JSON 之 jackson 用法
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Jackson简单用法一：
importjava.text.SimpleDateFormat;
importjava.util.ArrayList;
importjava.util.Date;
importjava.util.HashMap;
importjava.util.List;
importjava.util.Map;
import org.codehaus.jackson.JsonGenerator;
importorg.codehaus.jackson.map.DeserializationConfig;
importorg.codehaus.jackson.map.ObjectMapper;
import org.codehaus.jackson.map.SerializationConfig;
importorg.codehaus.jackson.map.annotate.JsonSerialize.Inclusion;
importorg.codehaus.jackson.type.TypeReference;
import com.fasterxml.jackson.databind.DeserializationFeature;
import java.util.Date;
public classJacksonTest {
public staticObjectMapper getDefaultObjectMapper() {
ObjectMapper mapper = new ObjectMapper();
//设置将对象转换成JSON字符串时候:包含的属性不能为空或"";
//Include.Include.ALWAYS 默认
//Include.NON_DEFAULT 属性为默认值不序列化
//Include.NON_EMPTY 属性为空（""） 或者为 NULL 都不序列化
//Include.NON_NULL 属性为NULL不序列化
mapper.setSerializationInclusion(Inclusion.NON_EMPTY);
//设置将MAP转换为JSON时候只转换值不等于NULL的
mapper.configure(SerializationConfig.Feature.WRITE_NULL_MAP_VALUES,false);
mapper.setDateFormat(newSimpleDateFormat("yyyy-MM-ddHH:mm:ss"));
// mapper.configure(JsonGenerator.Feature.ESCAPE_NON_ASCII, true);
//设置有属性不能映射成PO时不报错
mapper.disable(DeserializationConfig.Feature.FAIL_ON_UNKNOWN_PROPERTIES);
// mapper.configure(DeserializationConfig.Feature.FAIL_ON_UNKNOWN_PROPERTIES,false); 上一条也可以如此设置；
returnmapper;
}
public static voidmain(String[] args) throws Exception{
//准备数据
Name name1 = new Name("zhang","san");
Name name2 = new Name("li","si");
Name name3 = new Name("wang","wu");
Student student1 = newStudent(1,name1,"一班",newDate());
Student student2 = newStudent(2,name2,"二班",newDate());
Student student3 = newStudent(3,name3,"三班",newDate());
List<Student> studentList =new ArrayList<Student>();
studentList.add(student1);
studentList.add(student2);
studentList.add(student3);
Map<String,Student> studentMap =new HashMap<String, Student>();
studentMap.put("1",student1);
studentMap.put("2",student2);
studentMap.put("3",student3);
Student json2object = null;
List<Student> json2list =null;
Map<String,Student> json2map =null;
ObjectMapper mapper = getDefaultObjectMapper();
/* Object --> JSON */
String object4json = mapper.writeValueAsString(student1);
System.out.println("Object ----> JSON");
System.out.println(object4json);
System.out.println("------------------------------------------------------");
/* List<Object> --> JSON */
String listforjson = mapper.writeValueAsString(studentList);
System.out.println("List<Object> ----> JSON");
System.out.println(listforjson);
System.out.println("------------------------------------------------------");
/* Map<String,Object> ----> JSON */
String map4json = mapper.writeValueAsString(studentMap);
System.out.println("Map<String,Object> ----> JSON");
System.out.println(map4json);
System.out.println("------------------------------------------------------");
/* JSON --> Object */
json2object = mapper.readValue(object4json,Student.class);
System.out.println("JSON ----> Object");
System.out.println(json2object);
System.out.println("------------------------------------------------------");
/* JSON --> List<Object> */
json2list = mapper.readValue(listforjson, newTypeReference<List<Student>>() {});
System.out.println("JSON --> List<Object>");
System.out.println(json2list.toString());
System.out.println("------------------------------------------------------");
/* JSON --> Map<String,Object> */
json2map = mapper.readValue(map4json, newTypeReference<Map<String,Student>>() {});
