275 lines
9.5 KiB
Java
275 lines
9.5 KiB
Java
package icbc;
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import java.lang.reflect.Field;
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import java.util.Arrays;
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import java.util.HashMap;
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import java.util.List;
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import java.util.Map;
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import static jdk.nashorn.internal.runtime.regexp.joni.Config.DEBUG;
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/**
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* @Author: Alawn
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* @Description:
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* @Date: Create in 下午4:52 2021/3/5
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*/
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public class BeanToJson {
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//需要解决的问题
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//1.怎么获取字段名,怎么获取字段的值
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//2.怎么判断是基本类型,基本类型的值,不需要加隐含
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//3.怎么判断是常用的类型,如果是常用类型里面的集合话,需要递归判断
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//4.如何判断是自定义的bean对象 如果是自定义的bean对象,需要再次进行解析,
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//5.数组的话,需要遍历展示
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//6.将key按照ascii码升序排列
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//修改部分:原文存在bug.当类型为数组类型的时候,会出现问题, 以修正为需要的逻辑
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public static <T> String toJson(T t) {
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if (t == null) {
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return "{}";
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}
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return beanToJson(t);
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}
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public static <T> String beanToJson(T t) {
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//先获取所有字段名
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Field[] fields = t.getClass().getDeclaredFields();
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String[] keys = new String[fields.length];
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for (int i = 0; i < fields.length; i++) {
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keys[i] = fields[i].getName();
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}
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//获取按照Ascii排序之后的顺序
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keys = getUrlParam(keys);
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StringBuilder sb = new StringBuilder();
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sb.append("{");
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Map<String, Field> map = new HashMap<>();
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for (int i = 0; i < keys.length; i++) {
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for (Field field : fields) {
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if (field.getName().equals(keys[i])) {
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map.put(keys[i], field);
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// 当方法名满足键值得时候结束当前层循环
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continue;
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}
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}
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}
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for (String name : keys) {
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Field field = map.get(name);
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field.setAccessible(true);
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Class<?> type = field.getType();
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Object value = null;
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try {
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value = field.get(t);
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} catch (IllegalAccessException e) {
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e.printStackTrace();
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}
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// 内部类的外部类引用(指针)字段
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if (name.contains("this$")) {
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continue;
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}
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String typeName = type.getName();
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if (typeName.equals("java.lang.String")) {
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try {
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sb.append("\"" + name + "\":");
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sb.append(stringToJson((String) field.get(t)));
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sb.append(",");
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} catch (Exception e) {
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if (DEBUG) {
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e.printStackTrace();
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}
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}
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} else if (typeName.equals("boolean") ||
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typeName.equals("java.lang.Boolean") ||
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typeName.equals("int") ||
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typeName.equals("java.lang.Integer") ||
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typeName.equals("float") ||
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typeName.equals("java.lang.Float") ||
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typeName.equals("double") ||
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typeName.equals("java.lang.Double") ||
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typeName.equals("long") ||
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typeName.equals("java.lang.Long")) {
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try {
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sb.append("\"" + name + "\":");
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sb.append(field.get(t));
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sb.append(",");
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} catch (Exception e) {
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if (DEBUG) {
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e.printStackTrace();
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}
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}
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} else if (typeName.equals("java.util.List") ||
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typeName.equals("java.util.ArrayList")) {
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try {
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List<?> objList = (List<?>) field.get(t);
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if (null != objList && objList.size() > 0) {
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sb.append("\"" + name + "\":");
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sb.append("[");
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String toJson = listToJson((List<?>) field.get(t));
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sb.append(toJson);
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sb.setCharAt(sb.length() - 1, ']');
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sb.append(",");
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}
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} catch (Exception e) {
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if (DEBUG) {
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e.printStackTrace();
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}
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}
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} else if (value.getClass().isArray()) {
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Object[] arr = (Object[]) value; // 装换成数组
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List list = Arrays.asList(arr);
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try {
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if (null != list && list.size() > 0) {
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sb.append("\"" + name + "\":");
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sb.append("[");
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String toJson = listToJson(list);
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sb.append(toJson);
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sb.setCharAt(sb.length() - 1, ']');
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sb.append(",");
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}
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} catch (Exception e) {
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if (DEBUG) {
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e.printStackTrace();
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}
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}
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} else {
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try {
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sb.append("\"" + name + "\":");
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sb.append("{");
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sb.append(beanToJson(field.get(t)));
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sb.setCharAt(sb.length() - 1, '}');
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sb.append(",");
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} catch (Exception e) {
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if (DEBUG) {
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e.printStackTrace();
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}
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}
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}
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}
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if (sb.length() == 1) {
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sb.append("}");
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}
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sb.setCharAt(sb.length() - 1, '}');
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return sb.toString();
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}
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/**
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* 将 List 对象编码为 JSON格式
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*
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* @param objList 待封装的对象集合
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* @return String:封装后JSONArray String格式
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* @version 1.0
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*/
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private static <T> String listToJson(List<T> objList) {
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final StringBuilder sb = new StringBuilder();
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for (T t : objList) {
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if (t instanceof String) {
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sb.append(stringToJson((String) t));
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sb.append(",");
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} else if (t instanceof Boolean ||
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t instanceof Integer ||
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t instanceof Float ||
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t instanceof Double) {
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sb.append(t);
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sb.append(",");
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} else {
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sb.append(beanToJson(t));
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sb.append(",");
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}
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}
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return sb.toString();
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}
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/**
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* 将 String 对象编码为 JSON格式，只需处理好特殊字符
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*
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* @param str String 对象
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* @return String:JSON格式
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* @version 1.0
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*/
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private static String stringToJson(final String str) {
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if (str == null || str.length() == 0) {
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return "\"\"";
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}
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final StringBuilder sb = new StringBuilder();
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sb.append('\"');
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for (int i = 0; i < str.length(); i++) {
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final char c = str.charAt(i);
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sb.append(c == '\"' ? "\\\"" : c == '\\' ? "\\\\"
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: c == '/' ? "\\/" : c == '\b' ? "\\b" : c == '\f' ? "\\f"
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: c == '\n' ? "\\n" : c == '\r' ? "\\r"
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: c == '\t' ? "\\t" : c + "");
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}
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sb.append('\"');
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return sb.toString();
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}
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/**
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* 对字符串数组进行排序
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*
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* @param keys
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* @return
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*/
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private static String[] getUrlParam(String[] keys) {
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for (int i = 0; i < keys.length - 1; i++) {
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for (int j = 0; j < keys.length - i - 1; j++) {
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String pre = keys[j];
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String next = keys[j + 1];
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if (isMoreThan(pre, next)) {
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String temp = pre;
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keys[j] = next;
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keys[j + 1] = temp;
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}
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}
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}
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return keys;
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}
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/**
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* 比较两个字符串的大小，按字母的ASCII码比较
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*
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* @param pre
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* @param next
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* @return
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*/
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private static boolean isMoreThan(String pre, String next) {
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if (null == pre || null == next || "".equals(pre) || "".equals(next)) {
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return false;
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}
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char[] c_pre = pre.toCharArray();
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char[] c_next = next.toCharArray();
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int minSize = Math.min(c_pre.length, c_next.length);
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for (int i = 0; i < minSize; i++) {
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if ((int) c_pre[i] > (int) c_next[i]) {
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return true;
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} else if ((int) c_pre[i] < (int) c_next[i]) {
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return false;
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}
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}
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if (c_pre.length > c_next.length) {
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return true;
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}
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return false;
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}
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}
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