JAVA中，各种数据转换为对象的原理
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2024-02-10 08:32:24
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package com.it.code.req_string_map_obj;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import javax.servlet.http.HttpServletRequest;
public class demo002 {
/**
* 把对象toString
*
* @param object 对象
* @return 对象转换为String的类型
* @throws Exception
*/
public static String toString(Object object) {
if (object == null) {
return null;
}
StringBuffer sb = new StringBuffer();
Class c = object.getClass();
Method[] methods = c.getMethods();
Field[] fields = c.getDeclaredFields();
String fieldName, methodName;
Method method;
Field field;
for (int i = 0; i < fields.length; i++) {
field = fields[i];
fieldName = field.getName();
for (int j = 0; j < methods.length; j++) {
method = methods[j];
methodName = method.getName();
if (methodName.toUpperCase().endsWith("GET" + fieldName.toUpperCase())) {
try {
sb.append(fieldName + "=" + method.invoke(object));
} catch (Exception e) {
System.out.println("映射新对象" + c + "失败，列名:" + fieldName + "，方法名:" + methodName + "/n" + e);
}
break;
}
}
if (i < fields.length - 1) {
sb.append(",");
}
}
return sb.toString();
}
//测试tostring
public static void main01(String[] args) {
Person person = new Person();
person.setId("001");
person.setName("002");
System.out.println(toString(person));
}
//测试基类
static class Person {
private String id;
private String name ;
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;
}
}
/**
* 把String类型转换成map（只需键值对）
*
* @param stringByMap 键值对的形式，中间用英文逗号分隔
* @return map
*/
public static Map refertForMap(String stringByMap) {
// 验证输入，若是空，返回null
/* if (Validate.isNull(stringByMap)) {
return null;
}*/
// 根据“,”分隔开每一组数值
String[] keyValues = stringByMap.split(",");
// 定义返回类型
Map map = new HashMap();
for (int i = 0; i < keyValues.length; i++) {
// 根据“=”分隔开key和value值
// 存放每一组数值
String[] key_value = keyValues[i].split("=");
// 如果不存在key或value则继续下次组装
if (key_value.length != 2) {
continue;
}
// 存放key和value
//网站认证中心
String key;
// 把key值去除空格，并转成大写
try {
key = key_value[0].trim().toUpperCase();
} catch (RuntimeException e) {
continue;
}
// 获取value值
String value = key_value[1];
// 存入map
map.put(key, value);
}
// 返回map
return map;
}
//测试
public static void main02(String[] args) {
String string = "id=1,name=2";
Map<String, Object> map =refertForMap(string);
for(String key:map.keySet()){
System.out.println(key+"="+map.get(key));
}
}
/**
* 把String类型转换成对象
*
* @param stringByObject 键值对的形式，中间用英文逗号分隔
* @param obj 要映射的对象
* @return Object 映射后的对象
* @throws Exception
*/
public static Object refertForObject(String stringByObject, Object obj) {
if ("java.lang.Class".equals(obj.getClass().getName())) {
System.out.println("Object不应为java.lang.Class类型");
}
// 验证输入，若是空，返回null
/* if (Validate.isNull(stringByObject)) {
return null;
}*/
// 根据“,”分隔开每一组数值
String[] keyValues = stringByObject.split(",");
// 存放key和value
String key, value;
// 定义返回类型
for (int i = 0; i < keyValues.length; i++) {
// 根据“=”分隔开key和value值
// 存放每一组数值
String[] key_value = keyValues[i].split("=");
// 如果不存在key或value则继续下次组装
if (key_value.length != 2) {
continue;
}
// 把key值去除空格，并转成大写
try {
key = key_value[0].trim().toUpperCase();
} catch (RuntimeException e) {
continue;
}
// 获取value值
value = key_value[1];
// 存入map
setObject(key, value, obj);
}
// 返回map
return obj;
}
//
public static void main(String[] args) {
String string = "id=1,name=2";
Person person = new Person();
person =(Person)refertForObject(string,person);
System.out.println(person.getId());
System.out.println(person.getName());
}
/**
* 把request映射成map
*
* @param request
* @return
* @throws RefertException
*/
public static Map refertForMapByRequest(HttpServletRequest request) {
// 存放符合条件的name-value映射值
Map initMap = new HashMap();
try {
// 获取页面上的所有name值
Enumeration pNames = request.getParameterNames();
// 获取页面的操作类型
// 遍历页面所有的name值
while (pNames.hasMoreElements()) {
// 获取当前要验证的name值
String name = (String) pNames.nextElement();
String value = request.getParameter(name);
initMap.put(name.toUpperCase(), value);
}
// 返回map
return initMap;
} catch (Exception e) {
System.out.println("获取页面信息失败\n" + e);
return initMap;
}
}
/**
* 把request映射成Object
*
* @param request
* @param obj
* @return
* @throws RefertException
*/
public static Object refertForObjectByRequest(HttpServletRequest request, Object obj) {
try {
