对象与字符串相互转换

import com.google.common.collect.Lists;
import com.mmall.pojo.Category;
import com.mmall.pojo.TestPojo;
import com.mmall.pojo.User;
import lombok.extern.slf4j.Slf4j;
import org.apache.commons.lang.StringUtils;
import org.codehaus.jackson.map.DeserializationConfig;
import org.codehaus.jackson.map.ObjectMapper;
import org.codehaus.jackson.map.SerializationConfig;
import org.codehaus.jackson.map.annotate.JsonSerialize.Inclusion;
import org.codehaus.jackson.type.JavaType;
import org.codehaus.jackson.type.TypeReference;

import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
* Created by geely
*/
@Slf4j
public class JsonUtil {

private static ObjectMapper objectMapper = new ObjectMapper();
static{
//1   对象的所有字段全部列入
objectMapper.setSerializationInclusion(Inclusion.ALWAYS);

//2      取消默认转换timestamps形式
//timestamps   时间戳     1521353913377
// true时为date转化为timestamps
//false时为  2018-03-18T06:20:21.045+0000
objectMapper.configure(SerializationConfig.Feature.WRITE_DATES_AS_TIMESTAMPS,false);

//3     忽略空Bean转json的错误
objectMapper.configure(SerializationConfig.Feature.FAIL_ON_EMPTY_BEANS,false);

//4     所有的日期格式都统一为以下的样式，即yyyy-MM-dd HH:mm:ss  4的优先级大于2
objectMapper.setDateFormat(new SimpleDateFormat(DateTimeUtil.STANDARD_FORMAT));

//  忽略 在json字符串中存在，但是在java对象中不存在对应属性的情况。防止错误
objectMapper.configure(DeserializationConfig.Feature.FAIL_ON_UNKNOWN_PROPERTIES,false);
}

public static <T> String obj2String(T obj){
if(obj == null){
return null;
}
try {
return obj instanceof String ? (String)obj :  objectMapper.writeValueAsString(obj);
} catch (Exception e) {
log.warn("Parse Object to String error",e);
return null;
}
}

public static <T> String obj2StringPretty(T obj){
if(obj == null){
return null;
}
try {
return obj instanceof String ? (String)obj :  objectMapper.writerWithDefaultPrettyPrinter().writeValueAsString(obj);
} catch (Exception e) {
log.warn("Parse Object to String error",e);
return null;
}
}

public static <T> T string2Obj(String str,Class<T> clazz){
if(StringUtils.isEmpty(str) || clazz == null){
return null;
}

try {
return clazz.equals(String.class)? (T)str : objectMapper.readValue(str,clazz);
} catch (Exception e) {
log.warn("Parse String to Object error",e);
return null;
}
}

public static <T> T string2Obj(String str, TypeReference<T> typeReference){
if(StringUtils.isEmpty(str) || typeReference == null){
return null;
}
try {
return (T)(typeReference.getType().equals(String.class)? str : objectMapper.readValue(str,typeReference));
} catch (Exception e) {
log.warn("Parse String to Object error",e);
return null;
}
}

public static <T> T string2Obj(String str,Class<?> collectionClass,Class<?>... elementClasses){
JavaType javaType = objectMapper.getTypeFactory().constructParametricType(collectionClass,elementClasses);
try {
return objectMapper.readValue(str,javaType);
} catch (Exception e) {
log.warn("Parse String to Object error",e);
return null;
}
}

public
4000
static void main(String[] args) {
//        TestPojo testPojo = new TestPojo();
//        testPojo.setName("Geely");
//        testPojo.setId(666);
//
//        //{"name":"Geely","id":666}
String json = "{\"name\":\"Geely\",\"color\":\"blue\",\"id\":666}";
TestPojo testPojoObject = JsonUtil.string2Obj(json,TestPojo.class);
//        String testPojoJson = JsonUtil.obj2String(testPojo);
//        log.info("testPojoJson:{}",testPojoJson);

//        log.info("end");
//
User user = new User();
user.setId(2);
user.setEmail("geely@happymmall.com");
user.setCreateTime(new Date());
String userJsonPretty = JsonUtil.obj2StringPretty(user);
log.info("userJson:{}",userJsonPretty);

//        User u1 = new User();
//        u1.setId(1);
//        u1.setEmail("geelyu2@happymmall.com");
//
//        User u2 = new User();
//        u2.setId(1);
//        u2.setEmail("geelyu2@happymmall.com");
//
//
//
//        String user1Json = JsonUtil.obj2String(u1);
//
//        String user1JsonPretty = JsonUtil.obj2StringPretty(u1);
//
//        log.info("user1Json:{}",user1Json);
//
//        log.info("user1JsonPretty:{}",user1JsonPretty);
//
//
//        User user = JsonUtil.string2Obj(user1Json,User.class);
//
//        List<User> userList = Lists.newArrayList();
//        userList.add(u1);
//        userList.add(u2);
//
//        String userListStr = JsonUtil.obj2StringPretty(userList);
//
//        log.info("==================");
//
//        log.info(userListStr);
//
//        List<User> userListObj1 = JsonUtil.string2Obj(userListStr, new TypeReference<List<User>>() {
//        });
//
//
//        List<User> userListObj2 = JsonUtil.string2Obj(userListStr,List.class,User.class);
//
//        System.out.println("end");

}