Add Jolokia agent in proxy mode

metricbeat/module/jolokia/jmx/_meta/docs.asciidoc

@@ -22,6 +22,10 @@ mapping:
       attributes:
         - attr: Uptime
           field: uptime
+      target:
+          url: "service:jmx:rmi:///jndi/rmi://targethost:9999/jmxrmi"
+          user: "jolokia"
+          password: "s!cr!t"
 ---
 
 In case the underlying attribute is an object (e.g. see HeapMemoryUsage attribute in java.lang:type=Memory) its

metricbeat/module/jolokia/jmx/config.go

@@ -5,13 +5,20 @@ import "encoding/json"
 type JMXMapping struct {
 	MBean      string
 	Attributes []Attribute
+	Target     Target
 }
 
 type Attribute struct {
 	Attr  string
 	Field string
 }
 
+type Target struct {
+	Url      string
+	User     string
+	Password string
+}
+
 // RequestBlock is used to build the request blocks of the following format:
 //
 // [
@@ -32,9 +39,16 @@ type Attribute struct {
 //    }
 // ]
 type RequestBlock struct {
-	Type      string   `json:"type"`
-	MBean     string   `json:"mbean"`
-	Attribute []string `json:"attribute"`
+	Type      string       `json:"type"`
+	MBean     string       `json:"mbean"`
+	Attribute []string     `json:"attribute"`
+	Target    *TargetBlock `json:"target,omitempty"`
+}
+
+type TargetBlock struct {
+	Url      string `json:"url"`
+	User     string `json:"user,omitempty"`
+	Password string `json:"password,omitempty"`
 }
 
 func buildRequestBodyAndMapping(mappings []JMXMapping) ([]byte, map[string]string, error) {
@@ -47,6 +61,13 @@ func buildRequestBodyAndMapping(mappings []JMXMapping) ([]byte, map[string]strin
 			MBean: mapping.MBean,
 		}
 
+		if len(mapping.Target.Url) != 0 {
+			rb.Target = new(TargetBlock)
+			rb.Target.Url = mapping.Target.Url
+			rb.Target.User = mapping.Target.User
+			rb.Target.Password = mapping.Target.Password
+		}
+
 		for _, attribute := range mapping.Attributes {
 			rb.Attribute = append(rb.Attribute, attribute.Attr)
 			responseMapping[mapping.MBean+"_"+attribute.Attr] = attribute.Field