Java tutorial
/* * Copyright (c) 2014 Baidu.com, Inc. All Rights Reserved * * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with * the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the * specific language governing permissions and limitations under the License. */ package com.baidubce.util; import java.io.File; import java.io.IOException; import java.io.InputStream; import java.io.Writer; import com.baidubce.BceClientException; import com.fasterxml.jackson.annotation.JsonInclude.Include; import com.fasterxml.jackson.core.JsonFactory; import com.fasterxml.jackson.core.JsonGenerator; import com.fasterxml.jackson.core.JsonParseException; import com.fasterxml.jackson.core.JsonParser; import com.fasterxml.jackson.core.JsonProcessingException; import com.fasterxml.jackson.databind.DeserializationFeature; import com.fasterxml.jackson.databind.SerializationFeature; import com.fasterxml.jackson.databind.JsonMappingException; import com.fasterxml.jackson.databind.JsonNode; import com.fasterxml.jackson.databind.ObjectMapper; import com.fasterxml.jackson.databind.ObjectWriter; public class JsonUtils { private static final ObjectMapper objectMapper = new ObjectMapper(); static { JsonUtils.objectMapper.configure(SerializationFeature.FAIL_ON_EMPTY_BEANS, false); JsonUtils.objectMapper.configure(JsonParser.Feature.ALLOW_COMMENTS, true); JsonUtils.objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false); JsonUtils.objectMapper.setSerializationInclusion(Include.NON_NULL); } private static final ObjectWriter writer = JsonUtils.objectMapper.writer(); private static final ObjectWriter prettyWriter = JsonUtils.objectMapper.writerWithDefaultPrettyPrinter(); public static String toJsonPrettyString(Object value) throws JsonProcessingException { return JsonUtils.prettyWriter.writeValueAsString(value); } public static String toJsonString(Object value) { try { return JsonUtils.writer.writeValueAsString(value); } catch (Exception e) { throw new IllegalStateException(e); } } /** * Returns the deserialized object from the given json string and target class; or null if the given json string is * null. */ public static <T> T fromJsonString(String json, Class<T> clazz) { if (json == null) { return null; } try { return JsonUtils.objectMapper.readValue(json, clazz); } catch (Exception e) { throw new BceClientException("Unable to parse Json String.", e); } } public static JsonNode jsonNodeOf(String json) { return JsonUtils.fromJsonString(json, JsonNode.class); } public static JsonGenerator jsonGeneratorOf(Writer writer) throws IOException { return new JsonFactory().createGenerator(writer); } public static <T> T loadFrom(File file, Class<T> clazz) throws IOException { try { return JsonUtils.objectMapper.readValue(file, clazz); } catch (IOException e) { throw e; } catch (Exception e) { throw new IllegalStateException(e); } } public static void load(InputStream input, Object obj) throws IOException, JsonProcessingException { objectMapper.readerForUpdating(obj).readValue(input); } public static <T> T loadFrom(InputStream input, Class<T> clazz) throws JsonParseException, JsonMappingException, IOException { return JsonUtils.objectMapper.readValue(input, clazz); } public static ObjectMapper getObjectMapper() { return JsonUtils.objectMapper; } public static ObjectWriter getWriter() { return JsonUtils.writer; } public static ObjectWriter getPrettywriter() { return JsonUtils.prettyWriter; } }