使用ObjectMapper实现JSON与JavaBean的高效转换

ObjectMapper 介绍&＃xff1a;

Jackson可以轻松的将Java对象转换成json对象和xml文档&＃xff0c;同样也可以将json、xml、文件等转换成Java对象。它使用JsonParser和JsonGenerator的实例实现JSON实际的读/写。

Jackson主要包含了3个模块&＃xff1a;

jackson-core
jackson-annotations
jackson-databind
其中&＃xff0c;jackson-annotations依赖于jackson-core&＃xff0c;jackson-databind又依赖于jackson-annotations。

Jackson有三种方式处理Json&＃xff1a;

使用底层的基于Stream的方式对Json的每一个小的组成部分进行控制
使用Tree Model&＃xff0c;通过JsonNode处理单个Json节点
使用databind模块&＃xff0c;直接对Java对象进行序列化和反序列化
通常来说&＃xff0c;我们在日常开发中使用的是第3种方式&＃xff0c;有时为了简便也会使用第2种方式&＃xff0c;比如你要从一个很大的Json对象中只读取那么一两个字段的时候&＃xff0c;采用databind方式显得有些重&＃xff0c;JsonNode反而更简单。

加入依赖

<dependency><groupId>com.fasterxml.jackson.core</groupId><artifactId>jackson-databind</artifactId><version>2.8.3</version></dependency>


import java.io.File;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationFeature;public class ObjectMapperDemo {
public static void main(String[] args) throws Exception {/*testObj();*//*testList();*/testMap();}/*** 1.对象转json格式的字符串* 2.对象转字节数组* 3.json字符串转为对象* 4.byte数组转为对象 * &＃64;throws Exception*/public static void testObj() throws Exception {//创建转换对象 使用默认的构造方法&＃xff0c;使用的是JsonParsers和JsonGenerators映射ObjectMapper mapper&＃61;new ObjectMapper();// 转换为格式化的jsonmapper.enable(SerializationFeature.INDENT_OUTPUT);// 如果json中有新增的字段并且是实体类类中不存在的&＃xff0c;不报错mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);//创建学生对象Student stu&＃61;new Student("ghl", 12, "123", "19845252&＃64;qq.com");//1.对象转json格式的字符串String stuToString &＃61; mapper.writeValueAsString(stu);//System.out.println("对象转为字符串&＃xff1a;" &＃43; stuToString);/** 输出结果&＃xff1a;* 对象转为字符串&＃xff1a;{"name" : "ghl","age" : 12,"password" : "123","email" : "19845252&＃64;qq.com"}*///2.对象转字节数组byte[] byteArr &＃61; mapper.writeValueAsBytes(stu);System.out.println("对象转为byte数组&＃xff1a;" &＃43; byteArr);/** 对象转为byte数组&＃xff1a;[B&＃64;6aaa5eb0*///3.json字符串转为对象Student student &＃61; mapper.readValue(stuToString, Student.class);System.out.println("json字符串转为对象&＃xff1a;" &＃43; student);//json字符串转为对象&＃xff1a;Student [name&＃61;ghl, age&＃61;12, password&＃61;123, email&＃61;19845252&＃64;qq.com]//4.byte数组转为对象 Student student2 &＃61; mapper.readValue(byteArr, Student.class);System.out.println("byte数组转为对象&＃xff1a;" &＃43; student2);//输出结果&＃xff1a;byte数组转为对象&＃xff1a;Student [name&＃61;ghl, age&＃61;12, password&＃61;123, email&＃61;19845252&＃64;qq.com]mapper.writeValue(new File("D:/test.txt"), stu); // 写到文件中}/**list集合与json字符的转换* 1.集合转为字符串* 2.字符串转集合* &＃64;throws Exception * */public static void testList() throws Exception {//创建转换对象 使用默认的构造方法&＃xff0c;使用的是JsonParsers和JsonGenerators映射ObjectMapper mapper&＃61;new ObjectMapper();// 转换为格式化的jsonmapper.enable(SerializationFeature.INDENT_OUTPUT);// 如果json中有新增的字段并且是实体类类中不存在的&＃xff0c;不报错mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);List<Student> studnetList &＃61; new ArrayList<Student>();studnetList.add(new Student("zs", 12, "121", "1584578878&＃64;qq.com"));studnetList.add(new Student("lisi", 13, "122", "1584578878&＃64;qq.com"));studnetList.add(new Student("wangwu", 14, "123", "1584578878&＃64;qq.com"));studnetList.add(new Student("zhangliu", 15, "124", "1584578878&＃64;qq.com"));//1.集合转为字符串String jsonStr &＃61; mapper.writeValueAsString(studnetList);System.out.println("集合转为字符串&＃xff1a;" &＃43; jsonStr);/*輸出結果* 集合转为字符串&＃xff1a;[ {"name" : "zs","age" : 12,"password" : "121","email" : "1584578878&＃64;qq.com"}, {"name" : "lisi","age" : 13,"password" : "122","email" : "1584578878&＃64;qq.com"}, {"name" : "wangwu","age" : 14,"password" : "123","email" : "1584578878&＃64;qq.com"}, {"name" : "zhangliu","age" : 15,"password" : "124","email" : "1584578878&＃64;qq.com"} ]* *///2.字符串转集合List<Student> userListDes &＃61; mapper.readValue(jsonStr, List.class);System.out.println("字符串转集合&＃xff1a;" &＃43; userListDes);/*輸出結果* 字符串转集合&＃xff1a;[{name&＃61;zs, age&＃61;12, password&＃61;121, email&＃61;1584578878&＃64;qq.com}, * {name&＃61;lisi, age&＃61;13, password&＃61;122, email&＃61;1584578878&＃64;qq.com}, * {name&＃61;wangwu, age&＃61;14, password&＃61;123, email&＃61;1584578878&＃64;qq.com}, * {name&＃61;zhangliu, age&＃61;15, password&＃61;124, email&＃61;1584578878&＃64;qq.com}]*/}/**Map与字符串转换* 1.Map转为字符串* 2.字符串转Map* &＃64;throws Exception*/public static void testMap() throws Exception {//创建转换对象 使用默认的构造方法&＃xff0c;使用的是JsonParsers和JsonGenerators映射ObjectMapper mapper&＃61;new ObjectMapper();// 转换为格式化的jsonmapper.enable(SerializationFeature.INDENT_OUTPUT);// 如果json中有新增的字段并且是实体类类中不存在的&＃xff0c;不报错mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);Map<String, Object> testMap &＃61; new HashMap<String, Object>();testMap.put("name", "ghl");testMap.put("age", 18);//1.Map转为字符串String jsonStr &＃61; mapper.writeValueAsString(testMap);System.out.println("Map转为字符串&＃xff1a;" &＃43; jsonStr);/** Map转为字符串&＃xff1a;{"name" : "ghl","age" : 18}*///2.字符串转MapMap<String, Object> testMapDes &＃61; mapper.readValue(jsonStr, Map.class);System.out.println("字符串转Map&＃xff1a;" &＃43; testMapDes);/** 字符串转Map&＃xff1a;{name&＃61;ghl, age&＃61;18}*/}
}

工具类


import java.util.ArrayList;
import java.util.List;import com.alibaba.fastjson.JSON;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JavaType;
import com.fasterxml.jackson.databind.ObjectMapper;public class JsonUtils {// 定义jackson对象private static final ObjectMapper MAPPER &＃61; new ObjectMapper();/*** 将对象转换成json字符串&＃xfffd;??*

Title: pojoToJson