<转>getResourceAsStream和getResource的用法

本文详细介绍了Java中使用getClass().getResourceAsStream()与getClass().getResource()方法来加载资源的具体方式及区别。通过示例代码展示了如何读取文件内容,并解释了路径指定的重要性。

getResourceAsStream:查找具有给定名称的资源。返回InputStream

getResource:查找带有给定名称的资源路径。返回URL

简单示例:(注:任何一个类都有一个getClass()的方法)

public class Test {
 public void getResource(String url){
  InputStream stream = getClass().getResourceAsStream(url);


  System.out.println(getClass().getResource(url));


  byte[] line = new byte[1024*1024];
  try {
   stream.read(line);
  } catch (IOException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }
  String str = new String(line);


  System.out.println(str.trim());


 }
 
 public static void main(String[] args) {
  new Test().getResource("/io/aaa.txt");
 }
}
运行结果:
file:/D:/IBM/workspace/HtmlParser/io/aaa.txt


abceefghijklmn

 


第一行得到的是aaa.txt的路径,

第二行是aaa.txt的内容。


需要注意的是必须有前面的“/”,代表的是工程目录,否则找不到。

 

 

 

 

import org.apache.ibatis.io.Resources; import org.apache.ibatis.session.SqlSession; import org.apache.ibatis.session.SqlSessionFactory; import org.apache.ibatis.session.SqlSessionFactoryBuilder; import java.io.IOException; import java.io.InputStream; import java.util.List; public class mbdemo { public static void main(String[] args) throws IOException { String resource = "mybatis-config.xml"; InputStream inputStream = Resources.getResourceAsStream(resource); SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream); SqlSession sqlSession = sqlSessionFactory.openSession(); sqlSession.selectOne("test.selectall"); List<Object> objects = sqlSession.selectList("test.selectall"); System.out.println(objects); sqlSession.close(); } } public class user { private Integer id; private String name_; private Integer age; private Integer birth; private Integer tall; public user(Integer id, String name_, Integer age, Integer birth, Integer tall) { this.id = id; this.name_ = name_; this.age = age; this.birth = birth; this.tall = tall; } @Override public String toString() { return "user{" + "id=" + id + ", name_='" + name_ + '\'' + ", age=" + age + ", birth=" + birth + ", tall=" + tall + '}'; } } <?xml version="1.0" encoding="UTF-8"?> <configuration> <!-- CONSOLE :表示当前的日志信息是可以输出到控制台的。 --> <appender name="Console" class="ch.qos.logback.core.ConsoleAppender"> <encoder> <pattern>[%level] %blue(%d{HH:mm:ss.SSS}) %cyan([%thread]) %boldGreen(%logger{15}) - %msg %n</pattern> </encoder> </appender> <logger name="com.itheima" level="DEBUG" additivity="false"> <appender-ref ref="Console"/> </logger> <!-- level:用来设置打印级别,大小写无关:TRACE, DEBUG, INFO, WARN, ERROR, ALL OFF , 默认debug <root>可以包含零个或多个<appender-ref>元素,标识这个输出位置将会被本日志级别控制。 --> <root level="DEBUG"> <appender-ref ref="Console"/> </root> </configuration><?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd"> <configuration> <environments default="development"> <environment id="development"> <transactionManager type="JDBC"/> <dataSource type="POOLED"> <!--数据库连接信息--> <property name="driver" value="com.mysql.jdbc.Driver"/> <property name="url" value="jdbc:mysql:///mybatis?useSSL=false"/> <property name="username" value="root"/> <property name="password" value="root"/> </dataSource> </environment> </environments> <mappers> <!--加载sql的映射文件--> <mapper resource="tablemapper.xml"/> </mappers> </configuration><?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd"> <!-- namespace 名称空间 --> <mapper namespace="test"> <select id="selectall" resultType="user"> select * from student; </select> </mapper><?xml version="1.0" encoding="UTF-8"?> <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>org.example</groupId> <artifactId>mybatis-demo</artifactId> <version>1.0-SNAPSHOT</version> <dependencies> <dependency> <groupId>org.mybatis</groupId> <artifactId>mybatis</artifactId> <version>3.5.5</version> </dependency> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>8.0.33</version> </dependency> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>4.13.1</version> <scope>test</scope> </dependency> <!