jackson工具类 对象转字符串 -- 字符串转对象

这个一个json的工具类。用的是jackson，当然还有谷歌的gosn，阿里的fastjson ，但是jackson的感觉还是最成熟（网上大神说的。。。）

实现的功能很简单，对象转字符串  字符串转简单对象  转list<T>复杂对象  还包括时间格式化工具类 直接都能用。。。不用纠结原理咋实现！！！

先上依赖

<dependencies>
        <!--json格式化工具类-->
        <dependency>
            <groupId>org.codehaus.jackson</groupId>
            <artifactId>jackson-mapper-asl</artifactId>
            <version>1.9.12</version>
        </dependency>
        <!--时间工具类-->
        <dependency>
            <groupId>joda-time</groupId>
            <artifactId>joda-time</artifactId>
            <version>2.3</version>
        </dependency>
        <!--apache工具类-->
        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-lang3</artifactId>
            <version>3.5</version>
        </dependency>

        <!--加速开发的工具，可以省略getset和日志类，只需要注解就可以-->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.16.6</version>
        </dependency>
        <!--日志相关-->
        <dependency>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-classic</artifactId>
            <version>1.1.2</version>
            <scope>compile</scope>
        </dependency>
        <dependency>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-core</artifactId>
            <version>1.1.2</version>
            <scope>compile</scope>
        </dependency>
        <dependency>
            <groupId>org.logback-extensions</groupId>
            <artifactId>logback-ext-spring</artifactId>
            <version>0.1.1</version>
        </dependency>
    </dependencies>

JsonUtil.java

import lombok.extern.slf4j.Slf4j;
import org.apache.commons.lang3.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.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

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

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

        //取消默认转换timestamps形式
        objectMapper.configure(SerializationConfig.Feature.WRITE_DATES_AS_TIMESTAMPS,false);

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

        //所有的日期格式都统一为以下的样式，即yyyy-MM-dd HH:mm:ss
        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);
    }

    //对象转json字符串
    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;
        }
    }
    //对象转json字符串 重载方法 格式化的jaon字符串 方便调试 实际开发取第一种方法
    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;
        }
    }

    //json字符串转对象转
    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;
        }
    }

    //json字符串转list<T>对象  和下面的一样
    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;
        }
    }

    //json字符串转list<T>对象   和上面的一样
    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 static void main(String[] args) {

        User user = new User();
        user.setAge(12);
        user.setId(1);
        user.setName("刘中华");
        String s = JsonUtil.obj2String(user);
        System.out.println(s);
        System.out.println("----------------------------------");
        //--------------------------------------
        System.out.println(JsonUtil.string2Obj(s,User.class));
        System.out.println("----------------------------------");
        //--------------------------------------
        ArrayList<User> users = new ArrayList<>();
        users.add(new User(1,"a",1));
        users.add(new User(2,"b",2));
        users.add(new User(3,"c",3));
        String s1 = JsonUtil.obj2String(users);
        System.out.println(s1);
        System.out.println("----------------------------------");
        //--------------------------------------
        System.out.println(JsonUtil.string2Obj(s1,new TypeReference<List<User>>(){}));
        System.out.println("----------------------------------");
        //--------------------------------------
        List<User> userListObj2 = JsonUtil.string2Obj(s1,List.class,User.class);
        System.out.println(userListObj2);

    }

}

User.java

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import lombok.ToString;

/**
 * Created by 敲代码的卡卡罗特
 * on 2018/4/6 15:59.
 */
@Data
@ToString
@AllArgsConstructor
@NoArgsConstructor
public class User {
    private Integer id;
    private String name;
    private Integer age;
}

DateTimeUtil.java

import org.apache.commons.lang3.StringUtils;
import org.joda.time.DateTime;
import org.joda.time.format.DateTimeFormat;
import org.joda.time.format.DateTimeFormatter;

import java.util.Date;

/**
 * Created by geely
 */
public class DateTimeUtil {

    //joda-time

    //str->Date
    //Date->str
    public static final String STANDARD_FORMAT = "yyyy-MM-dd HH:mm:ss";

    //字符串转日期
    public static Date strToDate(String dateTimeStr,String formatStr){
        DateTimeFormatter dateTimeFormatter = DateTimeFormat.forPattern(formatStr);
        DateTime dateTime = dateTimeFormatter.parseDateTime(dateTimeStr);
        return dateTime.toDate();
    }
    //日期转字符串
    public static String dateToStr(Date date,String formatStr){
        if(date == null){
            return StringUtils.EMPTY;
        }
        DateTime dateTime = new DateTime(date);
        return dateTime.toString(formatStr);
    }
    //如果不写格式，则取默认格式
    public static Date strToDate(String dateTimeStr){
        DateTimeFormatter dateTimeFormatter = DateTimeFormat.forPattern(STANDARD_FORMAT);
        DateTime dateTime = dateTimeFormatter.parseDateTime(dateTimeStr);
        return dateTime.toDate();
    }
    //如果不写格式，则取默认格式
    public static String dateToStr(Date date){
        if(date == null){
            return StringUtils.EMPTY;
        }
        DateTime dateTime = new DateTime(date);
        return dateTime.toString(STANDARD_FORMAT);
    }

    public static void main(String[] args) {
        System.out.println(DateTimeUtil.dateToStr(new Date(),"yyyy-MM-dd HH:mm:ss"));
        System.out.println(DateTimeUtil.strToDate("2010-01-01 11:11:11","yyyy-MM-dd HH:mm:ss"));

    }

}