System.out.println("JSON --> Map<String,Object>");
System.out.println(json2map.toString());
}
}
class Name{
private StringfirstName;
private StringlastName;
publicName(){}
publicName(StringfirstName, String lastName) {
this.firstName =firstName;
this.lastName =lastName;
}
public StringgetFirstName() {
returnfirstName;
}
public voidsetFirstName(String firstName) {
this.firstName =firstName;
}
public StringgetLastName() {
returnlastName;
}
public voidsetLastName(String lastName) {
this.lastName =lastName;
}
public StringtoString() {
returnfirstName + " " +lastName;
}
}
class Student{
private int id;
private Namename;
private StringclassName;
private DatebirthDay;
publicStudent(){}
publicStudent(intid, Name name, StringclassName, Date birthDay) {
super();
this.id =id;
this.name =name;
this.className =className;
this.birthDay =birthDay;
}
public int getId(){
returnid;
}
public void setId(intid) {
this.id =id;
}
public NamegetName() {
returnname;
}
public voidsetName(Name name) {
this.name =name;
}
public DategetBirthDay() {
returnbirthDay;
}
public voidsetBirthDay(Date birthDay) {
this.birthDay =birthDay;
}
public StringgetClassName() {
returnclassName;
}
public voidsetClassName(String className) {
this.className =className;
}
@Override
public StringtoString() {
return"Student [birthDay=" + birthDay + ",id=" + id + ", name=" + name + ",classname="+ className + "]";
}
}
/* 输出：
Object ---->JSON
{"id":1,"name":{"firstName":"zhang","lastName":"san"},"className":"一班","birthDay":"2016-08-2420:20:15"}
------------------------------------------------------
List<Object>----> JSON
[{"id":1,"name":{"firstName":"zhang","lastName":"san"},"className":"一班","birthDay":"2016-08-2420:20:15"},{"id":2,"name":{"firstName":"li","lastName":"si"},"className":"二班","birthDay":"2016-08-2420:20:15"},{"id":3,"name":{"firstName":"wang","lastName":"wu"},"className":"三班","birthDay":"2016-08-2420:20:15"}]
------------------------------------------------------
Map<String,Object> ----> JSON
{"3":{"id":3,"name":{"firstName":"wang","lastName":"wu"},"className":"三班","birthDay":"2016-08-2420:20:15"},"2":{"id":2,"name":{"firstName":"li","lastName":"si"},"className":"二班","birthDay":"2016-08-2420:20:15"},"1":{"id":1,"name":{"firstName":"zhang","lastName":"san"},"className":"一班","birthDay":"2016-08-2420:20:15"}}
------------------------------------------------------
JSON ---->Object
Student[birthDay=Wed Aug 24 20:20:15 CST 2016, id=1, name=zhang san,classname=一班]
------------------------------------------------------
JSON -->List<Object>
[Student[birthDay=Wed Aug 24 20:20:15 CST 2016, id=1, name=zhang san,classname=一班],Student [birthDay=WedAug 24 20:20:15 CST 2016, id=2, name=li si,classname=二班],Student [birthDay=WedAug 24 20:20:15 CST 2016, id=3, name=wang wu,classname=三班]]
------------------------------------------------------
JSON -->Map<String,Object>
{3=Student[birthDay=Wed Aug 24 20:20:15 CST 2016, id=3, name=wang wu,classname=三班],2=Student [birthDay=WedAug 24 20:20:15 CST 2016, id=2, name=li si,classname=二班],1=Student [birthDay=WedAug 24 20:20:15 CST 2016, id=1, name=zhangsan, classname=一班]}
*/
Jackson简单用法二：
importjava.io.File;
importjava.io.IOException;
importjava.io.InputStream;
importjava.io.OutputStream;
importjava.io.Reader;
importjava.io.Writer;
importjava.net.URL;
importjava.text.DateFormat;
importjava.text.SimpleDateFormat;
importorg.codehaus.jackson.JsonGenerationException;
importorg.codehaus.jackson.JsonParseException;
importorg.codehaus.jackson.map.DeserializationConfig;