-- 添加slf4j日志api --> <dependency> <groupId>org.slf4j</groupId> <artifactId>slf4j-api</artifactId> <version>1.7.20</version> </dependency> <!-- 添加logback-classic依赖 --> <dependency> <groupId>ch.qos.logback</groupId> <artifactId>logback-classic</artifactId> <version>1.2.3</version> </dependency> <!-- 添加logback-core依赖 --> <dependency> <groupId>ch.qos.logback</groupId> <artifactId>logback-core</artifactId> <version>1.2.3</version> </dependency> </dependencies> </project>"C:\Program Files\Java\jdk-1.8\bin\java.exe" "-javaagent:D:\idea\IntelliJ IDEA 2020.1.2\lib\idea_rt.jar=51781:D:\idea\IntelliJ IDEA 2020.1.2\bin" -Dfile.encoding=UTF-8 -classpath "C:\Program Files\Java\jdk-1.8\jre\lib\charsets.jar;C:\Program Files\Java\jdk-1.8\jre\lib\deploy.jar;C:\Program Files\Java\jdk-1.8\jre\lib\ext\access-bridge-64.jar;C:\Program Files\Java\jdk-1.8\jre\lib\ext\cldrdata.jar;C:\Program Files\Java\jdk-1.8\jre\lib\ext\dnsns.jar;C:\Program Files\Java\jdk-1.8\jre\lib\ext\jaccess.jar;C:\Program Files\Java\jdk-1.8\jre\lib\ext\jfxrt.jar;C:\Program Files\Java\jdk-1.8\jre\lib\ext\localedata.jar;C:\Program Files\Java\jdk-1.8\jre\lib\ext\nashorn.jar;C:\Program Files\Java\jdk-1.8\jre\lib\ext\sunec.jar;C:\Program Files\Java\jdk-1.8\jre\lib\ext\sunjce_provider.jar;C:\Program Files\Java\jdk-1.8\jre\lib\ext\sunmscapi.jar;C:\Program Files\Java\jdk-1.8\jre\lib\ext\sunpkcs11.jar;C:\Program Files\Java\jdk-1.8\jre\lib\ext\zipfs.jar;C:\Program Files\Java\jdk-1.8\jre\lib\javaws.jar;C:\Program Files\Java\jdk-1.8\jre\lib\jce.jar;C:\Program Files\Java\jdk-1.8\jre\lib\jfr.jar;C:\Program Files\Java\jdk-1.8\jre\lib\jfxswt.jar;C:\Program Files\Java\jdk-1.8\jre\lib\jsse.jar;C:\Program Files\Java\jdk-1.8\jre\lib\management-agent.jar;C:\Program Files\Java\jdk-1.8\jre\lib\plugin.jar;C:\Program Files\Java\jdk-1.8\jre\lib\resources.jar;C:\Program Files\Java\jdk-1.8\jre\lib\rt.jar;C:\Users\22844\IdeaProjects\mybatis-demo\target\classes;C:\Users\22844\.m2\repository\org\mybatis\mybatis\3.5.5\mybatis-3.5.5.jar;C:\Users\22844\.m2\repository\com\mysql\mysql-connector-j\8.0.33\mysql-connector-j-8.0.33.jar;C:\Users\22844\.m2\repository\com\google\protobuf\protobuf-java\3.21.9\protobuf-java-3.21.9.jar;C:\Users\22844\.m2\repository\org\slf4j\slf4j-api\1.7.20\slf4j-api-1.7.20.jar;C:\Users\22844\.m2\repository\ch\qos\logback\logback-classic\1.2.3\logback-classic-1.2.3.jar;C:\Users\22844\.m2\repository\ch\qos\logback\logback-core\1.2.3\logback-core-1.2.3.jar" mbdemo [DEBUG] 12:16:35.713 [main] o.a.i.l.LogFactory - Logging initialized using 'class org.apache.ibatis.logging.slf4j.Slf4jImpl' adapter. [DEBUG] 12:16:35.728 [main] o.a.i.d.p.PooledDataSource - PooledDataSource forcefully closed/removed all connections. [DEBUG] 12:16:35.728 [main] o.a.i.d.p.PooledDataSource - PooledDataSource forcefully closed/removed all connections. [DEBUG] 12:16:35.728 [main] o.a.i.d.p.PooledDataSource - PooledDataSource forcefully closed/removed all connections. [DEBUG] 12:16:35.728 [main] o.a.i.d.p.PooledDataSource - PooledDataSource forcefully closed/removed all connections. [DEBUG] 12:16:35.768 [main] o.a.i.t.j.JdbcTransaction - Opening JDBC Connection Loading class `com.mysql.jdbc.Driver'. This is deprecated. The new driver class is `com.mysql.cj.jdbc.Driver'. The driver is automatically registered via the SPI and manual loading of the driver class is generally unnecessary. Exception in thread "main" org.apache.ibatis.exceptions.PersistenceException: ### Error querying database. Cause: java.sql.SQLNonTransientConnectionException: Public Key Retrieval