root.add(node);
node = new TreeNode("3", "2", "333333", "11CCC");
root.add(node);
// JSONObject obj = JSONObject.fromObject(root);//有根
JSONArray obj = JSONArray.fromObject(root.getChildren());// 不要根
System.out.println(obj.toString());
}
}
笑死大姨妈
2025-03-01 09:13:10
package com.bochy.common.utils;
/*
*
* 转换JSON帮助�??
*
* */
import java.beans.IntrospectionException;
import java.beans.Introspector;
import java.beans.PropertyDescriptor;
import java.util.List;
import java.util.Map;
import java.util.Set;
public class JsonUtils {
public static String stringToJson(String s) {
if (s == null) {
return nullToJson();
}
StringBuilder sb = new StringBuilder();
for (int i = 0; i < s.length(); i++) {
char ch = s.charAt(i);
switch (ch) {
case '"':
sb.append("\\\"");
break;
case '\\':
sb.append("\\\\");
break;
case '\b':
sb.append("\\b");
break;
case '\f':
sb.append("\\f");
break;
case '\n':
sb.append("\\n");
break;
case '\r':
sb.append("\\r");
break;
case '\t':
sb.append("\\t");
break;
case '/':
sb.append("\\/");
break;
default:
if (ch >= '\u0000' && ch <= '\u001F') {
String ss = Integer.toHexString(ch);
sb.append("\\u");
for (int k = 0; k < 4 - ss.length(); k++) {
sb.append('0');
}
sb.append(ss.toUpperCase());
} else {
sb.append(ch);
}
}
}
return sb.toString();
}
public static String nullToJson() {
return "";
}
public static String objectToJson(Object obj) {
StringBuilder json = new StringBuilder();
if (obj == null) {
json.append("\"\"");
} else if (obj instanceof Number) {
json.append(numberToJson((Number) obj));
} else if (obj instanceof Boolean) {
json.append(booleanToJson((Boolean) obj));
} else if (obj instanceof String) {
json.append("\"").append(stringToJson(obj.toString())).append("\"");
} else if (obj instanceof Object[]) {
json.append(arrayToJson((Object[]) obj));
} else if (obj instanceof List) {
json.append(listToJson((List<?>) obj));
} else if (obj instanceof Map) {
json.append(mapToJson((Map<?, ?>) obj));
} else if (obj instanceof Set) {
json.append(setToJson((Set<?>) obj));
} else {
json.append(beanToJson(obj));
}
return json.toString();
}
public static String numberToJson(Number number) {
return number.toString();
}
public static String booleanToJson(Boolean bool) {
return bool.toString();
}
/** *//**
* @param bean
* bean对象
* @return String
*/
public static String beanToJson(Object bean) {
StringBuilder json = new StringBuilder();
json.append("{");
PropertyDescriptor[] props = null;
try {
props = Introspector.getBeanInfo(bean.getClass(), Object.class)
.getPropertyDescriptors();
} catch (IntrospectionException e) {
}
if (props != null) {
for (int i = 0; i < props.length; i++) {
try {
String name = objectToJson(props[i].getName());
String value = objectToJson(props[i].getReadMethod()
.invoke(bean));
json.append(name);
json.append(":");
json.append(value);
json.append(",");
} catch (Exception e) {
}
}
json.setCharAt(json.length() - 1, '}');
} else {
json.append("}");
}
return json.toString();
}
/** *//**
* @param list
* list对象
* @return String
*/
public static String listToJson(List<?> list) {
StringBuilder json = new StringBuilder();
json.append("[");
if (list != null && list.size() > 0) {
for (Object obj : list) {
json.append(objectToJson(obj));
json.append(",");
}
json.setCharAt(json.length() - 1, ']');
} else {
json.append("]");
}
return json.toString();
}
/** *//**
* @param array
* 对象数组
* @return String
*/
public static String arrayToJson(Object[] array) {
StringBuilder json = new StringBuilder();
json.append("[");
if (array != null && array.length > 0) {
for (Object obj : array) {
json.append(objectToJson(obj));
json.append(",");
}
json.setCharAt(json.length() - 1, ']');
} else {
json.append("]");
}
return json.toString();
}
/** *//**
* @param map
* map对象
* @return String
*/
public static String mapToJson(Map<?, ?> map) {
StringBuilder json = new StringBuilder();
json.append("{");
if (map != null && map.size() > 0) {
for (Object key : map.keySet()) {
json.append(objectToJson(key));
json.append(":");
json.append(objectToJson(map.get(key)));
json.append(",");
}
json.setCharAt(json.length() - 1, '}');
} else {
json.append("}");
}
return json.toString();
}
/** *//**
* @param set
* 集合对象
* @return String
*/
public static String setToJson(Set<?> set) {
StringBuilder json = new StringBuilder();
json.append("[");
if (set != null && set.size() > 0) {
for (Object obj : set) {
json.append(objectToJson(obj));
json.append(",");
}
json.setCharAt(json.length() - 1, ']');
} else {
json.append("]");
}
return json.toString();
}
}
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