importorg.codehaus.jackson.map.JsonMappingException;
importorg.codehaus.jackson.map.ObjectMapper;
importorg.codehaus.jackson.map.SerializationConfig;
importorg.codehaus.jackson.map.annotate.JsonSerialize;
/*
* ObjectMapper的readValue()方法：
<T> T readValue(byte[]src, Class<T> valueType)
<T> T readValue(byte[]src, JavaType valueType)
<T> T readValue(byte[]src, TypeReference valueTypeRef)
<T> T readValue(Filesrc, Class<T> valueType)
<T> T readValue(Filesrc, JavaType valueType)
<T> T readValue(Filesrc, TypeReference valueTypeRef)
<T> T readValue(InputStreamsrc, Class<T> valueType)
<T> T readValue(InputStreamsrc, JavaType valueType)
<T> T readValue(InputStreamsrc, TypeReference valueTypeRef)
<T> T readValue(JsonNoderoot, Class<T> valueType)
<T> T readValue(JsonNoderoot, JavaType valueType)
<T> T readValue(JsonNoderoot, TypeReference valueTypeRef)
<T> T readValue(JsonParserjp, Class<T> valueType)
<T> T readValue(Readersrc, Class<T> valueType)
<T> T readValue(Readersrc, JavaType valueType)
<T> T readValue(Readersrc, TypeReference valueTypeRef)
<T> T readValue(Stringcontent, Class<T> valueType)
<T> T readValue(Stringcontent, JavaType valueType)
<T> T readValue(Stringcontent, TypeReference valueTypeRef)
ObjectMapper的writeValue()方法：
void writeValue(File resultFile, Object value)
void writeValue(JsonGeneratorjgen, Object value)
void writeValue(JsonGeneratorjgen, Object value, SerializationConfigconfig)
void writeValue(OutputStreamout, Object value)
void writeValue(Writerw, Object value)
byte[] writeValueAsBytes(Objectvalue)
String writeValueAsString(Objectvalue)
*/
public classJsonFormatter {
private static finalThreadLocal<ObjectMapper>INCLUDE_NULL_MAPPER =new ThreadLocal();
private static finalThreadLocal<ObjectMapper>NOT_INCLUDE_NULL_MAPPER =new ThreadLocal();
private staticObjectMapper getMapper(booleanserializeNull) {
ThreadLocaltl =serializeNull ? INCLUDE_NULL_MAPPER :NOT_INCLUDE_NULL_MAPPER;//t1是引用变量，指向两者中的一个
if (null ==tl.get()){
ObjectMappermapper =new ObjectMapper();
mapper.disable(
newDeserializationConfig.Feature[] { DeserializationConfig.Feature.FAIL_ON_UNKNOWN_PROPERTIES });
mapper.setDateFormat(newSimpleDateFormat("yyyy-MM-dd"));
if (!serializeNull){ //不包括null时
mapper.setSerializationInclusion(JsonSerialize.Inclusion.NON_NULL);
mapper.disable(newSerializationConfig.Feature[] { SerializationConfig.Feature.WRITE_NULL_MAP_VALUES });
}
tl.set(mapper);
}
return(ObjectMapper)tl.get();
}
public static StringtoJsonString(Object obj)throws JsonGenerationException, JsonMappingException,IOException {
returntoJsonString(obj, true);
}
public static StringtoJsonAsString(Object obj)throws JsonGenerationException, JsonMappingException,IOException {
returntoJsonAsString(obj, true);
}
public static byte[]toJsonAsBytes(Objectobj) throws JsonGenerationException, JsonMappingException,IOException {
returntoJsonAsBytes(obj, true);
}
public static voidtoJsonToFile(File file, Object obj)
throwsJsonGenerationException, JsonMappingException, IOException {
toJsonToFile(file,obj, true);
}
public static voidtoJsonToOutputStream(OutputStreamout, Object obj)
throwsJsonGenerationException, JsonMappingException, IOException {
toJsonToOutputStream(out,obj, true);
}
public static voidtoJsonToWriter(Writerwriter, Object obj)
throwsJsonGenerationException, JsonMappingException, IOException {
toJsonToWriter(writer,obj, true);
}
public static<T> T toObject(String json, Class<T>clazz)
throwsJsonParseException, JsonMappingException, IOException {
returntoObject(json, clazz, true);
}
