jackson的应用
直接上代码
1 package com.demo.jackson.utils; 2 3 import com.fasterxml.jackson.core.JsonProcessingException; 4 import com.fasterxml.jackson.core.type.TypeReference; 5 import com.fasterxml.jackson.databind.DeserializationFeature; 6 import com.fasterxml.jackson.databind.JavaType; 7 import com.fasterxml.jackson.databind.ObjectMapper; 8 import lombok.extern.slf4j.Slf4j; 9 import org.springframework.util.StringUtils; 10 11 @Slf4j 12 public class JsonUtil { 13 private static ObjectMapper objectMapper = new ObjectMapper(); 14 static { 15 //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 16 objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false); 17 } 18 19 /** 20 * 对象转换成Sting 21 * @param obj 22 * @param <T> 23 * @return 24 */ 25 public static <T> String obj2String(T obj){ 26 if (obj == null) { 27 return null; 28 } 29 try { 30 return obj instanceof String ? (String) obj : objectMapper.writeValueAsString(obj); 31 } catch (JsonProcessingException e) { 32 System.out.println("Parse Object to String error"); 33 e.printStackTrace(); 34 return null; 35 } 36 } 37 /** 38 * 规范地将对象转换成Sting 39 * @param obj 40 * @param <T> 41 * @return 42 */ 43 public static <T> String obj2StringPretty(T obj){ 44 if(obj == null){ 45 return null; 46 } 47 try { 48 return obj instanceof String ? (String)obj : objectMapper.writerWithDefaultPrettyPrinter().writeValueAsString(obj); 49 } catch (Exception e) { 50 log.warn("Parse Object to String error",e); 51 return null; 52 } 53 } 54 55 /** 56 * String转换成obj对象 57 * @param str 58 * @param clazz 59 * @param <T> 60 * @return 61 */ 62 public static <T> T str2Obj(String str, Class<T> clazz){ 63 if(str==null){ 64 return null; 65 } 66 try { 67 return clazz.equals(String.class) ? (T) str : objectMapper.readValue(str, clazz); 68 } catch (Exception e) { 69 e.printStackTrace(); 70 return null; 71 } 72 } 73 74 /** 75 * String转换成对象 76 * @param str 77 * @param typeReference 78 * @param <T> 79 * @return 80 */ 81 public static <T> T string2Obj(String str, TypeReference<T> typeReference){ 82 if(StringUtils.isEmpty(str) || typeReference == null){ 83 return null; 84 } 85 try { 86 return (T)(typeReference.getType().equals(String.class)? str : objectMapper.readValue(str,typeReference)); 87 } catch (Exception e) { 88 log.warn("Parse String to Object error",e); 89 return null; 90 } 91 } 92 93 /** 94 * String转换成对象 95 * @param str 96 * @param collectionClass 97 * @param elementClasses 98 * @param <T> 99 * @return 100 */ 101 public static <T> T string2Obj(String str, Class<?> collectionClass, Class<?>... elementClasses){ 102 JavaType javaType = objectMapper.getTypeFactory().constructParametricType(collectionClass,elementClasses); 103 try { 104 return objectMapper.readValue(str,javaType); 105 } catch (Exception e) { 106 log.warn("Parse String to Object error",e); 107 return null; 108 } 109 } 110 }
测试：
1 package com.demo.jackson.test; 2 3 import com.demo.jackson.entity.Student; 4 import com.demo.jackson.utils.JsonUtil; 5 import com.fasterxml.jackson.core.type.TypeReference; 6 import com.fasterxml.jackson.databind.JsonNode; 7 import com.fasterxml.jackson.databind.ObjectMapper; 8 import org.junit.Test; 9 10 import java.util.