is not allowed ### The error may exist in tablemapper.xml ### The error may involve test.selectall ### The error occurred while executing a query ### Cause: java.sql.SQLNonTransientConnectionException: Public Key Retrieval is not allowed at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:30) at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:149) at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:140) at org.apache.ibatis.session.defaults.DefaultSqlSession.selectOne(DefaultSqlSession.java:76) at org.apache.ibatis.session.defaults.DefaultSqlSession.selectOne(DefaultSqlSession.java:70) at mbdemo.main(mbdemo.java:16) Caused by: java.sql.SQLNonTransientConnectionException: Public Key Retrieval is not allowed at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:111) at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:122) at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:825) at com.mysql.cj.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:446) at com.mysql.cj.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:239) at com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:188) at java.sql.DriverManager.getConnection(DriverManager.java:664) at java.sql.DriverManager.getConnection(DriverManager.java:208) at org.apache.ibatis.datasource.unpooled.UnpooledDataSource.doGetConnection(UnpooledDataSource.java:224) at org.apache.ibatis.datasource.unpooled.UnpooledDataSource.doGetConnection(UnpooledDataSource.java:219) at org.apache.ibatis.datasource.unpooled.UnpooledDataSource.getConnection(UnpooledDataSource.java:95) at org.apache.ibatis.datasource.pooled.PooledDataSource.popConnection(PooledDataSource.java:432) at org.apache.ibatis.datasource.pooled.PooledDataSource.getConnection(PooledDataSource.java:89) at org.apache.ibatis.transaction.jdbc.JdbcTransaction.openConnection(JdbcTransaction.java:139) at org.apache.ibatis.transaction.jdbc.JdbcTransaction.getConnection(JdbcTransaction.java:61) at org.apache.ibatis.executor.BaseExecutor.getConnection(BaseExecutor.java:337) at org.apache.ibatis.executor.SimpleExecutor.prepareStatement(SimpleExecutor.java:86) at org.apache.ibatis.executor.SimpleExecutor.doQuery(SimpleExecutor.java:62) at org.apache.ibatis.executor.BaseExecutor.queryFromDatabase(BaseExecutor.java:325) at org.apache.ibatis.executor.BaseExecutor.query(BaseExecutor.java:156) at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:109) at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:89) at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:147) ... 4 more Caused by: com.mysql.cj.exceptions.UnableToConnectException: Public Key Retrieval is not allowed at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) at java.lang.reflect.Constructor.newInstance(Constructor.java:423) at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:62) at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:86) at com.mysql.cj.protocol.a.authentication.CachingSha2PasswordPlugin.nextAuthenticationStep(CachingSha2PasswordPlugin.java:130) at com.mysql.cj.protocol.a.authentication.CachingSha2PasswordPlugin.nextAuthenticationStep(CachingSha2PasswordPlugin.java:49) at com.mysql.cj.protocol.a.NativeAuthenticationProvider.proceedHandshakeWithPluggableAuthentication(NativeAuthenticationProvider.java:443) at com.mysql.cj.protocol.a.NativeAuthenticationProvider.connect(NativeAuthenticationProvider.java:213) at com.mysql.cj.protocol.a.NativeProtocol.connect(NativeProtocol.java:1430) at com.mysql.cj.NativeSession.connect(NativeSession.java:134) at com.mysql.cj.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:945) at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:815) ... 24 more Process finished with exit code 1
05-12
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