public static<T> T toObject(byte[]src, Class<T> clazz)
throwsJsonParseException, JsonMappingException, IOException {
returntoObject(src, clazz, true);
}
public static <T> T toObject(File file,Class<T>clazz)
throwsJsonParseException, JsonMappingException, IOException {
returntoObject(file, clazz, true);
}
public static<T> T toObject(InputStream input, Class<T>clazz)
throwsJsonParseException, JsonMappingException, IOException {
returntoObject(input, clazz, true);
}
public static<T> T toObject(Reader reader, Class<T>clazz)
throwsJsonParseException, JsonMappingException, IOException {
returntoObject(reader, clazz, true);
}
public static<T> T toObject(URL url, Class<T>clazz) throwsJsonParseException, JsonMappingException, IOException {
returntoObject(url, clazz, true);
}
public static StringtoJsonString(Object obj,boolean serializeNull)
throwsJsonGenerationException, JsonMappingException, IOException {
returngetMapper(serializeNull).writeValueAsString(obj); //Yue
}
public static StringtoJsonAsString(Object obj,boolean serializeNull)
throwsJsonGenerationException, JsonMappingException, IOException {
returngetMapper(serializeNull).writeValueAsString(obj); //Yue
}
public static byte[]toJsonAsBytes(Objectobj, booleanserializeNull)
throwsJsonGenerationException, JsonMappingException, IOException {
returngetMapper(serializeNull).writeValueAsBytes(obj); //Yue
}
public static voidtoJsonToFile(File file, Object obj, booleanserializeNull)
throwsJsonGenerationException, JsonMappingException, IOException {
getMapper(serializeNull).writeValue(file,obj); //Yue
}
public static voidtoJsonToOutputStream(OutputStreamout, Object obj,boolean serializeNull)
throwsJsonGenerationException, JsonMappingException, IOException {
getMapper(serializeNull).writeValue(out,obj); //Yue
}
public static voidtoJsonToWriter(Writerwriter, Object obj,boolean serializeNull)
throwsJsonGenerationException, JsonMappingException, IOException {
getMapper(serializeNull).writeValue(writer,obj); //Yue
}
//泛型方法的使用,为什么要使用泛型方法呢？因为泛型类要在实例化的时候就指明类型，如果想换一种类型，不得不重新new一次，可能不够灵活；而泛型方法可以在调用的时候指明类型，更加灵活。
// 需要注意，一个static方法，无法访问泛型类的类型参数，所以，若要static方法需要使用泛型能力，必须使其成为泛型方法。
public static<T> T toObject(String json, Class<T>clazz, booleanserializeNull)
throwsJsonParseException, JsonMappingException, IOException {
returngetMapper(serializeNull).readValue(json,clazz);
}
public static <T>T toObject(byte[]src, Class<T> clazz,boolean serializeNull)
throwsJsonParseException, JsonMappingException, IOException {
returngetMapper(serializeNull).readValue(src,clazz);
}
public static<T> T toObject(File file, Class<T>clazz, booleanserializeNull)
throwsJsonParseException, JsonMappingException, IOException {
returngetMapper(serializeNull).readValue(file,clazz);
}
public static<T> T toObject(InputStream input, Class<T>clazz, booleanserializeNull)
throwsJsonParseException, JsonMappingException, IOException {
returngetMapper(serializeNull).readValue(input,clazz);
}
public static<T> T toObject(Reader reader, Class<T>clazz, booleanserializeNull)
throwsJsonParseException, JsonMappingException, IOException {
returngetMapper(serializeNull).readValue(reader,clazz);
}
public static<T> T toObject(URL url, Class<T>clazz, booleanserializeNull)
throwsJsonParseException, JsonMappingException, IOException {
returngetMapper(serializeNull).readValue(url,clazz);
}
public static voidsetDateFormat(DateFormatdateFormat) {
getMapper(true).setDateFormat(dateFormat);
getMapper(false).setDateFormat(dateFormat);
}
}
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