*; 11 12 @SuppressWarnings("ALL") 13 public class JacksonTest { 14 /** 15 * 序列化 16 */ 17 @Test 18 public void test01(){ 19 Student s = new Student(); 20 s.setName("cjj"); 21 s.setAge(22); 22 s.setProfileImageUrl("link"); 23 String s1 = JsonUtil.obj2String(s); 24 System.out.println(s1); 25 26 Map<String, List<Integer>> map = new HashMap<>(); 27 map.put("a", Arrays.asList(1, 2, 3)); 28 map.put("b", Arrays.asList(1, 2, 3)); 29 String result1 = JsonUtil.obj2StringPretty(map); 30 System.out.println(result1); 31 } 32 33 /** 34 * 反序列化 35 */ 36 @Test 37 public void Test02(){ 38 String str = "{\"name\":\"name\",\"age\":10,\"profileImageUrl\":\"link\"}"; 39 Student student = JsonUtil.str2Obj(str, Student.class); 40 System.out.println(student); 41 } 42 @Test 43 public void test03() throws Exception { 44 45 Student student1 = new Student(); 46 student1.setAge(10); 47 student1.setName("name1"); 48 student1.setProfileImageUrl("link1"); 49 50 Student student2 = new Student(); 51 student2.setAge(20); 52 student2.setName("name2"); 53 student2.setProfileImageUrl("link2"); 54 55 List<Student> studentList = new ArrayList<>(); 56 studentList.add(student1); 57 studentList.add(student2); 58 String result = JsonUtil.obj2String(studentList); 59 // [{"name":"name1","age":10,"profileImageUrl":"link1"},{"name":"name2","age":20,"profileImageUrl":"link2"}] 60 System.out.println(result); 61 62 List<Student> finalList = JsonUtil.string2Obj(result, new TypeReference<List<Student>>() {}); 63 // [{name=name1, age=10, profileImageUrl=link1}, {name=name2, age=20, profileImageUrl=link2}] 64 System.out.println(finalList); 65 } 66 @Test 67 public void test04() throws Exception { 68 69 Student student1 = new Student(); 70 student1.setAge(10); 71 student1.setName("name1"); 72 student1.setProfileImageUrl("link1"); 73 74 Student student2 = new Student(); 75 student2.setAge(20); 76 student2.setName("name2"); 77 student2.setProfileImageUrl("link2"); 78 79 List<Student> studentList = new ArrayList<>(); 80 studentList.add(student1); 81 studentList.add(student2); 82 String result = JsonUtil.obj2String(studentList); 83 // [{"name":"name1","age":10,"profileImageUrl":"link1"},{"name":"name2","age":20,"profileImageUrl":"link2"}] 84 System.out.println(result); 85 86 List<Student> finalList = JsonUtil.string2Obj(result, List.class, Student.class); 87 // [{name=name1, age=10, profileImageUrl=link1}, {name=name2, age=20, profileImageUrl=link2}] 88 System.out.println(finalList); 89 } 90 @Test 91 public void jsonProperty() throws Exception { 92 93 String str = "{\"name\":\"name\",\"age\":10,\"setImage\":\"link\"}"; 94 Student student1 = JsonUtil.string2Obj(str, Student.class); 95 // name 96 System.out.println(student1.getName()); 97 // 10 98 System.out.println(student1.getAge()); 99 // link 100 System.out.println(student1.getProfileImageUrl()); 101 // {"name":"name","age":10,"getImage":"link"} 102 System.out.println(JsonUtil.obj2String(student1)); 103 } 104 105 /** 106 * 除了将json转为对象外，还可以用Tree Mode方式解析JSON，全程无脑操作， 107 * 除了一些特别复杂的JSON，或者只取JSON中的一部分，千万不要用这种二B方式解析JSON。 108 * 正确的方式是将JSON直接转为对象。 109 * @throws Exception 110 */ 111 @Test 112 public void parseJson() throws Exception { 113 String jsonStr = "{\"name\":\"zhansan\",\"age\":100,\"schools\":[{\"name\":\"tsinghua\",\"location\":\"beijing\"},{\"name\":\"pku\",\"location\":\"beijing\"}]}"; 114 115 ObjectMapper objectMapper = new ObjectMapper(); 116 JsonNode jsonNode = objectMapper.readTree(jsonStr); 117 118 String name = jsonNode.get("name").asText(); 119 int age = jsonNode.get("age").asInt(); 120 // name is zhansan age is 100 121 System.out.println("name is " + name + " age is " + age); 122 123 JsonNode schoolsNode = jsonNode.get("schools"); 124 for (int i = 0; i < schoolsNode.size(); i++) { 125 String schooleName = schoolsNode.get(i).get("name").asText(); 126 String schooleLocation = schoolsNode.get(i).get("location").asText(); 127 // schooleName is tsinghua schooleLocation is beijing 128 // schooleName is pku schooleLocation is beijing 129 System.out.println("schooleName is " + schooleName + " schooleLocation is " + schooleLocation); 130 } 131 } 132 }
