# java实例json格式化-fastjson
使用这个包。进行json字符串与java实体对象的相互的转化。
<!-- json转换 -->
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>fastjson</artifactId>
<version>1.2.58</version>
</dependency>
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# 需求一
将如下的这个json格式的字符串转化为一个java实体对象。
{
"Tenants": [
{
"Code": "999999",
"DbOptions": {
"Type": "MySQL",
"ConnectionString": "Server=172.168.50.107;Persist Security Info=true;Uid=c3iot;Pwd=Das@c3iot_group;Database=c3_999999_xf;Port=3306;Charset=utf8mb4;"
}
}
]
}
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这个对象使用map集合存储。key为Code，value为这个对象。
{
"Code": "999999",
"DbOptions": {
"Type": "MySQL",
"ConnectionString": "Server=172.168.50.107;Persist Security Info=true;Uid=c3iot;Pwd=Das@c3iot_group;Database=c3_999999_xf;Port=3306;Charset=utf8mb4;"
}
}
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# 需求二
描述：
将json的字符串格式化。有格式的字符串。
# 需求三：创建一个用户
/**
* 创建默认对象
*/
@GetMapping("/fastjson01")
public void test01() {
User user = new User();
log.info("====>user:{}",user);
}
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# 需求四：创建一个组
/**
* 创建默认对象
*/
@GetMapping("/fastjson02")
public void test02() {
UserGroup userGroup = new UserGroup();
log.info("====>userGroup:{}",userGroup);
}
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# 需求五：对象转json
- 打印：创建多个用户放到一个组。打印组对象信息。
- 将对象转化为json字符串并且控制台打印显示。
@GetMapping("/fastjson03")
public void test03() {
// 构建用户geust
User guestUser = new User();
guestUser.setName("guest");
guestUser.setAge(28);
// 构建用户root
User rootUser = new User();
rootUser.setName("root");
guestUser.setAge(35);
// 构建用户组对象
UserGroup group = new UserGroup();
group.setName("admin");
group.getUsers().add(guestUser);
group.getUsers().add(rootUser);
System.out.println("group:" + group);
// 用户组对象转JSON串
String jsonString = JSON.toJSONString(group);
System.out.println("jsonString:" + jsonString);
}
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- 执行效果
# 需求六：json串转对象
// JSON串转用户组对象
UserGroup group2 = JSON.parseObject(jsonString, UserGroup.class);
System.out.println("JSON串转用户组对象:" + group2);
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# 需求七：数组转json串
// 构建用户对象数组
User[] users = new User[2];
users[0] = guestUser;
users[1] = rootUser;
// 用户对象数组转JSON串
String jsonString2 = JSON.toJSONString(users);
System.out.println("数组转json串:" + jsonString2);
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# 需求八：json串转数组
// JSON串转用户对象列表
List<User> users2 = JSON.parseArray(jsonString2, User.class);
System.out.println("json串转对象:" + users2);
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# 01)常见问题
# 问题描述
读取的json字符串里面有注释。无法解析正常的java对象。
com.fasterxml.jackson.core.JsonParseException: Unexpected character ('/' (code 47)): maybe a (non-standard) comment? (not recognized as one since Feature 'ALLOW_COMMENTS' not enabled for parser)
at [Source: (String)"{
//配置住户数组
"Tenants": [
{
"Code": "999999",
"DbOptions": {
"Type": "MySQL",
"ConnectionString": "Server=172.168.50.107;Persist Security Info=true;Uid=c3iot;Pwd=Das@c3iot_group;Database=c3_999999_fk;Port=3306;Charset=utf8mb4;"
}
}
]
}"; line: 2, column: 5]
at com.fasterxml.jackson.core.JsonParser._constructError(JsonParser.java:1851)
at com.fasterxml.jackson.core.base.ParserMinimalBase._reportError(ParserMinimalBase.java:707)
at com.fasterxml.jackson.core.base.ParserMinimalBase._reportUnexpectedChar(ParserMinimalBase.java:632)
at com.fasterxml.jackson.core.json.ReaderBasedJsonParser._skipComment(ReaderBasedJsonParser.java:2466)
at com.fasterxml.jackson.core.json.ReaderBasedJsonParser._skipWSOrEnd2(ReaderBasedJsonParser.java:2441)
at com.fasterxml.jackson.core.json.ReaderBasedJsonParser._skipWSOrEnd(ReaderBasedJsonParser.java:2412)
at com.fasterxml.jackson.core.json.ReaderBasedJsonParser.nextFieldName(ReaderBasedJsonParser.java:909)
at com.fasterxml.jackson.databind.deser.std.BaseNodeDeserializer.deserializeObject(JsonNodeDeserializer.java:249)
at com.fasterxml.jackson.databind.deser.std.JsonNodeDeserializer.deserialize(JsonNodeDeserializer.java:68)
at com.fasterxml.jackson.databind.deser.std.JsonNodeDeserializer.deserialize(JsonNodeDeserializer.java:15)
at com.fasterxml.jackson.databind.ObjectMapper._readTreeAndClose(ObjectMapper.java:4576)
at com.fasterxml.jackson.databind.ObjectMapper.readTree(ObjectMapper.java:2972)
at cn.csdas.biz.om.nacos.NacosHandler.parseAndPrint(NacosHandler.java:266)
at cn.csdas.biz.om.nacos.NacosHandler.alterNacosConfig(NacosHandler.java:92)
at cn.csdas.biz.om.tenant.controller.TenantManagerController.alterNacosConfig1(TenantManagerController.java:46)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:190)
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:138)
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:105)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:878)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:792)
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1040)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:909)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:652)
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:733)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.springframework.boot.actuate.metrics.web.servlet.WebMvcMetricsFilter.doFilterInternal(WebMvcMetricsFilter.java:93)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:541)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:143)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:374)
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1590)
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:745)
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