Map map = refertForMapByRequest(request);
refertForObjectByMap(map, obj);
return obj;
} catch (Exception e) {
System.out.println(e);
return obj;
}
}
/**
* 把Object映射成Map
*
* @param object
* @return
* @throws RefertException
*/
public static Map<String, Object> refertForMapByObject(Object object) {
if (object == null) {
return null;
}
Map<String, Object> map = new HashMap<String, Object>();
Class c = object.getClass();
Method[] methods = c.getMethods();
Field[] fields = c.getDeclaredFields();
String fieldName, methodName;
Method method;
Field field;
for (int i = 0; i < fields.length; i++) {
field = fields[i];
fieldName = field.getName();
for (int j = 0; j < methods.length; j++) {
method = methods[j];
methodName = method.getName();
if (methodName.toUpperCase().endsWith("GET" + fieldName.toUpperCase())) {
try {
map.put(fieldName, method.invoke(object));
} catch (Exception e) {
System.out.println("映射新对象" + c + "失败，列名:" + fieldName + "，方法名:" + methodName + "/n" + e);
}
break;
}
}
}
return map;
}
/**
* 把map映射成对象
*
* @param map 映射源内容
* @param obj 映射成的对象
* @return obj
* @throws RefertException
*/
public static Object refertForObjectByMap(Map<Object, Object> map, Object obj) {
try {
//验证
/* if (Validate.isNull(map))
return null;
if (Validate.isNull(obj))
return null;*/
if ("java.lang.Class".equals(obj.getClass().getName()))
System.out.println("Object不应为java.lang.Class类型");
for (Map.Entry<Object, Object> e : map.entrySet()) {
String key = e.getKey().toString();
Object value = e.getValue();
setObject(key, value, obj);
}
return obj;
} catch (Exception e) {
System.out.println(e);
return obj;
}
}
/**
* 映射对象
*
* @param name 映射的名称
* @param value 映射的值
* @param obj 映射的对象
* @return 映射完成的对象
* @throws RefertException
*/
private static Object setObject(String name, Object value, Object obj) {
Class c = obj.getClass();
String setName;
name = "SET" + name;
name = name.toUpperCase();
Method[] methods = c.getDeclaredMethods();
Method method;
String valueType = value.getClass().getName();
for (int i = 0; i < methods.length; i++) {
method = methods[i];
setName = method.getName().toUpperCase();
if (name.equals(setName)) {
Class[] pts = method.getParameterTypes();
if (pts.length != 1) {
System.out.println("映射新对象" + c + "失败,name=" + name + "的传入参数不唯一，映射失败\n");
}
String parameterType = pts[0].getTypeName();
if (parameterType.equals(valueType)) {
// 对象接收值类型与传入值类型相同
} else if ("java.util.Map".equals(parameterType) && Map.class.isAssignableFrom(value.getClass())) {
// 对象接收值类型map是传入值的父类
} else if ("java.util.List".equals(parameterType) && List.class.isAssignableFrom(value.getClass())) {
// 对象接收值类型list是传入值的父类
} else if ("java.lang.Object".equals(parameterType)) {
// 对象接收值类型object
} else if ("java.lang.String".equals(value.getClass().getName())) {
try {
if ("byte".equals(parameterType)) {
value = Byte.valueOf((String) value);
} else if ("short".equals(parameterType)) {
value = Short.valueOf((String) value);
} else if ("int".equals(parameterType)) {
value = Integer.valueOf((String) value);
} else if ("long".equals(parameterType)) {
value = Long.valueOf((String) value);
} else if ("float".equals(parameterType)) {
value = Float.valueOf((String) value);
} else if ("double".equals(parameterType)) {
value = Double.valueOf((String) value);
} else if ("char[]".equals(parameterType)) {
value = value.toString().toCharArray();
} else if ("boolean".equals(parameterType)) {
value = Boolean.valueOf((String) value);
} else if ("double".equals(parameterType)) {
value = Double.valueOf((String) value);
} else {
// map不支持（map内嵌套map，对map根据逗号进行拆分时出错）
System.out.println();
}
} catch (Exception e) {
StringBuffer refertLogger = new StringBuffer();
refertLogger.append("映射新对象" + c + "失败,");
refertLogger.append("name=" + name + ",");
refertLogger.append(valueType + "强转为" + parameterType + "失败");
System.out.println(refertLogger.toString());
}
} else {
StringBuffer refertLogger = new StringBuffer();
refertLogger.append("映射新对象" + c + "失败,");
refertLogger.append("name=" + name + ",");
refertLogger.append(valueType + "强转为" + parameterType + "失败");
System.out.println(refertLogger.toString());
}
try {
method.invoke(obj, value);
break;
} catch (Exception e) {
StringBuffer refertLogger = new StringBuffer();
refertLogger.append("映射新对象" + c + "失败,");
refertLogger.append("name=" + name + "。");
System.out.println(refertLogger.toString());
}
}
}
return obj;
}
}